On Thu, Jul 02, 2020 at 07:12:08AM -0400, Michael S. Tsirkin wrote:
> memory: align to min access size
>
> If impl.min_access_size > valid.min_access_size access callbacks
> can get a misaligned access as size is increased.
> They don't expect that, let's fix it in the memory core.
>
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
>
> ---
>
>
> diff --git a/memory.c b/memory.c
> index 9200b20130..ea489ce405 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -532,6 +532,7 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
> }
>
> /* FIXME: support unaligned access? */
> + addr &= ~(access_size_min - 1);
> access_size = MAX(MIN(size, access_size_max), access_size_min);
> access_mask = MAKE_64BIT_MASK(0, access_size * 8);
> if (memory_region_big_endian(mr)) {
I've tried this (and .impl.min_access_size=2) but that wasn't enough.
In the guest, I did `inb(base_addr + 1)`, but I've got back the value as
if `inb(base_addr)` was run.
The device emulation read callbacks did get addr=0 width=2, so that's
fine, but the result returned to the guest wasn't shifted. Same thing
for write access, the write value isn't shifted, so a write to the
second byte would be written to the first.
Thanks,
--
Anthony PERARD
