[PATCH v6 4/4] KVM: SVM: Enable Secure TSC for SNP guests

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

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>
Tested-by: Vaishali Thakkar <vaishali.thakkar@suse.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@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          | 15 ++++++++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 460306b35a4b..075af0dcee25 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -839,7 +839,8 @@ 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 50263b473f95..bcb262ff42bb 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2205,6 +2205,14 @@ 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) {
@@ -2445,7 +2453,9 @@ static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
 			return ret;
 		}
 
-		svm->vcpu.arch.guest_state_protected = true;
+		vcpu->arch.guest_state_protected = true;
+		vcpu->arch.guest_tsc_protected = snp_secure_tsc_enabled(kvm);
+
 		/*
 		 * SEV-ES (and thus SNP) guest mandates LBR Virtualization to
 		 * be _always_ ON. Enable it only after setting
@@ -3059,6 +3069,9 @@ 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)
-- 
2.43.0