[RFC PATCH 4/6] hw/i386/intel_iommu: Fix VTD_IR_TableEntry for ms_struct layout

[Thomas Huth <thuth@redhat.com>]

We might want to compile QEMU with Clang on Windows - but it
does not support the __attribute__((gcc_struct)) yet. So we
have to make sure that the structs will stay the same when
the compiler uses the "ms_struct" layout. The VTD_IR_TableEntry
struct is affected - rewrite it a little bit so that it works
fine with both struct layouts.

Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 include/hw/i386/intel_iommu.h | 14 ++++++++------
 hw/i386/intel_iommu.c         |  2 +-
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index 89dcbc5e1e..08bf220393 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -204,18 +204,20 @@ union VTD_IR_TableEntry {
 #endif
         uint32_t dest_id;            /* Destination ID */
         uint16_t source_id;          /* Source-ID */
+        uint16_t __reserved_2;       /* Reserved 2 */
 #if HOST_BIG_ENDIAN
-        uint64_t __reserved_2:44;    /* Reserved 2 */
-        uint64_t sid_vtype:2;        /* Source-ID Validation Type */
-        uint64_t sid_q:2;            /* Source-ID Qualifier */
+        uint32_t __reserved_3:28;    /* Reserved 3 */
+        uint32_t sid_vtype:2;        /* Source-ID Validation Type */
+        uint32_t sid_q:2;            /* Source-ID Qualifier */
 #else
-        uint64_t sid_q:2;            /* Source-ID Qualifier */
-        uint64_t sid_vtype:2;        /* Source-ID Validation Type */
-        uint64_t __reserved_2:44;    /* Reserved 2 */
+        uint32_t sid_q:2;            /* Source-ID Qualifier */
+        uint32_t sid_vtype:2;        /* Source-ID Validation Type */
+        uint32_t __reserved_3:28;    /* Reserved 3 */
 #endif
     } QEMU_PACKED irte;
     uint64_t data[2];
 };
+QEMU_BUILD_BUG_ON(sizeof(union VTD_IR_TableEntry) != 16);
 
 #define VTD_IR_INT_FORMAT_COMPAT     (0) /* Compatible Interrupt */
 #define VTD_IR_INT_FORMAT_REMAP      (1) /* Remappable Interrupt */
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index dcc334060c..d5c5ee0751 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -3335,7 +3335,7 @@ static int vtd_irte_get(IntelIOMMUState *iommu, uint16_t index,
     }
 
     if (entry->irte.__reserved_0 || entry->irte.__reserved_1 ||
-        entry->irte.__reserved_2) {
+        entry->irte.__reserved_2 || entry->irte.__reserved_3) {
         error_report_once("%s: detected non-zero reserved IRTE "
                           "(index=%u, high=0x%" PRIx64 ", low=0x%" PRIx64 ")",
                           __func__, index, le64_to_cpu(entry->data[1]),
-- 
2.39.3