diff mbox series

[v5,4/4] KVM: SVM: Enable Secure TSC for SNP guests

Message ID 20250317052308.498244-5-nikunj@amd.com (mailing list archive)
State New
Headers show
Series Enable Secure TSC for SEV-SNP | expand

Commit Message

Nikunj A Dadhania March 17, 2025, 5:23 a.m. UTC
From: Ketan Chaturvedi <Ketan.Chaturvedi@amd.com>

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@amd.com>
Co-developed-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
 arch/x86/include/uapi/asm/kvm.h |  3 ++-
 arch/x86/kvm/svm/sev.c          | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

Comments

Tom Lendacky March 17, 2025, 4:57 p.m. UTC | #1
On 3/17/25 00:23, Nikunj A Dadhania wrote:
> From: Ketan Chaturvedi <Ketan.Chaturvedi@amd.com>
> 
> 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@amd.com>
> Co-developed-by: Nikunj A Dadhania <nikunj@amd.com>
> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>

Just one minor comment below, that can be ignored unless you have to do
another version.

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>  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)
diff mbox series

Patch

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;
+
 		/*
 		 * 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)