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During patch review, it was decided the SNP guest driver name should not
be SEV-SNP specific, but should be generic for use with anything SEV.
However, this feedback was missed and the driver name, and many of the
driver functions and structures, are SEV-SNP name specific. Rename the
driver to "sev-guest" (to match the misc device that is created) and
update some of the function and structure names, too.
While in the file, adjust the one pr_err() message to be a dev_err()
message so that the message, if issued, uses the driver name.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/307710bb5515c9088a19fd0b930268c7300479b2.1650464054.git.thomas.lendacky@amd.com
The helpers in arch/x86/boot/compressed/efi.c might be used during
early boot to access the EFI system/config tables, and in some cases
these EFI helpers might attempt to print debug/error messages, before
console_init() has been called.
__putstr() checks some variables to avoid printing anything before
the console has been initialized, but this isn't enough since those
variables live in .bss, which may not have been cleared yet. This can
lead to a triple-fault occurring, primarily when booting in legacy/CSM
mode (where EFI helpers will attempt to print some debug messages).
Fix this by declaring these globals in .data section instead so there
is no dependency on .bss being cleared before accessing them.
Fixes: c01fce9cef849 ("x86/compressed: Add SEV-SNP feature detection/setup")
Reported-by: Borislav Petkov <bp@suse.de>
Suggested-by: Thomas Lendacky <Thomas.Lendacky@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220420152613.145077-1-michael.roth@amd.com
Replace the halt loop in handle_vc_boot_ghcb() with an
sev_es_terminate(). The HLT gives the system no indication the guest is
unhappy. The termination request will signal there was an error during
VC handling during boot.
[ bp: Update it to pass the reason set too. ]
Signed-off-by: Peter Gonda <pgonda@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20220317211913.1397427-1-pgonda@google.com
Update the documentation with information regarding SEV-SNP CPUID
Enforcement details and what sort of assurances it provides to guests.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-47-brijesh.singh@amd.com
Version 2 of GHCB specification defines Non-Automatic-Exit (NAE) to get
extended guest report which is similar to the SNP_GET_REPORT ioctl. The
main difference is related to the additional data that will be returned.
That additional data returned is a certificate blob that can be used by
the SNP guest user. The certificate blob layout is defined in the GHCB
specification. The driver simply treats the blob as a opaque data and
copies it to userspace.
[ bp: Massage commit message, cast 1st arg of access_ok() ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-46-brijesh.singh@amd.com
The SNP_GET_DERIVED_KEY ioctl interface can be used by the SNP guest to
ask the firmware to provide a key derived from a root key. The derived
key may be used by the guest for any purposes it chooses, such as a
sealing key or communicating with the external entities.
See SEV-SNP firmware spec for more information.
[ bp: No need to memset "req" - it will get overwritten. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-45-brijesh.singh@amd.com
The SEV-SNP specification provides the guest a mechanism to communicate
with the PSP without risk from a malicious hypervisor who wishes to
read, alter, drop or replay the messages sent. The driver uses
snp_issue_guest_request() to issue GHCB SNP_GUEST_REQUEST or
SNP_EXT_GUEST_REQUEST NAE events to submit the request to PSP.
The PSP requires that all communication should be encrypted using key
specified through a struct snp_guest_platform_data descriptor.
Userspace can use SNP_GET_REPORT ioctl() to query the guest attestation
report.
See SEV-SNP spec section Guest Messages for more details.
[ bp: Remove the "what" from the commit message, massage. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-44-brijesh.singh@amd.com
Version 2 of the GHCB specification provides a Non Automatic Exit (NAE)
event type that can be used by the SEV-SNP guest to communicate with the
PSP without risk from a malicious hypervisor who wishes to read, alter,
drop or replay the messages sent.
SNP_LAUNCH_UPDATE can insert two special pages into the guest’s memory:
the secrets page and the CPUID page. The PSP firmware populates the
contents of the secrets page. The secrets page contains encryption keys
used by the guest to interact with the firmware. Because the secrets
page is encrypted with the guest’s memory encryption key, the hypervisor
cannot read the keys. See SEV-SNP firmware spec for further details on
the secrets page format.
Create a platform device that the SEV-SNP guest driver can bind to get
the platform resources such as encryption key and message id to use to
communicate with the PSP. The SEV-SNP guest driver provides a userspace
interface to get the attestation report, key derivation, extended
attestation report etc.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-43-brijesh.singh@amd.com
Version 2 of GHCB specification provides SNP_GUEST_REQUEST and
SNP_EXT_GUEST_REQUEST NAE that can be used by the SNP guest to
communicate with the PSP.
While at it, add a snp_issue_guest_request() helper that will be used by
driver or other subsystem to issue the request to PSP.
See SEV-SNP firmware and GHCB spec for more details.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-42-brijesh.singh@amd.com
For debugging purposes it is very useful to have a way to see the full
contents of the SNP CPUID table provided to a guest. Add an sev=debug
kernel command-line option to do so.
Also introduce some infrastructure so that additional options can be
specified via sev=option1[,option2] over time in a consistent manner.
[ bp: Massage, simplify string parsing. ]
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-41-brijesh.singh@amd.com
SEV-SNP guests will be provided the location of special 'secrets' and
'CPUID' pages via the Confidential Computing blob. This blob is
provided to the run-time kernel either through a boot_params field that
was initialized by the boot/compressed kernel, or via a setup_data
structure as defined by the Linux Boot Protocol.
Locate the Confidential Computing blob from these sources and, if found,
use the provided CPUID page/table address to create a copy that the
run-time kernel will use when servicing CPUID instructions via a #VC
handler.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-40-brijesh.singh@amd.com
Initial/preliminary detection of SEV-SNP is done via the Confidential
Computing blob. Check for it prior to the normal SEV/SME feature
initialization, and add some sanity checks to confirm it agrees with
SEV-SNP CPUID/MSR bits.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-39-brijesh.singh@amd.com
The run-time kernel will need to access the Confidential Computing blob
very early during boot to access the CPUID table it points to. At that
stage, it will be relying on the identity-mapped page table set up by
the boot/compressed kernel, so make sure the blob and the CPUID table it
points to are mapped in advance.
[ bp: Massage. ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-38-brijesh.singh@amd.com
SEV-specific code will need to add some additional mappings, but doing
this within ident_map_64.c requires some SEV-specific helpers to be
exported and some SEV-specific struct definitions to be pulled into
ident_map_64.c. Instead, export add_identity_map() so SEV-specific (and
other subsystem-specific) code can be better contained outside of
ident_map_64.c.
While at it, rename the function to kernel_add_identity_map(), similar
to the kernel_ident_mapping_init() function it relies upon.
No functional changes.
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-37-brijesh.singh@amd.com
SEV-SNP guests will be provided the location of special 'secrets'
'CPUID' pages via the Confidential Computing blob. This blob is
provided to the boot kernel either through an EFI config table entry,
or via a setup_data structure as defined by the Linux Boot Protocol.
Locate the Confidential Computing from these sources and, if found,
use the provided CPUID page/table address to create a copy that the
boot kernel will use when servicing CPUID instructions via a #VC CPUID
handler.
[ bp: s/cpuid/CPUID/ ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-36-brijesh.singh@amd.com
Initial/preliminary detection of SEV-SNP is done via the Confidential
Computing blob. Check for it prior to the normal SEV/SME feature
initialization, and add some sanity checks to confirm it agrees with
SEV-SNP CPUID/MSR bits.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-35-brijesh.singh@amd.com
The previously defined Confidential Computing blob is provided to the
kernel via a setup_data structure or EFI config table entry. Currently,
these are both checked for by boot/compressed kernel to access the CPUID
table address within it for use with SEV-SNP CPUID enforcement.
To also enable that enforcement for the run-time kernel, similar
access to the CPUID table is needed early on while it's still using
the identity-mapped page table set up by boot/compressed, where global
pointers need to be accessed via fixup_pointer().
This isn't much of an issue for accessing setup_data, and the EFI config
table helper code currently used in boot/compressed *could* be used in
this case as well since they both rely on identity-mapping. However, it
has some reliance on EFI helpers/string constants that would need to be
accessed via fixup_pointer(), and fixing it up while making it shareable
between boot/compressed and run-time kernel is fragile and introduces a
good bit of ugliness.
Instead, add a boot_params->cc_blob_address pointer that the
boot/compressed kernel can initialize so that the run-time kernel can
access the CC blob from there instead of re-scanning the EFI config
table.
Also document these in Documentation/x86/zero-page.rst. While there,
add missing documentation for the acpi_rsdp_addr field, which serves a
similar purpose in providing the run-time kernel a pointer to the ACPI
RSDP table so that it does not need to [re-]scan the EFI configuration
table.
[ bp: Fix typos, massage commit message. ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-34-brijesh.singh@amd.com
CPUID instructions generate a #VC exception for SEV-ES/SEV-SNP guests,
for which early handlers are currently set up to handle. In the case
of SEV-SNP, guests can use a configurable location in guest memory
that has been pre-populated with a firmware-validated CPUID table to
look up the relevant CPUID values rather than requesting them from
hypervisor via a VMGEXIT. Add the various hooks in the #VC handlers to
allow CPUID instructions to be handled via the table. The code to
actually configure/enable the table will be added in a subsequent
commit.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-33-brijesh.singh@amd.com
This code will also be used later for SEV-SNP-validated CPUID code in
some cases, so move it to a common helper.
While here, also add a check to terminate in cases where the CPUID
function/subfunction is indexed and the subfunction is non-zero, since
the GHCB MSR protocol does not support non-zero subfunctions.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-32-brijesh.singh@amd.com
Determining which CPUID leafs have significant ECX/index values is
also needed by guest kernel code when doing SEV-SNP-validated CPUID
lookups. Move this to common code to keep future updates in sync.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-31-brijesh.singh@amd.com
While launching encrypted guests, the hypervisor may need to provide
some additional information during the guest boot. When booting under an
EFI-based BIOS, the EFI configuration table contains an entry for the
confidential computing blob that contains the required information.
To support booting encrypted guests on non-EFI VMs, the hypervisor
needs to pass this additional information to the guest kernel using a
different method.
For this purpose, introduce SETUP_CC_BLOB type in setup_data to hold
the physical address of the confidential computing blob location. The
boot loader or hypervisor may choose to use this method instead of an
EFI configuration table. The CC blob location scanning should give
preference to a setup_data blob over an EFI configuration table.
In AMD SEV-SNP, the CC blob contains the address of the secrets and
CPUID pages. The secrets page includes information such as a VM to PSP
communication key and the CPUID page contains PSP-filtered CPUID values.
Define the AMD SEV confidential computing blob structure.
While at it, define the EFI GUID for the confidential computing blob.
[ bp: Massage commit message, mark struct __packed. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220307213356.2797205-30-brijesh.singh@amd.com
Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related code
into a set of helpers that can be re-used for that purpose.
In this instance, the current acpi.c kexec handling is mainly used to
get the alternative EFI config table address provided by kexec via a
setup_data entry of type SETUP_EFI. If not present, the code then falls
back to normal EFI config table address provided by EFI system table.
This would need to be done by all call-sites attempting to access the
EFI config table, so just have efi_get_conf_table() handle that
automatically.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-29-brijesh.singh@amd.com
Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related code
into a set of helpers that can be re-used for that purpose.
[ bp: Unbreak unnecessarily broken lines. ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-28-brijesh.singh@amd.com
Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related code
into a set of helpers that can be re-used for that purpose.
[ bp: Remove superfluous zeroing of a stack variable. ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-27-brijesh.singh@amd.com
Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related
code into a set of helpers that can be re-used for that purpose.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-26-brijesh.singh@amd.com
Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related code
into a set of helpers that can be re-used for that purpose.
First, carve out the functionality which determines the EFI environment
type the machine is booting on.
[ bp: Massage commit message. ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-25-brijesh.singh@amd.com
Due to
103a4908ad4d ("x86/head/64: Disable stack protection for head$(BITS).o")
kernel/head{32,64}.c are compiled with -fno-stack-protector to allow
a call to set_bringup_idt_handler(), which would otherwise have stack
protection enabled with CONFIG_STACKPROTECTOR_STRONG.
While sufficient for that case, there may still be issues with calls to
any external functions that were compiled with stack protection enabled
that in-turn make stack-protected calls, or if the exception handlers
set up by set_bringup_idt_handler() make calls to stack-protected
functions.
Subsequent patches for SEV-SNP CPUID validation support will introduce
both such cases. Attempting to disable stack protection for everything
in scope to address that is prohibitive since much of the code, like the
SEV-ES #VC handler, is shared code that remains in use after boot and
could benefit from having stack protection enabled. Attempting to inline
calls is brittle and can quickly balloon out to library/helper code
where that's not really an option.
Instead, re-enable stack protection for head32.c/head64.c, and make the
appropriate changes to ensure the segment used for the stack canary is
initialized in advance of any stack-protected C calls.
For head64.c:
- The BSP will enter from startup_64() and call into C code
(startup_64_setup_env()) shortly after setting up the stack, which
may result in calls to stack-protected code. Set up %gs early to allow
for this safely.
- APs will enter from secondary_startup_64*(), and %gs will be set up
soon after. There is one call to C code prior to %gs being setup
(__startup_secondary_64()), but it is only to fetch 'sme_me_mask'
global, so just load 'sme_me_mask' directly instead, and remove the
now-unused __startup_secondary_64() function.
For head32.c:
- BSPs/APs will set %fs to __BOOT_DS prior to any C calls. In recent
kernels, the compiler is configured to access the stack canary at
%fs:__stack_chk_guard [1], which overlaps with the initial per-cpu
'__stack_chk_guard' variable in the initial/"master" .data..percpu
area. This is sufficient to allow access to the canary for use
during initial startup, so no changes are needed there.
[1] 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable")
[ bp: Massage commit message. ]
Suggested-by: Joerg Roedel <jroedel@suse.de> #for 64-bit %gs set up
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-24-brijesh.singh@amd.com
To provide a more secure way to start APs under SEV-SNP, use the SEV-SNP
AP Creation NAE event. This allows for guest control over the AP register
state rather than trusting the hypervisor with the SEV-ES Jump Table
address.
During native_smp_prepare_cpus(), invoke an SEV-SNP function that, if
SEV-SNP is active, will set/override apic->wakeup_secondary_cpu. This
will allow the SEV-SNP AP Creation NAE event method to be used to boot
the APs. As a result of installing the override when SEV-SNP is active,
this method of starting the APs becomes the required method. The override
function will fail to start the AP if the hypervisor does not have
support for AP creation.
[ bp: Work in forgotten review comments. ]
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-23-brijesh.singh@amd.com
Add the needed functionality to change pages state from shared
to private and vice-versa using the Page State Change VMGEXIT as
documented in the GHCB spec.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-22-brijesh.singh@amd.com
probe_roms() accesses the memory range (0xc0000 - 0x10000) to probe
various ROMs. The memory range is not part of the E820 system RAM range.
The memory range is mapped as private (i.e encrypted) in the page table.
When SEV-SNP is active, all the private memory must be validated before
accessing. The ROM range was not part of E820 map, so the guest BIOS
did not validate it. An access to invalidated memory will cause a
exception yet, so validate the ROM memory regions before it is accessed.
[ bp: Massage commit message. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-21-brijesh.singh@amd.com
The encryption attribute for the .bss..decrypted section is cleared in the
initial page table build. This is because the section contains the data
that need to be shared between the guest and the hypervisor.
When SEV-SNP is active, just clearing the encryption attribute in the
page table is not enough. The page state needs to be updated in the RMP
table.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-20-brijesh.singh@amd.com
early_set_memory_{encrypted,decrypted}() are used for changing the page
state from decrypted (shared) to encrypted (private) and vice versa.
When SEV-SNP is active, the page state transition needs to go through
additional steps.
If the page is transitioned from shared to private, then perform the
following after the encryption attribute is set in the page table:
1. Issue the page state change VMGEXIT to add the page as a private
in the RMP table.
2. Validate the page after its successfully added in the RMP table.
To maintain the security guarantees, if the page is transitioned from
private to shared, then perform the following before clearing the
encryption attribute from the page table.
1. Invalidate the page.
2. Issue the page state change VMGEXIT to make the page shared in the
RMP table.
early_set_memory_{encrypted,decrypted}() can be called before the GHCB
is setup so use the SNP page state MSR protocol VMGEXIT defined in the
GHCB specification to request the page state change in the RMP table.
While at it, add a helper snp_prep_memory() which will be used in
probe_roms(), in a later patch.
[ bp: Massage commit message. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-19-brijesh.singh@amd.com
The SEV-SNP guest is required by the GHCB spec to register the GHCB's
Guest Physical Address (GPA). This is because the hypervisor may prefer
that a guest uses a consistent and/or specific GPA for the GHCB associated
with a vCPU. For more information, see the GHCB specification section
"GHCB GPA Registration".
[ bp: Cleanup comments. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-18-brijesh.singh@amd.com
The SEV-SNP guest is required by the GHCB spec to register the GHCB's
Guest Physical Address (GPA). This is because the hypervisor may prefer
that a guest use a consistent and/or specific GPA for the GHCB associated
with a vCPU. For more information, see the GHCB specification section
"GHCB GPA Registration".
If hypervisor can not work with the guest provided GPA then terminate the
guest boot.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-17-brijesh.singh@amd.com
Many of the integrity guarantees of SEV-SNP are enforced through the
Reverse Map Table (RMP). Each RMP entry contains the GPA at which a
particular page of DRAM should be mapped. The VMs can request the
hypervisor to add pages in the RMP table via the Page State Change
VMGEXIT defined in the GHCB specification.
Inside each RMP entry is a Validated flag; this flag is automatically
cleared to 0 by the CPU hardware when a new RMP entry is created for a
guest. Each VM page can be either validated or invalidated, as indicated
by the Validated flag in the RMP entry. Memory access to a private page
that is not validated generates a #VC. A VM must use the PVALIDATE
instruction to validate a private page before using it.
To maintain the security guarantee of SEV-SNP guests, when transitioning
pages from private to shared, the guest must invalidate the pages before
asking the hypervisor to change the page state to shared in the RMP table.
After the pages are mapped private in the page table, the guest must
issue a page state change VMGEXIT to mark the pages private in the RMP
table and validate them.
Upon boot, BIOS should have validated the entire system memory.
During the kernel decompression stage, early_setup_ghcb() uses
set_page_decrypted() to make the GHCB page shared (i.e. clear encryption
attribute). And while exiting from the decompression, it calls
set_page_encrypted() to make the page private.
Add snp_set_page_{private,shared}() helpers that are used by
set_page_{decrypted,encrypted}() to change the page state in the RMP
table.
[ bp: Massage commit message and comments. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-16-brijesh.singh@amd.com
The Virtual Machine Privilege Level (VMPL) feature in the SEV-SNP
architecture allows a guest VM to divide its address space into four
levels. The level can be used to provide hardware isolated abstraction
layers within a VM. VMPL0 is the highest privilege level, and VMPL3 is
the least privilege level. Certain operations must be done by the VMPL0
software, such as:
* Validate or invalidate memory range (PVALIDATE instruction)
* Allocate VMSA page (RMPADJUST instruction when VMSA=1)
The initial SNP support requires that the guest kernel is running at
VMPL0. Add such a check to verify the guest is running at level 0 before
continuing the boot. There is no easy method to query the current VMPL
level, so use the RMPADJUST instruction to determine whether the guest
is running at the VMPL0.
[ bp: Massage commit message. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-15-brijesh.singh@amd.com
An SNP-active guest uses the PVALIDATE instruction to validate or
rescind the validation of a guest page’s RMP entry. Upon completion, a
return code is stored in EAX and rFLAGS bits are set based on the return
code. If the instruction completed successfully, the carry flag (CF)
indicates if the content of the RMP were changed or not.
See AMD APM Volume 3 for additional details.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-14-brijesh.singh@amd.com
Version 2 of the GHCB specification added the advertisement of features
that are supported by the hypervisor. If the hypervisor supports SEV-SNP
then it must set the SEV-SNP features bit to indicate that the base
functionality is supported.
Check that feature bit while establishing the GHCB; if failed, terminate
the guest.
Version 2 of the GHCB specification adds several new Non-Automatic Exits
(NAEs), most of them are optional except the hypervisor feature. Now
that the hypervisor feature NAE is implemented, bump the GHCB maximum
supported protocol version.
While at it, move the GHCB protocol negotiation check from the #VC
exception handler to sev_enable() so that all feature detection happens
before the first #VC exception.
While at it, document why the GHCB page cannot be setup from
load_stage2_idt().
[ bp: Massage commit message. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-13-brijesh.singh@amd.com
The SEV-ES guest calls sev_es_negotiate_protocol() to negotiate the GHCB
protocol version before establishing the GHCB. Cache the negotiated GHCB
version so that it can be used later.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-12-brijesh.singh@amd.com
The GHCB specification defines the reason code for reason set 0. The
reason codes defined in the set 0 do not cover all possible causes for a
guest to request termination.
The reason sets 1 to 255 are reserved for the vendor-specific codes.
Reserve the reason set 1 for the Linux guest. Define the error codes for
reason set 1 so that one can have meaningful termination reasons and thus
better guest failure diagnosis.
While at it, change sev_es_terminate() to accept a reason set parameter.
[ bp: Massage commit message. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-11-brijesh.singh@amd.com
The CC_ATTR_GUEST_SEV_SNP can be used by the guest to query whether the
SNP (Secure Nested Paging) feature is active.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-10-brijesh.singh@amd.com
sme_enable() handles feature detection for both SEV and SME. Future
patches will also use it for SEV-SNP feature detection/setup, which
will need to be done immediately after the first #VC handler is set up.
Move it now in preparation.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-9-brijesh.singh@amd.com
With upcoming SEV-SNP support, SEV-related features need to be
initialized earlier during boot, at the same point the initial #VC
handler is set up, so that the SEV-SNP CPUID table can be utilized
during the initial feature checks. Also, SEV-SNP feature detection
will rely on EFI helper functions to scan the EFI config table for the
Confidential Computing blob, and so would need to be implemented at
least partially in C.
Currently set_sev_encryption_mask() is used to initialize the
sev_status and sme_me_mask globals that advertise what SEV/SME features
are available in a guest. Rename it to sev_enable() to better reflect
that (SME is only enabled in the case of SEV guests in the
boot/compressed kernel), and move it to just after the stage1 #VC
handler is set up so that it can be used to initialize SEV-SNP as well
in future patches.
While at it, re-implement it as C code so that all SEV feature
detection can be better consolidated with upcoming SEV-SNP feature
detection, which will also be in C.
The 32-bit entry path remains unchanged, as it never relied on the
set_sev_encryption_mask() initialization to begin with.
[ bp: Massage commit message. ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-8-brijesh.singh@amd.com
Update all C code to use the new boot_rdmsr()/boot_wrmsr() helpers
instead of relying on inline assembly.
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-7-brijesh.singh@amd.com
The current set of helpers used throughout the run-time kernel have
dependencies on code/facilities outside of the boot kernel, so there
are a number of call-sites throughout the boot kernel where inline
assembly is used instead. More will be added with subsequent patches
that add support for SEV-SNP, so take the opportunity to provide a basic
set of helpers that can be used by the boot kernel to reduce reliance on
inline assembly.
Use boot_* prefix so that it's clear these are helpers specific to the
boot kernel to avoid any confusion with the various other MSR read/write
helpers.
[ bp: Disambiguate parameter names and trim comment. ]
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-6-brijesh.singh@amd.com
This is the final step in defining the multiple save areas to keep them
separate and ensuring proper operation amongst the different types of
guests. Update the SEV-ES/SEV-SNP save area to match the APM. This save
area will be used for the upcoming SEV-SNP AP Creation NAE event support.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-5-brijesh.singh@amd.com
