[PATCH v6 0/4] Enable Secure TSC for SEV-SNP

[Nikunj A Dadhania <nikunj@amd.com>]

The hypervisor controls TSC value calculations for the guest. A malicious
hypervisor can prevent the guest from progressing. The Secure TSC feature for
SEV-SNP allows guests to securely use the RDTSC and RDTSCP instructions. This
ensures the guest has a consistent view of time and prevents a malicious
hypervisor from manipulating time, such as making it appear to move backward or
advance too quickly. For more details, refer to the "Secure Nested Paging
(SEV-SNP)" section, subsection "Secure TSC" in APM Volume 2.

This patch set is also available at:

  https://github.com/AMDESE/linux-kvm/tree/sectsc-host-latest

and is based on kvm/master

Testing Secure TSC
-----------------

Secure TSC guest patches are available as part of v6.14-rc1.

QEMU changes:
https://github.com/nikunjad/qemu/tree/snp-securetsc-latest

QEMU command line SEV-SNP with Secure TSC:

  qemu-system-x86_64 -cpu EPYC-Milan-v2 -smp 4 \
    -object memory-backend-memfd,id=ram1,size=1G,share=true,prealloc=false,reserve=false \
    -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,secure-tsc=on,stsc-freq=2000000000 \
    -machine q35,confidential-guest-support=sev0,memory-backend=ram1 \
    ...

Changelog:
----------
v6:
* Rebased on top of kvm/master
* Collected Reviewed-by/Tested-by
* s/svm->vcpu/vcpu/ in snp_launch_update_vmsa() as vcpu pointer is already available (Tom)
* Simplify assignment of guest_protected_tsc (Tom)


v5: https://lore.kernel.org/kvm/20250317052308.498244-1-nikunj@amd.com/
* Rebased on top of kvm/queue that includes protected TSC patches
  https://lore.kernel.org/kvm/20250314183422.2990277-1-pbonzini@redhat.com/
* Dropped patch 4/5 as it is not required after protected TSC patches
* Set guest_tsc_protected when Secure TSC is enabled (Paolo)
* Collect Reviewed-by from Tom
* Base the desired_tsc_freq on KVM's ABI (Sean)

Ketan Chaturvedi (1):
  KVM: SVM: Enable Secure TSC for SNP guests

Nikunj A Dadhania (3):
  x86/cpufeatures: Add SNP Secure TSC
  KVM: SVM: Add missing member in SNP_LAUNCH_START command structure
  KVM: SVM: Add GUEST_TSC_FREQ MSR for Secure TSC enabled guests

 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/include/asm/svm.h         |  1 +
 arch/x86/include/uapi/asm/kvm.h    |  3 ++-
 arch/x86/kvm/svm/sev.c             | 18 +++++++++++++++++-
 arch/x86/kvm/svm/svm.c             |  1 +
 arch/x86/kvm/svm/svm.h             | 11 ++++++++++-
 include/linux/psp-sev.h            |  2 ++
 7 files changed, 34 insertions(+), 3 deletions(-)


base-commit: c77eee50caa289fee6cfde146471aa7b0f311471
-- 
2.43.0