0dbb112304
This hypercall is used by the SEV guest to notify a change in the page encryption status to the hypervisor. The hypercall should be invoked only when the encryption attribute is changed from encrypted -> decrypted and vice versa. By default all guest pages are considered encrypted. The hypercall exits to userspace to manage the guest shared regions and integrate with the userspace VMM's migration code. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Borislav Petkov <bp@suse.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: x86@kernel.org Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Steve Rutherford <srutherford@google.com> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> Co-developed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Co-developed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <90778988e1ee01926ff9cac447aacb745f954c8c.1623174621.git.ashish.kalra@amd.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
125 lines
5.3 KiB
ReStructuredText
125 lines
5.3 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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==============
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KVM CPUID bits
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==============
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:Author: Glauber Costa <glommer@gmail.com>
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A guest running on a kvm host, can check some of its features using
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cpuid. This is not always guaranteed to work, since userspace can
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mask-out some, or even all KVM-related cpuid features before launching
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a guest.
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KVM cpuid functions are:
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function: KVM_CPUID_SIGNATURE (0x40000000)
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returns::
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eax = 0x40000001
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ebx = 0x4b4d564b
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ecx = 0x564b4d56
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edx = 0x4d
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Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM".
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The value in eax corresponds to the maximum cpuid function present in this leaf,
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and will be updated if more functions are added in the future.
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Note also that old hosts set eax value to 0x0. This should
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be interpreted as if the value was 0x40000001.
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This function queries the presence of KVM cpuid leafs.
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function: define KVM_CPUID_FEATURES (0x40000001)
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returns::
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ebx, ecx
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eax = an OR'ed group of (1 << flag)
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where ``flag`` is defined as below:
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================================== =========== ================================
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flag value meaning
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================================== =========== ================================
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KVM_FEATURE_CLOCKSOURCE 0 kvmclock available at msrs
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0x11 and 0x12
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KVM_FEATURE_NOP_IO_DELAY 1 not necessary to perform delays
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on PIO operations
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KVM_FEATURE_MMU_OP 2 deprecated
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KVM_FEATURE_CLOCKSOURCE2 3 kvmclock available at msrs
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0x4b564d00 and 0x4b564d01
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KVM_FEATURE_ASYNC_PF 4 async pf can be enabled by
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writing to msr 0x4b564d02
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KVM_FEATURE_STEAL_TIME 5 steal time can be enabled by
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writing to msr 0x4b564d03
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KVM_FEATURE_PV_EOI 6 paravirtualized end of interrupt
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handler can be enabled by
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writing to msr 0x4b564d04
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KVM_FEATURE_PV_UNHALT 7 guest checks this feature bit
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before enabling paravirtualized
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spinlock support
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KVM_FEATURE_PV_TLB_FLUSH 9 guest checks this feature bit
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before enabling paravirtualized
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tlb flush
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KVM_FEATURE_ASYNC_PF_VMEXIT 10 paravirtualized async PF VM EXIT
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can be enabled by setting bit 2
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when writing to msr 0x4b564d02
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KVM_FEATURE_PV_SEND_IPI 11 guest checks this feature bit
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before enabling paravirtualized
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send IPIs
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KVM_FEATURE_POLL_CONTROL 12 host-side polling on HLT can
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be disabled by writing
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to msr 0x4b564d05.
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KVM_FEATURE_PV_SCHED_YIELD 13 guest checks this feature bit
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before using paravirtualized
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sched yield.
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KVM_FEATURE_ASYNC_PF_INT 14 guest checks this feature bit
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before using the second async
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pf control msr 0x4b564d06 and
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async pf acknowledgment msr
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0x4b564d07.
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KVM_FEATURE_MSI_EXT_DEST_ID 15 guest checks this feature bit
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before using extended destination
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ID bits in MSI address bits 11-5.
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KVM_FEATURE_HC_MAP_GPA_RANGE 16 guest checks this feature bit before
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using the map gpa range hypercall
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to notify the page state change
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KVM_FEATURE_MIGRATION_CONTROL 17 guest checks this feature bit before
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using MSR_KVM_MIGRATION_CONTROL
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KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24 host will warn if no guest-side
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per-cpu warps are expected in
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kvmclock
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================================== =========== ================================
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::
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edx = an OR'ed group of (1 << flag)
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Where ``flag`` here is defined as below:
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================== ============ =================================
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flag value meaning
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================== ============ =================================
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KVM_HINTS_REALTIME 0 guest checks this feature bit to
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determine that vCPUs are never
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preempted for an unlimited time
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allowing optimizations
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================== ============ =================================
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