Re: [PATCH] hw/i386/intel_iommu: Fix endianness problems related to VTD_IR_TableEntry

[Thomas Huth <thuth@redhat.com>]

On 02/08/2023 11.28, Thomas Huth wrote:
> The code already tries to do some endianness handling here, but
> currently fails badly:
> - While it already swaps the data when logging errors / tracing, it fails
>    to byteswap the value before e.g. accessing entry->irte.present
> - entry->irte.source_id is swapped with le32_to_cpu(), though this is
>    a 16-bit value
> - The whole union is apparently supposed to be swapped via the 64-bit
>    data[2] array, but the struct is a mixture between 32 bit values
>    (the first 8 bytes) and 64 bit values (the second 8 bytes), so this
>    cannot work as expected.
> 
> Fix it by converting the struct to two proper 64-bit bitfields, and
> by swapping the values only once for everybody right after reading
> the data from memory.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   Note: There are more endianness issues in the code, I haven't figured
>         out all of them yet, Linux fails to boot in the guest when I use
>         this device on a s390x host. But I wanted to publish this patch
>         now already since this should also fix the "issue" with the Clang
>         ms_struct packing that we recently discussed on the mailing list.

I just found the all remaining issues (I hope). I can now run a Linux guest 
with -device intel-iommu and it works without crashing now. I'll send out 
the patches shorty, after cleaning them up a little bit.

  Thomas