On 3/17/25 00:23, Nikunj A Dadhania wrote:
> From: Ketan Chaturvedi <Ketan.Chaturvedi@xxxxxxx>
>
> 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.
>
> As the frequency needs to be set in the SNP_LAUNCH_START command, userspace
> should set the frequency using the KVM_CAP_SET_TSC_KHZ VM ioctl instead of
> the VCPU ioctl. The desired_tsc_khz defaults to kvm->arch.default_tsc_khz.
>
> Signed-off-by: Ketan Chaturvedi <Ketan.Chaturvedi@xxxxxxx>
> Co-developed-by: Nikunj A Dadhania <nikunj@xxxxxxx>
> Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
Just one minor comment below, that can be ignored unless you have to do
another version.
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> arch/x86/include/uapi/asm/kvm.h | 3 ++-
> arch/x86/kvm/svm/sev.c | 14 ++++++++++++++
> 2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 9e75da97bce0..87ed9f77314d 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -836,7 +836,8 @@ struct kvm_sev_snp_launch_start {
> __u64 policy;
> __u8 gosvw[16];
> __u16 flags;
> - __u8 pad0[6];
> + __u8 pad0[2];
> + __u32 desired_tsc_khz;
> __u64 pad1[4];
> };
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 80a80929e6a3..4ee8d233f61f 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2226,6 +2226,14 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>
> start.gctx_paddr = __psp_pa(sev->snp_context);
> start.policy = params.policy;
> +
> + if (snp_secure_tsc_enabled(kvm)) {
> + if (!kvm->arch.default_tsc_khz)
> + return -EINVAL;
> +
> + start.desired_tsc_khz = kvm->arch.default_tsc_khz;
> + }
> +
> memcpy(start.gosvw, params.gosvw, sizeof(params.gosvw));
> rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_START, &start, &argp->error);
> if (rc) {
> @@ -2467,6 +2475,9 @@ static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
> }
>
> svm->vcpu.arch.guest_state_protected = true;
> + if (snp_secure_tsc_enabled(kvm))
> + svm->vcpu.arch.guest_tsc_protected = true;
> +
This could just be:
vcpu->arch.guest_tsc_protected = snp_secure_tsc_enabled(kvm);
(and you could clean up the line above to:
vcpu->arch.guest_state_protected = true;
while you're at it.)
Thanks,
Tom
> /*
> * SEV-ES (and thus SNP) guest mandates LBR Virtualization to
> * be _always_ ON. Enable it only after setting
> @@ -3079,6 +3090,9 @@ void __init sev_hardware_setup(void)
> sev_supported_vmsa_features = 0;
> if (sev_es_debug_swap_enabled)
> sev_supported_vmsa_features |= SVM_SEV_FEAT_DEBUG_SWAP;
> +
> + if (sev_snp_enabled && cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC))
> + sev_supported_vmsa_features |= SVM_SEV_FEAT_SECURE_TSC;
> }
>
> void sev_hardware_unsetup(void)
