2307 Commits

Author SHA1 Message Date
Sean Christopherson
dc87275f47 KVM: x86: Move (most) SMM hflags modifications into kvm_smm_changed()
Move the core of SMM hflags modifications into kvm_smm_changed() and use
kvm_smm_changed() in enter_smm().  Clear HF_SMM_INSIDE_NMI_MASK for
leaving SMM but do not set it for entering SMM.  If the vCPU is executing
outside of SMM, the flag should unequivocally be cleared, e.g. this
technically fixes a benign bug where the flag could be left set after
KVM_SET_VCPU_EVENTS, but the reverse is not true as NMI blocking depends
on pre-SMM state or userspace input.

Note, this adds an extra kvm_mmu_reset_context() to enter_smm().  The
extra/early reset isn't strictly necessary, and in a way can never be
necessary since the vCPU/MMU context is in a half-baked state until the
final context reset at the end of the function.  But, enter_smm() is not
a hot path, and exploding on an invalid root_hpa is probably better than
having a stale SMM flag in the MMU role; it's at least no worse.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609185619.992058-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:34 -04:00
Sean Christopherson
fa75e08bbe KVM: x86: Invoke kvm_smm_changed() immediately after clearing SMM flag
Move RSM emulation's call to kvm_smm_changed() from .post_leave_smm() to
.exiting_smm(), leaving behind the MMU context reset.  The primary
motivation is to allow for future cleanup, but this also fixes a bug of
sorts by queueing KVM_REQ_EVENT even if RSM causes shutdown, e.g. to let
an INIT wake the vCPU from shutdown.  Of course, KVM doesn't properly
emulate a shutdown state, e.g. KVM doesn't block SMIs after shutdown, and
immediately exits to userspace, so the event request is a moot point in
practice.

Moving kvm_smm_changed() also moves the RSM tracepoint.  This isn't
strictly necessary, but will allow consolidating the SMI and RSM
tracepoints in a future commit (by also moving the SMI tracepoint).
Invoking the tracepoint before loading SMRAM state also means the SMBASE
that reported in the tracepoint will point that the state that will be
used for RSM, as opposed to the SMBASE _after_ RSM completes, which is
arguably a good thing if the tracepoint is being used to debug a RSM/SMM
issue.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609185619.992058-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:34 -04:00
Sean Christopherson
edce46548b KVM: x86: Replace .set_hflags() with dedicated .exiting_smm() helper
Replace the .set_hflags() emulator hook with a dedicated .exiting_smm(),
moving the SMM and SMM_INSIDE_NMI flag handling out of the emulator in
the process.  This is a step towards consolidating much of the logic in
kvm_smm_changed(), including the SMM hflags updates.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609185619.992058-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:34 -04:00
Sean Christopherson
25b17226cd KVM: x86: Emulate triple fault shutdown if RSM emulation fails
Use the recently introduced KVM_REQ_TRIPLE_FAULT to properly emulate
shutdown if RSM from SMM fails.

Note, entering shutdown after clearing the SMM flag and restoring NMI
blocking is architecturally correct with respect to AMD's APM, which KVM
also uses for SMRAM layout and RSM NMI blocking behavior.  The APM says:

  An RSM causes a processor shutdown if an invalid-state condition is
  found in the SMRAM state-save area. Only an external reset, external
  processor-initialization, or non-maskable external interrupt (NMI) can
  cause the processor to leave the shutdown state.

Of note is processor-initialization (INIT) as a valid shutdown wake
event, as INIT is blocked by SMM, implying that entering shutdown also
forces the CPU out of SMM.

For recent Intel CPUs, restoring NMI blocking is technically wrong, but
so is restoring NMI blocking in the first place, and Intel's RSM
"architecture" is such a mess that just about anything is allowed and can
be justified as micro-architectural behavior.

Per the SDM:

  On Pentium 4 and later processors, shutdown will inhibit INTR and A20M
  but will not change any of the other inhibits. On these processors,
  NMIs will be inhibited if no action is taken in the SMI handler to
  uninhibit them (see Section 34.8).

where Section 34.8 says:

  When the processor enters SMM while executing an NMI handler, the
  processor saves the SMRAM state save map but does not save the
  attribute to keep NMI interrupts disabled. Potentially, an NMI could be
  latched (while in SMM or upon exit) and serviced upon exit of SMM even
  though the previous NMI handler has still not completed.

I.e. RSM unconditionally unblocks NMI, but shutdown on RSM does not,
which is in direct contradiction of KVM's behavior.  But, as mentioned
above, KVM follows AMD architecture and restores NMI blocking on RSM, so
that micro-architectural detail is already lost.

And for Pentium era CPUs, SMI# can break shutdown, meaning that at least
some Intel CPUs fully leave SMM when entering shutdown:

  In the shutdown state, Intel processors stop executing instructions
  until a RESET#, INIT# or NMI# is asserted.  While Pentium family
  processors recognize the SMI# signal in shutdown state, P6 family and
  Intel486 processors do not.

In other words, the fact that Intel CPUs have implemented the two
extremes gives KVM carte blanche when it comes to honoring Intel's
architecture for handling shutdown during RSM.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609185619.992058-3-seanjc@google.com>
[Return X86EMUL_CONTINUE after triple fault. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:33 -04:00
Vitaly Kuznetsov
4651fc56ba KVM: x86: Drop vendor specific functions for APICv/AVIC enablement
Now that APICv/AVIC enablement is kept in common 'enable_apicv' variable,
there's no need to call kvm_apicv_init() from vendor specific code.

No functional change intended.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210609150911.1471882-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:33 -04:00
Vitaly Kuznetsov
fdf513e37a KVM: x86: Use common 'enable_apicv' variable for both APICv and AVIC
Unify VMX and SVM code by moving APICv/AVIC enablement tracking to common
'enable_apicv' variable. Note: unlike APICv, AVIC is disabled by default.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210609150911.1471882-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:33 -04:00
Sergey Senozhatsky
7d62874f69 kvm: x86: implement KVM PM-notifier
Implement PM hibernation/suspend prepare notifiers so that KVM
can reliably set PVCLOCK_GUEST_STOPPED on VCPUs and properly
suspend VMs.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Message-Id: <20210606021045.14159-2-senozhatsky@chromium.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:33 -04:00
Jim Mattson
4fe09bcf14 KVM: x86: Add a return code to kvm_apic_accept_events
No functional change intended. At present, the only negative value
returned by kvm_check_nested_events is -EBUSY.

Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20210604172611.281819-6-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:31 -04:00
Jim Mattson
a5f6909a71 KVM: x86: Add a return code to inject_pending_event
No functional change intended. At present, 'r' will always be -EBUSY
on a control transfer to the 'out' label.

Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20210604172611.281819-5-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:30 -04:00
Jim Mattson
d82ee28195 KVM: x86: Remove guest mode check from kvm_check_nested_events
A survey of the callsites reveals that they all ensure the vCPU is in
guest mode before calling kvm_check_nested_events. Remove this dead
code so that the only negative value this function returns (at the
moment) is -EBUSY.

Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20210604172611.281819-2-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:30 -04:00
Ilias Stamatis
1ab9287add KVM: X86: Add vendor callbacks for writing the TSC multiplier
Currently vmx_vcpu_load_vmcs() writes the TSC_MULTIPLIER field of the
VMCS every time the VMCS is loaded. Instead of doing this, set this
field from common code on initialization and whenever the scaling ratio
changes.

Additionally remove vmx->current_tsc_ratio. This field is redundant as
vcpu->arch.tsc_scaling_ratio already tracks the current TSC scaling
ratio. The vmx->current_tsc_ratio field is only used for avoiding
unnecessary writes but it is no longer needed after removing the code
from the VMCS load path.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Message-Id: <20210607105438.16541-1-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:29 -04:00
Ilias Stamatis
edcfe54058 KVM: X86: Move write_l1_tsc_offset() logic to common code and rename it
The write_l1_tsc_offset() callback has a misleading name. It does not
set L1's TSC offset, it rather updates the current TSC offset which
might be different if a nested guest is executing. Additionally, both
the vmx and svm implementations use the same logic for calculating the
current TSC before writing it to hardware.

Rename the function and move the common logic to the caller. The vmx/svm
specific code now merely sets the given offset to the corresponding
hardware structure.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210526184418.28881-9-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:29 -04:00
Ilias Stamatis
83150f2932 KVM: X86: Add functions that calculate the nested TSC fields
When L2 is entered we need to "merge" the TSC multiplier and TSC offset
values of 01 and 12 together.

The merging is done using the following equations:
  offset_02 = ((offset_01 * mult_12) >> shift_bits) + offset_12
  mult_02 = (mult_01 * mult_12) >> shift_bits

Where shift_bits is kvm_tsc_scaling_ratio_frac_bits.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210526184418.28881-8-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:29 -04:00
Ilias Stamatis
fe3eb50418 KVM: X86: Add a ratio parameter to kvm_scale_tsc()
Sometimes kvm_scale_tsc() needs to use the current scaling ratio and
other times (like when reading the TSC from user space) it needs to use
L1's scaling ratio. Have the caller specify this by passing the ratio as
a parameter.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210526184418.28881-5-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:28 -04:00
Ilias Stamatis
9b399dfd4c KVM: X86: Rename kvm_compute_tsc_offset() to kvm_compute_l1_tsc_offset()
All existing code uses kvm_compute_tsc_offset() passing L1 TSC values to
it. Let's document this by renaming it to kvm_compute_l1_tsc_offset().

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210526184418.28881-4-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:28 -04:00
Ilias Stamatis
805d705ff8 KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu_arch'
Store L1's scaling ratio in the kvm_vcpu_arch struct like we already do
for L1's TSC offset. This allows for easy save/restore when we enter and
then exit the nested guest.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210526184418.28881-3-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:27 -04:00
Ben Gardon
d501f747ef KVM: x86/mmu: Lazily allocate memslot rmaps
If the TDP MMU is in use, wait to allocate the rmaps until the shadow
MMU is actually used. (i.e. a nested VM is launched.) This saves memory
equal to 0.2% of guest memory in cases where the TDP MMU is used and
there are no nested guests involved.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:27 -04:00
Ben Gardon
e2209710cc KVM: x86/mmu: Skip rmap operations if rmaps not allocated
If only the TDP MMU is being used to manage the memory mappings for a VM,
then many rmap operations can be skipped as they are guaranteed to be
no-ops. This saves some time which would be spent on the rmap operation.
It also avoids acquiring the MMU lock in write mode for many operations.

This makes it safe to run the VM without rmaps allocated, when only
using the TDP MMU and sets the stage for waiting to allocate the rmaps
until they're needed.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-7-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:26 -04:00
Ben Gardon
a255740876 KVM: x86/mmu: Add a field to control memslot rmap allocation
Add a field to control whether new memslots should have rmaps allocated
for them. As of this change, it's not safe to skip allocating rmaps, so
the field is always set to allocate rmaps. Future changes will make it
safe to operate without rmaps, using the TDP MMU. Then further changes
will allow the rmaps to be allocated lazily when needed for nested
oprtation.

No functional change expected.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-6-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:26 -04:00
Ben Gardon
56dd1019c8 KVM: x86/mmu: Factor out allocating memslot rmap
Small refactor to facilitate allocating rmaps for all memslots at once.

No functional change expected.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-3-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:25 -04:00
Ben Gardon
c9b929b3fa KVM: x86/mmu: Deduplicate rmap freeing
Small code deduplication. No functional change expected.

Reviewed-by: David Hildenbrand <david@redhat.com>

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-2-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:25 -04:00
Keqian Zhu
8921291980 KVM: x86: Do not write protect huge page in initially-all-set mode
Currently, when dirty logging is started in initially-all-set mode,
we write protect huge pages to prepare for splitting them into
4K pages, and leave normal pages untouched as the logging will
be enabled lazily as dirty bits are cleared.

However, enabling dirty logging lazily is also feasible for huge pages.
This not only reduces the time of start dirty logging, but it also
greatly reduces side-effect on guest when there is high dirty rate.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Message-Id: <20210429034115.35560-3-zhukeqian1@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-17 13:09:25 -04:00
Wanpeng Li
dfdc0a714d KVM: X86: Fix x86_emulator slab cache leak
Commit c9b8b07cded58 (KVM: x86: Dynamically allocate per-vCPU emulation context)
tries to allocate per-vCPU emulation context dynamically, however, the
x86_emulator slab cache is still exiting after the kvm module is unload
as below after destroying the VM and unloading the kvm module.

grep x86_emulator /proc/slabinfo
x86_emulator          36     36   2672   12    8 : tunables    0    0    0 : slabdata      3      3      0

This patch fixes this slab cache leak by destroying the x86_emulator slab cache
when the kvm module is unloaded.

Fixes: c9b8b07cded58 (KVM: x86: Dynamically allocate per-vCPU emulation context)
Cc: stable@vger.kernel.org
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1623387573-5969-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-11 11:53:48 -04:00
Sean Christopherson
78fcb2c91a KVM: x86: Immediately reset the MMU context when the SMM flag is cleared
Immediately reset the MMU context when the vCPU's SMM flag is cleared so
that the SMM flag in the MMU role is always synchronized with the vCPU's
flag.  If RSM fails (which isn't correctly emulated), KVM will bail
without calling post_leave_smm() and leave the MMU in a bad state.

The bad MMU role can lead to a NULL pointer dereference when grabbing a
shadow page's rmap for a page fault as the initial lookups for the gfn
will happen with the vCPU's SMM flag (=0), whereas the rmap lookup will
use the shadow page's SMM flag, which comes from the MMU (=1).  SMM has
an entirely different set of memslots, and so the initial lookup can find
a memslot (SMM=0) and then explode on the rmap memslot lookup (SMM=1).

  general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
  CPU: 1 PID: 8410 Comm: syz-executor382 Not tainted 5.13.0-rc5-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:__gfn_to_rmap arch/x86/kvm/mmu/mmu.c:935 [inline]
  RIP: 0010:gfn_to_rmap+0x2b0/0x4d0 arch/x86/kvm/mmu/mmu.c:947
  Code: <42> 80 3c 20 00 74 08 4c 89 ff e8 f1 79 a9 00 4c 89 fb 4d 8b 37 44
  RSP: 0018:ffffc90000ffef98 EFLAGS: 00010246
  RAX: 0000000000000000 RBX: ffff888015b9f414 RCX: ffff888019669c40
  RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
  RBP: 0000000000000001 R08: ffffffff811d9cdb R09: ffffed10065a6002
  R10: ffffed10065a6002 R11: 0000000000000000 R12: dffffc0000000000
  R13: 0000000000000003 R14: 0000000000000001 R15: 0000000000000000
  FS:  000000000124b300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000000 CR3: 0000000028e31000 CR4: 00000000001526e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   rmap_add arch/x86/kvm/mmu/mmu.c:965 [inline]
   mmu_set_spte+0x862/0xe60 arch/x86/kvm/mmu/mmu.c:2604
   __direct_map arch/x86/kvm/mmu/mmu.c:2862 [inline]
   direct_page_fault+0x1f74/0x2b70 arch/x86/kvm/mmu/mmu.c:3769
   kvm_mmu_do_page_fault arch/x86/kvm/mmu.h:124 [inline]
   kvm_mmu_page_fault+0x199/0x1440 arch/x86/kvm/mmu/mmu.c:5065
   vmx_handle_exit+0x26/0x160 arch/x86/kvm/vmx/vmx.c:6122
   vcpu_enter_guest+0x3bdd/0x9630 arch/x86/kvm/x86.c:9428
   vcpu_run+0x416/0xc20 arch/x86/kvm/x86.c:9494
   kvm_arch_vcpu_ioctl_run+0x4e8/0xa40 arch/x86/kvm/x86.c:9722
   kvm_vcpu_ioctl+0x70f/0xbb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3460
   vfs_ioctl fs/ioctl.c:51 [inline]
   __do_sys_ioctl fs/ioctl.c:1069 [inline]
   __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055
   do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
   entry_SYSCALL_64_after_hwframe+0x44/0xae
  RIP: 0033:0x440ce9

Cc: stable@vger.kernel.org
Reported-by: syzbot+fb0b6a7e8713aeb0319c@syzkaller.appspotmail.com
Fixes: 9ec19493fb86 ("KVM: x86: clear SMM flags before loading state while leaving SMM")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609185619.992058-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-10 09:21:12 -04:00
Linus Torvalds
2f673816b2 Bugfixes, including a TLB flush fix that affects processors
without nested page tables.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:
 "Bugfixes, including a TLB flush fix that affects processors without
  nested page tables"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  kvm: fix previous commit for 32-bit builds
  kvm: avoid speculation-based attacks from out-of-range memslot accesses
  KVM: x86: Unload MMU on guest TLB flush if TDP disabled to force MMU sync
  KVM: x86: Ensure liveliness of nested VM-Enter fail tracepoint message
  selftests: kvm: Add support for customized slot0 memory size
  KVM: selftests: introduce P47V64 for s390x
  KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior
  KVM: X86: MMU: Use the correct inherited permissions to get shadow page
  KVM: LAPIC: Write 0 to TMICT should also cancel vmx-preemption timer
  KVM: SVM: Fix SEV SEND_START session length & SEND_UPDATE_DATA query length after commit 238eca821cee
2021-06-09 13:09:57 -07:00
Lai Jiangshan
b53e84eed0 KVM: x86: Unload MMU on guest TLB flush if TDP disabled to force MMU sync
When using shadow paging, unload the guest MMU when emulating a guest TLB
flush to ensure all roots are synchronized.  From the guest's perspective,
flushing the TLB ensures any and all modifications to its PTEs will be
recognized by the CPU.

Note, unloading the MMU is overkill, but is done to mirror KVM's existing
handling of INVPCID(all) and ensure the bug is squashed.  Future cleanup
can be done to more precisely synchronize roots when servicing a guest
TLB flush.

If TDP is enabled, synchronizing the MMU is unnecessary even if nested
TDP is in play, as a "legacy" TLB flush from L1 does not invalidate L1's
TDP mappings.  For EPT, an explicit INVEPT is required to invalidate
guest-physical mappings; for NPT, guest mappings are always tagged with
an ASID and thus can only be invalidated via the VMCB's ASID control.

This bug has existed since the introduction of KVM_VCPU_FLUSH_TLB.
It was only recently exposed after Linux guests stopped flushing the
local CPU's TLB prior to flushing remote TLBs (see commit 4ce94eabac16,
"x86/mm/tlb: Flush remote and local TLBs concurrently"), but is also
visible in Windows 10 guests.

Tested-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Fixes: f38a7b75267f ("KVM: X86: support paravirtualized help for TLB shootdowns")
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
[sean: massaged comment and changelog]
Message-Id: <20210531172256.2908-1-jiangshanlai@gmail.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-08 17:10:21 -04:00
Lai Jiangshan
af3511ff7f KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior
In record_steal_time(), st->preempted is read twice, and
trace_kvm_pv_tlb_flush() might output result inconsistent if
kvm_vcpu_flush_tlb_guest() see a different st->preempted later.

It is a very trivial problem and hardly has actual harm and can be
avoided by reseting and reading st->preempted in atomic way via xchg().

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>

Message-Id: <20210531174628.10265-1-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-08 13:15:20 -04:00
Linus Torvalds
224478289c ARM fixes:
* Another state update on exit to userspace fix
 
 * Prevent the creation of mixed 32/64 VMs
 
 * Fix regression with irqbypass not restarting the guest on failed connect
 
 * Fix regression with debug register decoding resulting in overlapping access
 
 * Commit exception state on exit to usrspace
 
 * Fix the MMU notifier return values
 
 * Add missing 'static' qualifiers in the new host stage-2 code
 
 x86 fixes:
 * fix guest missed wakeup with assigned devices
 
 * fix WARN reported by syzkaller
 
 * do not use BIT() in UAPI headers
 
 * make the kvm_amd.avic parameter bool
 
 PPC fixes:
 * make halt polling heuristics consistent with other architectures
 
 selftests:
 * various fixes
 
 * new performance selftest memslot_perf_test
 
 * test UFFD minor faults in demand_paging_test
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull KVM fixes from Paolo Bonzini:
 "ARM fixes:

   - Another state update on exit to userspace fix

   - Prevent the creation of mixed 32/64 VMs

   - Fix regression with irqbypass not restarting the guest on failed
     connect

   - Fix regression with debug register decoding resulting in
     overlapping access

   - Commit exception state on exit to usrspace

   - Fix the MMU notifier return values

   - Add missing 'static' qualifiers in the new host stage-2 code

  x86 fixes:

   - fix guest missed wakeup with assigned devices

   - fix WARN reported by syzkaller

   - do not use BIT() in UAPI headers

   - make the kvm_amd.avic parameter bool

  PPC fixes:

   - make halt polling heuristics consistent with other architectures

  selftests:

   - various fixes

   - new performance selftest memslot_perf_test

   - test UFFD minor faults in demand_paging_test"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (44 commits)
  selftests: kvm: fix overlapping addresses in memslot_perf_test
  KVM: X86: Kill off ctxt->ud
  KVM: X86: Fix warning caused by stale emulation context
  KVM: X86: Use kvm_get_linear_rip() in single-step and #DB/#BP interception
  KVM: x86/mmu: Fix comment mentioning skip_4k
  KVM: VMX: update vcpu posted-interrupt descriptor when assigning device
  KVM: rename KVM_REQ_PENDING_TIMER to KVM_REQ_UNBLOCK
  KVM: x86: add start_assignment hook to kvm_x86_ops
  KVM: LAPIC: Narrow the timer latency between wait_lapic_expire and world switch
  selftests: kvm: do only 1 memslot_perf_test run by default
  KVM: X86: Use _BITUL() macro in UAPI headers
  KVM: selftests: add shared hugetlbfs backing source type
  KVM: selftests: allow using UFFD minor faults for demand paging
  KVM: selftests: create alias mappings when using shared memory
  KVM: selftests: add shmem backing source type
  KVM: selftests: refactor vm_mem_backing_src_type flags
  KVM: selftests: allow different backing source types
  KVM: selftests: compute correct demand paging size
  KVM: selftests: simplify setup_demand_paging error handling
  KVM: selftests: Print a message if /dev/kvm is missing
  ...
2021-05-29 06:02:25 -10:00
Wanpeng Li
b35491e66c KVM: X86: Kill off ctxt->ud
ctxt->ud is consumed only by x86_decode_insn(), we can kill it off by
passing emulation_type to x86_decode_insn() and dropping ctxt->ud
altogether. Tracking that info in ctxt for literally one call is silly.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <1622160097-37633-2-git-send-email-wanpengli@tencent.com>
2021-05-28 12:59:10 -04:00
Wanpeng Li
da6393cdd8 KVM: X86: Fix warning caused by stale emulation context
Reported by syzkaller:

  WARNING: CPU: 7 PID: 10526 at linux/arch/x86/kvm//x86.c:7621 x86_emulate_instruction+0x41b/0x510 [kvm]
  RIP: 0010:x86_emulate_instruction+0x41b/0x510 [kvm]
  Call Trace:
   kvm_mmu_page_fault+0x126/0x8f0 [kvm]
   vmx_handle_exit+0x11e/0x680 [kvm_intel]
   vcpu_enter_guest+0xd95/0x1b40 [kvm]
   kvm_arch_vcpu_ioctl_run+0x377/0x6a0 [kvm]
   kvm_vcpu_ioctl+0x389/0x630 [kvm]
   __x64_sys_ioctl+0x8e/0xd0
   do_syscall_64+0x3c/0xb0
   entry_SYSCALL_64_after_hwframe+0x44/0xae

Commit 4a1e10d5b5d8 ("KVM: x86: handle hardware breakpoints during emulation())
adds hardware breakpoints check before emulation the instruction and parts of
emulation context initialization, actually we don't have the EMULTYPE_NO_DECODE flag
here and the emulation context will not be reused. Commit c8848cee74ff ("KVM: x86:
set ctxt->have_exception in x86_decode_insn()) triggers the warning because it
catches the stale emulation context has #UD, however, it is not during instruction
decoding which should result in EMULATION_FAILED. This patch fixes it by moving
the second part emulation context initialization into init_emulate_ctxt() and
before hardware breakpoints check. The ctxt->ud will be dropped by a follow-up
patch.

syzkaller source: https://syzkaller.appspot.com/x/repro.c?x=134683fdd00000

Reported-by: syzbot+71271244f206d17f6441@syzkaller.appspotmail.com
Fixes: 4a1e10d5b5d8 (KVM: x86: handle hardware breakpoints during emulation)
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <1622160097-37633-1-git-send-email-wanpengli@tencent.com>
2021-05-28 12:59:09 -04:00
Yuan Yao
e87e46d5f3 KVM: X86: Use kvm_get_linear_rip() in single-step and #DB/#BP interception
The kvm_get_linear_rip() handles x86/long mode cases well and has
better readability, __kvm_set_rflags() also use the paired
function kvm_is_linear_rip() to check the vcpu->arch.singlestep_rip
set in kvm_arch_vcpu_ioctl_set_guest_debug(), so change the
"CS.BASE + RIP" code in kvm_arch_vcpu_ioctl_set_guest_debug() and
handle_exception_nmi() to this one.

Signed-off-by: Yuan Yao <yuan.yao@intel.com>
Message-Id: <20210526063828.1173-1-yuan.yao@linux.intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-28 12:57:53 -04:00
Marcelo Tosatti
084071d5e9 KVM: rename KVM_REQ_PENDING_TIMER to KVM_REQ_UNBLOCK
KVM_REQ_UNBLOCK will be used to exit a vcpu from
its inner vcpu halt emulation loop.

Rename KVM_REQ_PENDING_TIMER to KVM_REQ_UNBLOCK, switch
PowerPC to arch specific request bit.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Message-Id: <20210525134321.303768132@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-27 07:57:38 -04:00
Marcelo Tosatti
57ab87947a KVM: x86: add start_assignment hook to kvm_x86_ops
Add a start_assignment hook to kvm_x86_ops, which is called when
kvm_arch_start_assignment is done.

The hook is required to update the wakeup vector of a sleeping vCPU
when a device is assigned to the guest.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Message-Id: <20210525134321.254128742@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-27 07:50:13 -04:00
Wanpeng Li
1eff0ada88 KVM: X86: Fix vCPU preempted state from guest's point of view
Commit 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's
CPUID) avoids to access pv tlb shootdown host side logic when this pv feature
is not exposed to guest, however, kvm_steal_time.preempted not only leveraged
by pv tlb shootdown logic but also mitigate the lock holder preemption issue.
From guest's point of view, vCPU is always preempted since we lose the reset
of kvm_steal_time.preempted before vmentry if pv tlb shootdown feature is not
exposed. This patch fixes it by clearing kvm_steal_time.preempted before
vmentry.

Fixes: 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID)
Reviewed-by: Sean Christopherson <seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1621339235-11131-3-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-27 07:45:53 -04:00
Wanpeng Li
72b268a8e9 KVM: X86: Bail out of direct yield in case of under-committed scenarios
In case of under-committed scenarios, vCPUs can be scheduled easily;
kvm_vcpu_yield_to adds extra overhead, and it is also common to see
when vcpu->ready is true but yield later failing due to p->state is
TASK_RUNNING.

Let's bail out in such scenarios by checking the length of current cpu
runqueue, which can be treated as a hint of under-committed instead of
guarantee of accuracy. 30%+ of directed-yield attempts can now avoid
the expensive lookups in kvm_sched_yield() in an under-committed scenario.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1621339235-11131-2-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-27 07:45:52 -04:00
Paolo Bonzini
a4345a7cec KVM/arm64 fixes for 5.13, take #1
- Fix regression with irqbypass not restarting the guest on failed connect
 - Fix regression with debug register decoding resulting in overlapping access
 - Commit exception state on exit to usrspace
 - Fix the MMU notifier return values
 - Add missing 'static' qualifiers in the new host stage-2 code
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Merge tag 'kvmarm-fixes-5.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

KVM/arm64 fixes for 5.13, take #1

- Fix regression with irqbypass not restarting the guest on failed connect
- Fix regression with debug register decoding resulting in overlapping access
- Commit exception state on exit to usrspace
- Fix the MMU notifier return values
- Add missing 'static' qualifiers in the new host stage-2 code
2021-05-17 09:55:12 +02:00
Linus Torvalds
ccb013c29d - Enable -Wundef for the compressed kernel build stage
- Reorganize SEV code to streamline and simplify future development
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Merge tag 'x86_urgent_for_v5.13_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Borislav Petkov:
 "The three SEV commits are not really urgent material. But we figured
  since getting them in now will avoid a huge amount of conflicts
  between future SEV changes touching tip, the kvm and probably other
  trees, sending them to you now would be best.

  The idea is that the tip, kvm etc branches for 5.14 will all base
  ontop of -rc2 and thus everything will be peachy. What is more, those
  changes are purely mechanical and defines movement so they should be
  fine to go now (famous last words).

  Summary:

   - Enable -Wundef for the compressed kernel build stage

   - Reorganize SEV code to streamline and simplify future development"

* tag 'x86_urgent_for_v5.13_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/boot/compressed: Enable -Wundef
  x86/msr: Rename MSR_K8_SYSCFG to MSR_AMD64_SYSCFG
  x86/sev: Move GHCB MSR protocol and NAE definitions in a common header
  x86/sev-es: Rename sev-es.{ch} to sev.{ch}
2021-05-16 09:31:06 -07:00
Linus Torvalds
0aa099a312 * Lots of bug fixes.
* Fix virtualization of RDPID
 
 * Virtualization of DR6_BUS_LOCK, which on bare metal is new in
   the 5.13 merge window
 
 * More nested virtualization migration fixes (nSVM and eVMCS)
 
 * Fix for KVM guest hibernation
 
 * Fix for warning in SEV-ES SRCU usage
 
 * Block KVM from loading on AMD machines with 5-level page tables,
   due to the APM not mentioning how host CR4.LA57 exactly impacts
   the guest.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:

 - Lots of bug fixes.

 - Fix virtualization of RDPID

 - Virtualization of DR6_BUS_LOCK, which on bare metal is new to this
   release

 - More nested virtualization migration fixes (nSVM and eVMCS)

 - Fix for KVM guest hibernation

 - Fix for warning in SEV-ES SRCU usage

 - Block KVM from loading on AMD machines with 5-level page tables, due
   to the APM not mentioning how host CR4.LA57 exactly impacts the
   guest.

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (48 commits)
  KVM: SVM: Move GHCB unmapping to fix RCU warning
  KVM: SVM: Invert user pointer casting in SEV {en,de}crypt helpers
  kvm: Cap halt polling at kvm->max_halt_poll_ns
  tools/kvm_stat: Fix documentation typo
  KVM: x86: Prevent deadlock against tk_core.seq
  KVM: x86: Cancel pvclock_gtod_work on module removal
  KVM: x86: Prevent KVM SVM from loading on kernels with 5-level paging
  KVM: X86: Expose bus lock debug exception to guest
  KVM: X86: Add support for the emulation of DR6_BUS_LOCK bit
  KVM: PPC: Book3S HV: Fix conversion to gfn-based MMU notifier callbacks
  KVM: x86: Hide RDTSCP and RDPID if MSR_TSC_AUX probing failed
  KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to guest CPU model
  KVM: x86: Move uret MSR slot management to common x86
  KVM: x86: Export the number of uret MSRs to vendor modules
  KVM: VMX: Disable loading of TSX_CTRL MSR the more conventional way
  KVM: VMX: Use common x86's uret MSR list as the one true list
  KVM: VMX: Use flag to indicate "active" uret MSRs instead of sorting list
  KVM: VMX: Configure list of user return MSRs at module init
  KVM: x86: Add support for RDPID without RDTSCP
  KVM: SVM: Probe and load MSR_TSC_AUX regardless of RDTSCP support in host
  ...
2021-05-10 12:30:45 -07:00
Brijesh Singh
059e5c321a x86/msr: Rename MSR_K8_SYSCFG to MSR_AMD64_SYSCFG
The SYSCFG MSR continued being updated beyond the K8 family; drop the K8
name from it.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lkml.kernel.org/r/20210427111636.1207-4-brijesh.singh@amd.com
2021-05-10 07:51:38 +02:00
Thomas Gleixner
3f804f6d20 KVM: x86: Prevent deadlock against tk_core.seq
syzbot reported a possible deadlock in pvclock_gtod_notify():

CPU 0  		  	   	    	    CPU 1
write_seqcount_begin(&tk_core.seq);
  pvclock_gtod_notify()			    spin_lock(&pool->lock);
    queue_work(..., &pvclock_gtod_work)	    ktime_get()
     spin_lock(&pool->lock);		      do {
     						seq = read_seqcount_begin(tk_core.seq)
						...
				              } while (read_seqcount_retry(&tk_core.seq, seq);

While this is unlikely to happen, it's possible.

Delegate queue_work() to irq_work() which postpones it until the
tk_core.seq write held region is left and interrupts are reenabled.

Fixes: 16e8d74d2da9 ("KVM: x86: notifier for clocksource changes")
Reported-by: syzbot+6beae4000559d41d80f8@syzkaller.appspotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Message-Id: <87h7jgm1zy.ffs@nanos.tec.linutronix.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:21 -04:00
Thomas Gleixner
594b27e677 KVM: x86: Cancel pvclock_gtod_work on module removal
Nothing prevents the following:

  pvclock_gtod_notify()
    queue_work(system_long_wq, &pvclock_gtod_work);
  ...
  remove_module(kvm);
  ...
  work_queue_run()
    pvclock_gtod_work()	<- UAF

Ditto for any other operation on that workqueue list head which touches
pvclock_gtod_work after module removal.

Cancel the work in kvm_arch_exit() to prevent that.

Fixes: 16e8d74d2da9 ("KVM: x86: notifier for clocksource changes")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Message-Id: <87czu4onry.ffs@nanos.tec.linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:21 -04:00
Chenyi Qiang
e8ea85fb28 KVM: X86: Add support for the emulation of DR6_BUS_LOCK bit
Bus lock debug exception introduces a new bit DR6_BUS_LOCK (bit 11 of
DR6) to indicate that bus lock #DB exception is generated. The set/clear
of DR6_BUS_LOCK is similar to the DR6_RTM. The processor clears
DR6_BUS_LOCK when the exception is generated. For all other #DB, the
processor sets this bit to 1. Software #DB handler should set this bit
before returning to the interrupted task.

In VMM, to avoid breaking the CPUs without bus lock #DB exception
support, activate the DR6_BUS_LOCK conditionally in DR6_FIXED_1 bits.
When intercepting the #DB exception caused by bus locks, bit 11 of the
exit qualification is set to identify it. The VMM should emulate the
exception by clearing the bit 11 of the guest DR6.

Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090433.13441-3-chenyi.qiang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:20 -04:00
Sean Christopherson
61a05d444d KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to guest CPU model
Squish the Intel and AMD emulation of MSR_TSC_AUX together and tie it to
the guest CPU model instead of the host CPU behavior.  While not strictly
necessary to avoid guest breakage, emulating cross-vendor "architecture"
will provide consistent behavior for the guest, e.g. WRMSR fault behavior
won't change if the vCPU is migrated to a host with divergent behavior.

Note, the "new" kvm_is_supported_user_return_msr() checks do not add new
functionality on either SVM or VMX.  On SVM, the equivalent was
"tsc_aux_uret_slot < 0", and on VMX the check was buried in the
vmx_find_uret_msr() call at the find_uret_msr label.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-15-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:19 -04:00
Sean Christopherson
e5fda4bbad KVM: x86: Move uret MSR slot management to common x86
Now that SVM and VMX both probe MSRs before "defining" user return slots
for them, consolidate the code for probe+define into common x86 and
eliminate the odd behavior of having the vendor code define the slot for
a given MSR.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:19 -04:00
Sean Christopherson
9cc39a5a43 KVM: x86: Export the number of uret MSRs to vendor modules
Split out and export the number of configured user return MSRs so that
VMX can iterate over the set of MSRs without having to do its own tracking.
Keep the list itself internal to x86 so that vendor code still has to go
through the "official" APIs to add/modify entries.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-13-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:18 -04:00
Sean Christopherson
8ea8b8d6f8 KVM: VMX: Use common x86's uret MSR list as the one true list
Drop VMX's global list of user return MSRs now that VMX doesn't resort said
list to isolate "active" MSRs, i.e. now that VMX's list and x86's list have
the same MSRs in the same order.

In addition to eliminating the redundant list, this will also allow moving
more of the list management into common x86.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:18 -04:00
Sean Christopherson
36fa06f9ff KVM: x86: Add support for RDPID without RDTSCP
Allow userspace to enable RDPID for a guest without also enabling RDTSCP.
Aside from checking for RDPID support in the obvious flows, VMX also needs
to set ENABLE_RDTSCP=1 when RDPID is exposed.

For the record, there is no known scenario where enabling RDPID without
RDTSCP is desirable.  But, both AMD and Intel architectures allow for the
condition, i.e. this is purely to make KVM more architecturally accurate.

Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
Cc: stable@vger.kernel.org
Reported-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:17 -04:00
Sean Christopherson
5104d7ffcf KVM: VMX: Disable preemption when probing user return MSRs
Disable preemption when probing a user return MSR via RDSMR/WRMSR.  If
the MSR holds a different value per logical CPU, the WRMSR could corrupt
the host's value if KVM is preempted between the RDMSR and WRMSR, and
then rescheduled on a different CPU.

Opportunistically land the helper in common x86, SVM will use the helper
in a future commit.

Fixes: 4be534102624 ("KVM: VMX: Initialize vmx->guest_msrs[] right after allocation")
Cc: stable@vger.kernel.org
Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-6-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:16 -04:00
Siddharth Chandrasekaran
aca352886e KVM: x86: Hoist input checks in kvm_add_msr_filter()
In ioctl KVM_X86_SET_MSR_FILTER, input from user space is validated
after a memdup_user(). For invalid inputs we'd memdup and then call
kfree unnecessarily. Hoist input validation to avoid kfree altogether.

Signed-off-by: Siddharth Chandrasekaran <sidcha@amazon.de>
Message-Id: <20210503122111.13775-1-sidcha@amazon.de>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:14 -04:00
Wanpeng Li
1604571401 KVM: x86: Defer vtime accounting 'til after IRQ handling
Defer the call to account guest time until after servicing any IRQ(s)
that happened in the guest or immediately after VM-Exit.  Tick-based
accounting of vCPU time relies on PF_VCPU being set when the tick IRQ
handler runs, and IRQs are blocked throughout the main sequence of
vcpu_enter_guest(), including the call into vendor code to actually
enter and exit the guest.

This fixes a bug where reported guest time remains '0', even when
running an infinite loop in the guest:

  https://bugzilla.kernel.org/show_bug.cgi?id=209831

Fixes: 87fa7f3e98a131 ("x86/kvm: Move context tracking where it belongs")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210505002735.1684165-4-seanjc@google.com
2021-05-05 22:54:11 +02:00