On 7/28/23 07:37, Daniel P. Berrangé wrote:
On Fri, Jul 28, 2023 at 04:27:46PM +0200, Thomas Huth wrote:
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 <berra...@redhat.com>
Signed-off-by: Thomas Huth <th...@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 */
Hasn't this has changed the struct layout in the else clause
Old layout:
source_id : 16
sid_q : 2
sid_vtype : 2
reserved_2 : 44
New layout
source_id : 16
reserved_2 : 16
sid_q : 2
sid_vtype : 2
reserved_3 : 28
Was there something wrong with the change I suggested to
just make source_id be a bitfield too:
uint64_t source_id: 16; /* Source-ID */
which could make ms_struct layout avoid padding to the following
bitfields.
#endif
} QEMU_PACKED irte;
uint64_t data[2];
};
Making the point that we should never use bitfields to match hardware. This should be
converted to <hw/registerfields.h>, ARRAY_FIELD_EX64.
r~
