[PATCH v6 13/14] 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.

Also, ensure that _bss_decrypted section is marked as decrypted in the
page encryption bitmap.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 Documentation/virt/kvm/cpuid.rst     |  4 ++++
 Documentation/virt/kvm/msr.rst       | 10 ++++++++++
 arch/x86/include/asm/kvm_host.h      |  3 +++
 arch/x86/include/uapi/asm/kvm_para.h |  5 +++++
 arch/x86/kernel/kvm.c                |  4 ++++
 arch/x86/kvm/cpuid.c                 |  3 ++-
 arch/x86/kvm/svm.c                   |  5 +++++
 arch/x86/kvm/x86.c                   |  7 +++++++
 arch/x86/mm/mem_encrypt.c            | 14 +++++++++++++-
 9 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
index 01b081f6e7ea..fcb191bb3016 100644
--- a/Documentation/virt/kvm/cpuid.rst
+++ b/Documentation/virt/kvm/cpuid.rst
@@ -86,6 +86,10 @@ 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 enabling SEV live
+                                              migration feature.
+
 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/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a96ef6338cd2..ad5faaed43c0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -780,6 +780,9 @@ struct kvm_vcpu_arch {
 
 	u64 msr_kvm_poll_control;
 
+	/* SEV Live Migration MSR (AMD only) */
+	u64 msr_kvm_sev_live_migration_flag;
+
 	/*
 	 * Indicates the guest is trying to write a gfn that contains one or
 	 * more of the PTEs used to translate the write itself, i.e. the access
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/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 6efe0410fb72..8fcee0b45231 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -418,6 +418,10 @@ static void __init sev_map_percpu_data(void)
 	if (!sev_active())
 		return;
 
+	if (kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {
+		wrmsrl(MSR_KVM_SEV_LIVE_MIG_EN, KVM_SEV_LIVE_MIGRATION_ENABLED);
+	}
+
 	for_each_possible_cpu(cpu) {
 		__set_percpu_decrypted(&per_cpu(apf_reason, cpu), sizeof(apf_reason));
 		__set_percpu_decrypted(&per_cpu(steal_time, cpu), sizeof(steal_time));
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b1c469446b07..74c8b2a7270c 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -716,7 +716,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
 			     (1 << KVM_FEATURE_ASYNC_PF_VMEXIT) |
 			     (1 << KVM_FEATURE_PV_SEND_IPI) |
 			     (1 << KVM_FEATURE_POLL_CONTROL) |
-			     (1 << KVM_FEATURE_PV_SCHED_YIELD);
+			     (1 << KVM_FEATURE_PV_SCHED_YIELD) |
+			     (1 << KVM_FEATURE_SEV_LIVE_MIGRATION);
 
 		if (sched_info_on())
 			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index c99b0207a443..60ddc242a133 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7632,6 +7632,7 @@ static int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
 				  unsigned long npages, unsigned long enc)
 {
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct kvm_vcpu *vcpu = kvm->vcpus[0];
 	kvm_pfn_t pfn_start, pfn_end;
 	gfn_t gfn_start, gfn_end;
 	int ret;
@@ -7639,6 +7640,10 @@ static int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
 	if (!sev_guest(kvm))
 		return -EINVAL;
 
+	if (!(vcpu->arch.msr_kvm_sev_live_migration_flag &
+		KVM_SEV_LIVE_MIGRATION_ENABLED))
+		return -ENOTTY;
+
 	if (!npages)
 		return 0;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2127ed937f53..82867b8798f8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2880,6 +2880,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vcpu->arch.msr_kvm_poll_control = data;
 		break;
 
+	case MSR_KVM_SEV_LIVE_MIG_EN:
+		vcpu->arch.msr_kvm_sev_live_migration_flag = data;
+		break;
+
 	case MSR_IA32_MCG_CTL:
 	case MSR_IA32_MCG_STATUS:
 	case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
@@ -3126,6 +3130,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_KVM_POLL_CONTROL:
 		msr_info->data = vcpu->arch.msr_kvm_poll_control;
 		break;
+	case MSR_KVM_SEV_LIVE_MIG_EN:
+		msr_info->data = vcpu->arch.msr_kvm_sev_live_migration_flag;
+		break;
 	case MSR_IA32_P5_MC_ADDR:
 	case MSR_IA32_P5_MC_TYPE:
 	case MSR_IA32_MCG_CAP:
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index c9800fa811f6..f6a841494845 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -502,8 +502,20 @@ void __init mem_encrypt_init(void)
 	 * With SEV, we need to make a hypercall when page encryption state is
 	 * changed.
 	 */
-	if (sev_active())
+	if (sev_active()) {
+		unsigned long nr_pages;
+
 		pv_ops.mmu.page_encryption_changed = set_memory_enc_dec_hypercall;
+
+		/*
+		 * Ensure that _bss_decrypted section is marked as decrypted in the
+		 * page encryption bitmap.
+		 */
+		nr_pages = DIV_ROUND_UP(__end_bss_decrypted - __start_bss_decrypted,
+			PAGE_SIZE);
+		set_memory_enc_dec_hypercall((unsigned long)__start_bss_decrypted,
+			nr_pages, 0);
+	}
 #endif
 
 	pr_info("AMD %s active\n",
-- 
2.17.1