[RFC PATCH 2/5] KVM: SVM: Set TSC frequency for SecureTSC-enabled guests

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

From: Ketan Chaturvedi <Ketan.Chaturvedi@amd.com>

The SNP specification provides a desired TSC frequency parameter that can
be set as part of the SNP_LAUNCH_START command. This field has effect only
in Secure TSC enabled guests and can be used by the hypervisor to set
desired mean TSC frequency in KHz of the guest.

Signed-off-by: Ketan Chaturvedi <Ketan.Chaturvedi@amd.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
 arch/x86/include/asm/svm.h      |  1 +
 arch/x86/include/uapi/asm/kvm.h |  3 ++-
 arch/x86/kvm/svm/sev.c          |  7 +++++++
 arch/x86/kvm/svm/svm.h          | 12 ++++++++++++
 include/linux/psp-sev.h         |  2 ++
 5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index f0dea3750ca9..2bb9be9b2d30 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -289,6 +289,7 @@ static_assert((X2AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == X2AVIC_
 #define SVM_SEV_FEAT_RESTRICTED_INJECTION		BIT(3)
 #define SVM_SEV_FEAT_ALTERNATE_INJECTION		BIT(4)
 #define SVM_SEV_FEAT_DEBUG_SWAP				BIT(5)
+#define SVM_SEV_FEAT_SECURE_TSC				BIT(9)
 
 #define SVM_SEV_FEAT_INT_INJ_MODES		\
 	(SVM_SEV_FEAT_RESTRICTED_INJECTION |	\
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index bf57a824f722..c15d7c843bfd 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -834,7 +834,8 @@ struct kvm_sev_snp_launch_start {
 	__u64 policy;
 	__u8 gosvw[16];
 	__u16 flags;
-	__u8 pad0[6];
+	__u32 desired_tsc_freq;
+	__u8 pad0[2];
 	__u64 pad1[4];
 };
 
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 714c517dd4b7..ff82a644b174 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2212,6 +2212,9 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	if (sev->snp_context)
 		return -EINVAL;
 
+	if (snp_secure_tsc_enabled(kvm) && !params.desired_tsc_freq)
+		return -EINVAL;
+
 	sev->snp_context = snp_context_create(kvm, argp);
 	if (!sev->snp_context)
 		return -ENOTTY;
@@ -2232,6 +2235,10 @@ 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))
+		start.desired_tsc_freq = params.desired_tsc_freq;
+
 	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) {
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 76107c7d0595..262b638dfcb8 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -378,6 +378,18 @@ static __always_inline bool sev_snp_guest(struct kvm *kvm)
 #endif
 }
 
+static inline bool snp_secure_tsc_enabled(struct kvm *kvm)
+{
+#ifdef CONFIG_KVM_AMD_SEV
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+
+	return (sev->vmsa_features & SVM_SEV_FEAT_SECURE_TSC) &&
+	       !WARN_ON_ONCE(!sev_snp_guest(kvm));
+#else
+	return false;
+#endif
+}
+
 static inline bool ghcb_gpa_is_registered(struct vcpu_svm *svm, u64 val)
 {
 	return svm->sev_es.ghcb_registered_gpa == val;
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 903ddfea8585..fcd710f0baf8 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_freq: 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_freq;			/* In */
 	u8 gosvw[16];				/* In */
 } __packed;
 
-- 
2.34.1