[PATCH] qapi, target/i386/sev: Add cpu0-id to query-sev-capabilities

[Dov Murik <dovmurik@linux.ibm.com>]

Add a new field 'cpu0-id' to the response of query-sev-capabilities
QMP command.  The value of the field is the hex-encoded 64-byte unique
ID of the CPU0 (socket 0), which can be used to retrieve the signed CEK
of the CPU from AMD's Key Distribution Service (KDS).

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 qapi/misc-target.json |  4 ++++
 target/i386/sev.c     | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/qapi/misc-target.json b/qapi/misc-target.json
index 4bc45d2474..d9b4991c86 100644
--- a/qapi/misc-target.json
+++ b/qapi/misc-target.json
@@ -177,6 +177,8 @@
 #
 # @cert-chain:  PDH certificate chain (base64 encoded)
 #
+# @cpu0-id: 64-byte unique ID of CPU0 (hex encoded) (since 7.0)
+#
 # @cbitpos: C-bit location in page table entry
 #
 # @reduced-phys-bits: Number of physical Address bit reduction when SEV is
@@ -187,6 +189,7 @@
 { 'struct': 'SevCapability',
   'data': { 'pdh': 'str',
             'cert-chain': 'str',
+            'cpu0-id': 'str',
             'cbitpos': 'int',
             'reduced-phys-bits': 'int'},
   'if': 'TARGET_I386' }
@@ -205,6 +208,7 @@
 #
 # -> { "execute": "query-sev-capabilities" }
 # <- { "return": { "pdh": "8CCDD8DDD", "cert-chain": "888CCCDDDEE",
+#                  "cpu0-id": "5ea2e1...90ea39",
 #                  "cbitpos": 47, "reduced-phys-bits": 5}}
 #
 ##
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 025ff7a6f8..c87c69b2f3 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -82,6 +82,8 @@ struct SevGuestState {
 #define DEFAULT_GUEST_POLICY    0x1 /* disable debug */
 #define DEFAULT_SEV_DEVICE      "/dev/sev"
 
+#define SEV_UNIQUE_ID_LEN       64
+
 #define SEV_INFO_BLOCK_GUID     "00f771de-1a7e-4fcb-890e-68c77e2fb44e"
 typedef struct __attribute__((__packed__)) SevInfoBlock {
     /* SEV-ES Reset Vector Address */
@@ -531,11 +533,47 @@ e_free:
     return 1;
 }
 
+static int
+sev_get_id(int fd, guchar *id_buf, size_t id_buf_len, Error **errp)
+{
+    struct sev_user_data_get_id2 id = {
+        .address = (unsigned long)id_buf,
+        .length = id_buf_len
+    };
+    int err, r;
+
+    r = sev_platform_ioctl(fd, SEV_GET_ID2, &id, &err);
+    if (r < 0) {
+        error_setg(errp, "SEV: Failed to get ID ret=%d fw_err=%d (%s)",
+                   r, err, fw_error_to_str(err));
+        return 1;
+    }
+
+    return 0;
+}
+
+static const char hex[] = "0123456789abcdef";
+
+static gchar *hex_encode(guchar *buf, size_t len)
+{
+    gchar *str = g_new0(gchar, (len * 2) + 1);
+    size_t i;
+
+    for (i = 0; i < len; i++) {
+        str[(i * 2)] = hex[(buf[i] >> 4) & 0xf];
+        str[(i * 2) + 1] = hex[buf[i] & 0xf];
+    }
+    str[len * 2] = '\0';
+
+    return str;
+}
+
 static SevCapability *sev_get_capabilities(Error **errp)
 {
     SevCapability *cap = NULL;
     guchar *pdh_data = NULL;
     guchar *cert_chain_data = NULL;
+    guchar cpu0_id[SEV_UNIQUE_ID_LEN];
     size_t pdh_len = 0, cert_chain_len = 0;
     uint32_t ebx;
     int fd;
@@ -561,9 +599,14 @@ static SevCapability *sev_get_capabilities(Error **errp)
         goto out;
     }
 
+    if (sev_get_id(fd, cpu0_id, sizeof(cpu0_id), errp)) {
+        goto out;
+    }
+
     cap = g_new0(SevCapability, 1);
     cap->pdh = g_base64_encode(pdh_data, pdh_len);
     cap->cert_chain = g_base64_encode(cert_chain_data, cert_chain_len);
+    cap->cpu0_id = hex_encode(cpu0_id, sizeof(cpu0_id));
 
     host_cpuid(0x8000001F, 0, NULL, &ebx, NULL, NULL);
     cap->cbitpos = ebx & 0x3f;
-- 
2.25.1