KVM: SVM: Enable Secure TSC for SNP guests

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Add support for Secure TSC, allowing userspace to configure the Secure TSC
feature for SNP guests. Use the SNP specification's desired TSC frequency
parameter during the SNP_LAUNCH_START command to set the mean TSC
frequency in KHz for Secure TSC enabled guests.

Always use kvm->arch.arch.default_tsc_khz as the TSC frequency that is
passed to SNP guests in the SNP_LAUNCH_START command.  The default value
is the host TSC frequency.  The userspace can optionally change the TSC
frequency via the KVM_SET_TSC_KHZ ioctl before calling the
SNP_LAUNCH_START ioctl.

Introduce the read-only MSR GUEST_TSC_FREQ (0xc0010134) that returns
guest's effective frequency in MHZ when Secure TSC is enabled for SNP
guests. Disable interception of this MSR when Secure TSC is enabled. Note
that GUEST_TSC_FREQ MSR is accessible only to the guest and not from the
hypervisor context.

Co-developed-by: Ketan Chaturvedi <Ketan.Chaturvedi@amd.com>
Signed-off-by: Ketan Chaturvedi <Ketan.Chaturvedi@amd.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
[sean: contain Secure TSC to sev.c]
Link: https://lore.kernel.org/r/20250819234833.3080255-9-seanjc@google.com
[sean: return -EINVAL if TSC frequency is '0']
Signed-off-by: Sean Christopherson <seanjc@google.com>

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Nikunj A Dadhania 2025-08-19 16:48:33 -07:00 • committed by Sean Christopherson

parent f7b1f0c162

commit a311fce2b6

2 changed files with 29 additions and 0 deletions

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arch/x86/include/asm/svm.h

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28

arch/x86/kvm/svm/sev.c

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