[RFC PATCH 08/11] KVM: x86: Let moving encryption context be configurable

[Ackerley Tng <ackerleytng@google.com>]

SEV-capable VMs may also use the KVM_X86_SW_PROTECTED_VM type, but
they will still need architecture-specific handling to move encryption
context. Hence, we let moving of encryption context be configurable
and store that configuration in a flag.

Co-developed-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/include/asm/kvm_host.h | 2 ++
 arch/x86/kvm/svm/sev.c          | 2 ++
 arch/x86/kvm/x86.c              | 9 ++++++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 71c1236e4f18..ab45a3d3c867 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1445,6 +1445,8 @@ struct kvm_arch {
 	 */
 #define SPLIT_DESC_CACHE_MIN_NR_OBJECTS (SPTE_ENT_PER_PAGE + 1)
 	struct kvm_mmu_memory_cache split_desc_cache;
+
+	bool vm_move_enc_ctxt_supported;
 };
 
 struct kvm_vm_stat {
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e0e206aa3e62..b09e6477e309 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -256,6 +256,8 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		goto e_no_asid;
 	sev->asid = asid;
 
+	kvm->arch.vm_move_enc_ctxt_supported = true;
+
 	ret = sev_platform_init(&argp->error);
 	if (ret)
 		goto e_free;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 75d48379d94d..a1a28dd77b94 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6351,7 +6351,14 @@ static int kvm_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
 	if (r)
 		goto out_mark_migration_done;
 
-	r = static_call(kvm_x86_vm_move_enc_context_from)(kvm, source_kvm);
+	/*
+	 * Different types of VMs will allow userspace to define if moving
+	 * encryption context should be supported.
+	 */
+	if (kvm->arch.vm_move_enc_ctxt_supported &&
+	    kvm_x86_ops.vm_move_enc_context_from) {
+		r = static_call(kvm_x86_vm_move_enc_context_from)(kvm, source_kvm);
+	}
 
 	kvm_unlock_two_vms(kvm, source_kvm);
 out_mark_migration_done:
-- 
2.41.0.640.ga95def55d0-goog