[Qemu-devel] [PATCH v5 11/23] sev: register the guest memory range which may contain encrypted data

[Brijesh Singh <brijesh.singh@amd.com>]

When SEV is enabled, the hardware encryption engine uses a tweak such
that the two identical plaintext at different location will have a
different ciphertexts. So swapping or moving a ciphertexts of two guest
pages will not result in plaintexts being swapped. Hence relocating
a physical backing pages of the SEV guest will require some additional
steps in KVM driver. The KVM_MEMORY_ENCRYPT_{UN,}REG_REGION ioctl can be
used to register/unregister the guest memory region which may contain the
encrypted data. KVM driver will internally handle the relocating physical
backing pages of registered memory regions.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 accel/kvm/sev.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/accel/kvm/sev.c b/accel/kvm/sev.c
index 37020751bd14..7b5318993969 100644
--- a/accel/kvm/sev.c
+++ b/accel/kvm/sev.c
@@ -84,6 +84,43 @@ fw_error_to_str(int code)
 }
 
 static void
+sev_ram_block_added(RAMBlockNotifier *n, void *host, size_t size)
+{
+    int r;
+    struct kvm_enc_region range;
+
+    range.addr = (__u64)host;
+    range.size = size;
+
+    r = kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_REG_REGION, &range);
+    if (r) {
+        error_report("%s: failed to register region (%#llx+%#llx)",
+                     __func__, range.addr, range.size);
+    }
+}
+
+static void
+sev_ram_block_removed(RAMBlockNotifier *n, void *host, size_t size)
+{
+    int r;
+    struct kvm_enc_region range;
+
+    range.addr = (__u64)host;
+    range.size = size;
+
+    r = kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_UNREG_REGION, &range);
+    if (r) {
+        error_report("%s: failed to unregister region (%#llx+%#llx)",
+                     __func__, range.addr, range.size);
+    }
+}
+
+static struct RAMBlockNotifier sev_ram_notifier = {
+    .ram_block_added = sev_ram_block_added,
+    .ram_block_removed = sev_ram_block_removed,
+};
+
+static void
 qsev_guest_finalize(Object *obj)
 {
 }
@@ -286,6 +323,8 @@ sev_guest_init(const char *id)
         goto err;
     }
 
+    ram_block_notifier_add(&sev_ram_notifier);
+
     return s;
 err:
     g_free(s);
-- 
2.9.5