[PATCH v2 4/4] KVM: SVM: Enable Secure TSC for SNP guests

[Nikunj A Dadhania <nikunj@xxxxxxx>]

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. If the frequency is not
specified by the VMM, default to 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>
---
 arch/x86/include/uapi/asm/kvm.h |  3 ++-
 arch/x86/kvm/svm/sev.c          | 20 ++++++++++++++++++++
 include/linux/psp-sev.h         |  2 ++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 9e75da97bce0..8e090cab9aa0 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];
+	__u32 desired_tsc_khz;
+	__u8 pad0[2];
 	__u64 pad1[4];
 };
 
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0a1fd5c034e2..0edd473749f7 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2228,6 +2228,20 @@ 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)) {
+		u32 user_tsc_khz = params.desired_tsc_khz;
+
+		/* Use tsc_khz if the VMM has not provided the TSC frequency */
+		if (!user_tsc_khz)
+			user_tsc_khz = tsc_khz;
+
+		start.desired_tsc_khz = user_tsc_khz;
+
+		/* Set the arch default TSC for the VM*/
+		kvm->arch.default_tsc_khz = user_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) {
@@ -2949,6 +2963,9 @@ void __init sev_set_cpu_caps(void)
 	if (sev_snp_enabled) {
 		kvm_cpu_cap_set(X86_FEATURE_SEV_SNP);
 		kvm_caps.supported_vm_types |= BIT(KVM_X86_SNP_VM);
+
+		if (cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC))
+			kvm_cpu_cap_set(X86_FEATURE_SNP_SECURE_TSC);
 	}
 }
 
@@ -3071,6 +3088,9 @@ 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 --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 903ddfea8585..613a8209bed2 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -594,6 +594,7 @@ struct sev_data_snp_addr {
  * @imi_en: launch flow is launching an IMI (Incoming Migration Image) for the
  *          purpose of guest-assisted migration.
  * @rsvd: reserved
+ * @desired_tsc_khz: hypervisor desired mean TSC freq in kHz of the guest
  * @gosvw: guest OS-visible workarounds, as defined by hypervisor
  */
 struct sev_data_snp_launch_start {
@@ -603,6 +604,7 @@ struct sev_data_snp_launch_start {
 	u32 ma_en:1;				/* In */
 	u32 imi_en:1;				/* In */
 	u32 rsvd:30;
+	u32 desired_tsc_khz;			/* In */
 	u8 gosvw[16];				/* In */
 } __packed;
 
-- 
2.43.0