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];
> };
With regards,
Daniel
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