hw/i386/amd_iommu: Fix IOMMU event log encoding errors

Coverity issues several UNINIT warnings against amd_iommu.c [1]. This
patch fixes them by clearing evt before encoding. On top of it, this
patch changes the event log size to 16 bytes per IOMMU specification,
and fixes the event log entry format in amdvi_encode_event().

[1] CID 1487116/1487200/1487190/1487232/1487115/1487258

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Message-Id: <20220422055146.3312226-1-wei.huang2@amd.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/i386/amd_iommu.c

@@ -201,15 +201,18 @@ static void amdvi_setevent_bits(uint64_t *buffer, uint64_t value, int start,
 /*
  * AMDVi event structure
  *    0:15   -> DeviceID
- *    55:63  -> event type + miscellaneous info
- *    63:127 -> related address
+ *    48:63  -> event type + miscellaneous info
+ *    64:127 -> related address
  */
 static void amdvi_encode_event(uint64_t *evt, uint16_t devid, uint64_t addr,
                                uint16_t info)
 {
+    evt[0] = 0;
+    evt[1] = 0;
+
     amdvi_setevent_bits(evt, devid, 0, 16);
-    amdvi_setevent_bits(evt, info, 55, 8);
-    amdvi_setevent_bits(evt, addr, 63, 64);
+    amdvi_setevent_bits(evt, info, 48, 16);
+    amdvi_setevent_bits(evt, addr, 64, 64);
 }
 /* log an error encountered during a page walk
  *
@@ -218,7 +221,7 @@ static void amdvi_encode_event(uint64_t *evt, uint16_t devid, uint64_t addr,
 static void amdvi_page_fault(AMDVIState *s, uint16_t devid,
                              hwaddr addr, uint16_t info)
 {
-    uint64_t evt[4];
+    uint64_t evt[2];
 
     info |= AMDVI_EVENT_IOPF_I | AMDVI_EVENT_IOPF;
     amdvi_encode_event(evt, devid, addr, info);
@@ -234,7 +237,7 @@ static void amdvi_page_fault(AMDVIState *s, uint16_t devid,
 static void amdvi_log_devtab_error(AMDVIState *s, uint16_t devid,
                                    hwaddr devtab, uint16_t info)
 {
-    uint64_t evt[4];
+    uint64_t evt[2];
 
     info |= AMDVI_EVENT_DEV_TAB_HW_ERROR;
 
@@ -248,7 +251,8 @@ static void amdvi_log_devtab_error(AMDVIState *s, uint16_t devid,
  */
 static void amdvi_log_command_error(AMDVIState *s, hwaddr addr)
 {
-    uint64_t evt[4], info = AMDVI_EVENT_COMMAND_HW_ERROR;
+    uint64_t evt[2];
+    uint16_t info = AMDVI_EVENT_COMMAND_HW_ERROR;
 
     amdvi_encode_event(evt, 0, addr, info);
     amdvi_log_event(s, evt);
@@ -261,7 +265,7 @@ static void amdvi_log_command_error(AMDVIState *s, hwaddr addr)
 static void amdvi_log_illegalcom_error(AMDVIState *s, uint16_t info,
                                        hwaddr addr)
 {
-    uint64_t evt[4];
+    uint64_t evt[2];
 
     info |= AMDVI_EVENT_ILLEGAL_COMMAND_ERROR;
     amdvi_encode_event(evt, 0, addr, info);
@@ -276,7 +280,7 @@ static void amdvi_log_illegalcom_error(AMDVIState *s, uint16_t info,
 static void amdvi_log_illegaldevtab_error(AMDVIState *s, uint16_t devid,
                                           hwaddr addr, uint16_t info)
 {
-    uint64_t evt[4];
+    uint64_t evt[2];
 
     info |= AMDVI_EVENT_ILLEGAL_DEVTAB_ENTRY;
     amdvi_encode_event(evt, devid, addr, info);
@@ -288,7 +292,7 @@ static void amdvi_log_illegaldevtab_error(AMDVIState *s, uint16_t devid,
 static void amdvi_log_pagetab_error(AMDVIState *s, uint16_t devid,
                                     hwaddr addr, uint16_t info)
 {
-    uint64_t evt[4];
+    uint64_t evt[2];
 
     info |= AMDVI_EVENT_PAGE_TAB_HW_ERROR;
     amdvi_encode_event(evt, devid, addr, info);