[PATCH 2/2] target-i386: sev: fail query-sev-capabilities if QEMU cannot use SEV

[Paolo Bonzini]

In some cases, such as if the kvm-amd "sev" module parameter is set
to 0, SEV will be unavailable but query-sev-capabilities will still
return all the information.  This tricks libvirt into erroneously
reporting that SEV is available.  Check the actual usability of the
feature and return the appropriate error if QEMU cannot use KVM
or KVM cannot use SEV.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 target/i386/sev.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/target/i386/sev.c b/target/i386/sev.c
index 70f9ee026f..22194b3e32 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -450,6 +450,15 @@ sev_get_capabilities(Error **errp)
     uint32_t ebx;
     int fd;
 
+    if (!kvm_enabled()) {
+        error_setg(errp, "KVM not enabled\n");
+        return NULL;
+    }
+    if (kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_OP, NULL) < 0) {
+        error_setg(errp, "SEV is not enabled\n");
+        return NULL;
+    }
+
     fd = open(DEFAULT_SEV_DEVICE, O_RDWR);
     if (fd < 0) {
         error_setg_errno(errp, errno, "Failed to open %s",
-- 
2.26.2