sev/i386: add support to LAUNCH_MEASURE command

During machine creation we encrypted the guest bios image, the
LAUNCH_MEASURE command can be used to retrieve the measurement of
the encrypted memory region. This measurement is a signature of
the memory contents that can be sent to the guest owner as an
attestation that the memory was encrypted correctly by the firmware.
VM management tools like libvirt can query the measurement using
query-sev-launch-measure QMP command.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/target/i386/sev.c b/target/i386/sev.c
index 2d14879166..0132beaf24 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -516,6 +516,68 @@ sev_launch_update_data(uint8_t *addr, uint64_t len)
     return ret;
 }
 
+static void
+sev_launch_get_measure(Notifier *notifier, void *unused)
+{
+    int ret, error;
+    guchar *data;
+    SEVState *s = sev_state;
+    struct kvm_sev_launch_measure *measurement;
+
+    if (!sev_check_state(SEV_STATE_LAUNCH_UPDATE)) {
+        return;
+    }
+
+    measurement = g_new0(struct kvm_sev_launch_measure, 1);
+
+    /* query the measurement blob length */
+    ret = sev_ioctl(sev_state->sev_fd, KVM_SEV_LAUNCH_MEASURE,
+                    measurement, &error);
+    if (!measurement->len) {
+        error_report("%s: LAUNCH_MEASURE ret=%d fw_error=%d '%s'",
+                     __func__, ret, error, fw_error_to_str(errno));
+        goto free_measurement;
+    }
+
+    data = g_new0(guchar, measurement->len);
+    measurement->uaddr = (unsigned long)data;
+
+    /* get the measurement blob */
+    ret = sev_ioctl(sev_state->sev_fd, KVM_SEV_LAUNCH_MEASURE,
+                    measurement, &error);
+    if (ret) {
+        error_report("%s: LAUNCH_MEASURE ret=%d fw_error=%d '%s'",
+                     __func__, ret, error, fw_error_to_str(errno));
+        goto free_data;
+    }
+
+    sev_set_guest_state(SEV_STATE_LAUNCH_SECRET);
+
+    /* encode the measurement value and emit the event */
+    s->measurement = g_base64_encode(data, measurement->len);
+    trace_kvm_sev_launch_measurement(s->measurement);
+
+free_data:
+    g_free(data);
+free_measurement:
+    g_free(measurement);
+}
+
+char *
+sev_get_launch_measurement(void)
+{
+    if (sev_state &&
+        sev_state->state >= SEV_STATE_LAUNCH_SECRET) {
+        return g_strdup(sev_state->measurement);
+    }
+
+    return NULL;
+}
+
+static Notifier sev_machine_done_notify = {
+    .notify = sev_launch_get_measure,
+};
+
 void *
 sev_guest_init(const char *id)
 {
@@ -593,6 +655,7 @@ sev_guest_init(const char *id)
     }
 
     ram_block_notifier_add(&sev_ram_notifier);
+    qemu_add_machine_init_done_notifier(&sev_machine_done_notify);
 
     return s;
 err: