[PATCH v8 13/18] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR.

[Ashish Kalra <Ashish.Kalra@amd.com>]

From: Ashish Kalra <ashish.kalra@amd.com>

Add new KVM_FEATURE_SEV_LIVE_MIGRATION feature for guest to check
for host-side support for SEV live migration. Also add a new custom
MSR_KVM_SEV_LIVE_MIG_EN for guest to enable the SEV live migration
feature.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 Documentation/virt/kvm/cpuid.rst     |  5 +++++
 Documentation/virt/kvm/msr.rst       | 10 ++++++++++
 arch/x86/include/uapi/asm/kvm_para.h |  5 +++++
 arch/x86/kvm/svm/sev.c               | 14 ++++++++++++++
 arch/x86/kvm/svm/svm.c               | 16 ++++++++++++++++
 arch/x86/kvm/svm/svm.h               |  2 ++
 6 files changed, 52 insertions(+)

diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
index 01b081f6e7ea..0514523e00cd 100644
--- a/Documentation/virt/kvm/cpuid.rst
+++ b/Documentation/virt/kvm/cpuid.rst
@@ -86,6 +86,11 @@ KVM_FEATURE_PV_SCHED_YIELD        13          guest checks this feature bit
                                               before using paravirtualized
                                               sched yield.
 
+KVM_FEATURE_SEV_LIVE_MIGRATION    14          guest checks this feature bit before
+                                              using the page encryption state
+                                              hypercall to notify the page state
+                                              change
+
 KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24          host will warn if no guest-side
                                               per-cpu warps are expeced in
                                               kvmclock
diff --git a/Documentation/virt/kvm/msr.rst b/Documentation/virt/kvm/msr.rst
index 33892036672d..7cd7786bbb03 100644
--- a/Documentation/virt/kvm/msr.rst
+++ b/Documentation/virt/kvm/msr.rst
@@ -319,3 +319,13 @@ data:
 
 	KVM guests can request the host not to poll on HLT, for example if
 	they are performing polling themselves.
+
+MSR_KVM_SEV_LIVE_MIG_EN:
+        0x4b564d06
+
+	Control SEV Live Migration features.
+
+data:
+        Bit 0 enables (1) or disables (0) host-side SEV Live Migration feature.
+        Bit 1 enables (1) or disables (0) support for SEV Live Migration extensions.
+        All other bits are reserved.
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 2a8e0b6b9805..d9d4953b42ad 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -31,6 +31,7 @@
 #define KVM_FEATURE_PV_SEND_IPI	11
 #define KVM_FEATURE_POLL_CONTROL	12
 #define KVM_FEATURE_PV_SCHED_YIELD	13
+#define KVM_FEATURE_SEV_LIVE_MIGRATION	14
 
 #define KVM_HINTS_REALTIME      0
 
@@ -50,6 +51,7 @@
 #define MSR_KVM_STEAL_TIME  0x4b564d03
 #define MSR_KVM_PV_EOI_EN      0x4b564d04
 #define MSR_KVM_POLL_CONTROL	0x4b564d05
+#define MSR_KVM_SEV_LIVE_MIG_EN	0x4b564d06
 
 struct kvm_steal_time {
 	__u64 steal;
@@ -122,4 +124,7 @@ struct kvm_vcpu_pv_apf_data {
 #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
 #define KVM_PV_EOI_DISABLED 0x0
 
+#define KVM_SEV_LIVE_MIGRATION_ENABLED			(1 << 0)
+#define KVM_SEV_LIVE_MIGRATION_EXTENSIONS_SUPPORTED	(1 << 1)
+
 #endif /* _UAPI_ASM_X86_KVM_PARA_H */
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index c0d7043a0627..6f69c3a47583 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1469,6 +1469,17 @@ int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
 	return 0;
 }
 
+void sev_update_migration_flags(struct kvm *kvm, u64 data)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+
+	if (!sev_guest(kvm))
+		return;
+
+	if (data & KVM_SEV_LIVE_MIGRATION_ENABLED)
+		sev->live_migration_enabled = true;
+}
+
 int svm_get_page_enc_bitmap(struct kvm *kvm,
 				   struct kvm_page_enc_bitmap *bmap)
 {
@@ -1481,6 +1492,9 @@ int svm_get_page_enc_bitmap(struct kvm *kvm,
 	if (!sev_guest(kvm))
 		return -ENOTTY;
 
+	if (!sev->live_migration_enabled)
+		return -EINVAL;
+
 	gfn_start = bmap->start_gfn;
 	gfn_end = gfn_start + bmap->num_pages;
 
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 442adbbb0641..a99f5457f244 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2633,6 +2633,9 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		svm->msr_decfg = data;
 		break;
 	}
+	case MSR_KVM_SEV_LIVE_MIG_EN:
+		sev_update_migration_flags(vcpu->kvm, data);
+		break;
 	case MSR_IA32_APICBASE:
 		if (kvm_vcpu_apicv_active(vcpu))
 			avic_update_vapic_bar(to_svm(vcpu), data);
@@ -3493,6 +3496,19 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
 	svm->nrips_enabled = kvm_cpu_cap_has(X86_FEATURE_NRIPS) &&
 			     guest_cpuid_has(&svm->vcpu, X86_FEATURE_NRIPS);
 
+        /*
+         * If SEV guest then enable the Live migration feature.
+         */
+        if (sev_guest(vcpu->kvm)) {
+              struct kvm_cpuid_entry2 *best;
+
+              best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
+              if (!best)
+                      return;
+
+              best->eax |= (1 << KVM_FEATURE_SEV_LIVE_MIGRATION);
+        }
+
 	if (!kvm_vcpu_apicv_active(vcpu))
 		return;
 
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index fd99e0a5417a..77f132a6fead 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -65,6 +65,7 @@ struct kvm_sev_info {
 	int fd;			/* SEV device fd */
 	unsigned long pages_locked; /* Number of pages locked */
 	struct list_head regions_list;  /* List of registered regions */
+	bool live_migration_enabled;
 	unsigned long *page_enc_bmap;
 	unsigned long page_enc_bmap_size;
 };
@@ -494,5 +495,6 @@ int svm_unregister_enc_region(struct kvm *kvm,
 void pre_sev_run(struct vcpu_svm *svm, int cpu);
 int __init sev_hardware_setup(void);
 void sev_hardware_teardown(void);
+void sev_update_migration_flags(struct kvm *kvm, u64 data);
 
 #endif
-- 
2.17.1