| Message ID | 20250408093213.57962-1-nikunj@amd.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Enable Secure TSC for SEV-SNP | expand |
On 4/8/2025 3:02 PM, Nikunj A Dadhania wrote: > 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) A gentle reminder, any other suggestions/improvement ? Regards Nikunj
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