Re: [Qemu-devel] [PATCH v5 11/15] memory: Single byte swap along the I/O path
On 7/26/19 2:39 AM, Paolo Bonzini wrote:
> Then memory_region_endianness_inverted can be:
>
> if (mr->ops->endianness == DEVICE_NATIVE_ENDIAN)
> return (op & MO_BSWAP) != MO_TE;
> else if (mr->ops->endianness == DEVICE_BIG_ENDIAN)
> return (op & MO_BSWAP) != MO_BE;
> else if (mr->ops->endianness == DEVICE_LITTLE_ENDIAN)
> return (op & MO_BSWAP) != MO_LE;
Possibly outside the scope of this patch set, I'd like to replace enum
device_endian with MemOp, with exactly the above enumerator replacement.
In the meantime, perhaps a conversion function
static MemOp devendian_memop(enum device_endian d)
{
switch (d) {
case DEVICE_NATIVE_ENDIAN:
return MO_TE;
case DEVICE_BIG_ENDIAN:
return MO_BE;
case DEVICE_LITTLE_ENDIAN:
return MO_LE;
default:
g_assert_not_reached();
}
}
With that, this would simplify to
return (op & MO_BSWAP) != devendian_memop(mr->ops->endianness);
> I think the changes should be split in two parts. Before this patch,
> you modify all callers of memory_region_dispatch_* so that they already
> pass the right endianness op; however, you leave the existing swap in
> place. So for example in load_helper you'd have in a previous patch
>
> +/* FIXME: io_readx ignores MO_BSWAP. */
> +op = SIZE_MEMOP(size) | (big_endian ? MO_BE : MO_LE);
> res = io_readx(env, _tlb(env)->d[mmu_idx].iotlb[index],
> - mmu_idx, addr, retaddr, access_type,
> SIZE_MEMOP(size));
> + mmu_idx, addr, retaddr, access_type, op);
> return handle_bswap(res, size, big_endian);
>
> Then, in this patch, you remove the handle_bswap call as well as the
> FIXME comment.
Agreed.
r~
Re: [Qemu-devel] [PATCH v5 11/15] memory: Single byte swap along the I/O path
On 7/26/19 2:26 AM, Paolo Bonzini wrote:
> On 26/07/19 08:47, tony.ngu...@bt.com wrote:
>> + op = SIZE_MEMOP(size);
>> + if (need_bswap(big_endian)) {
>> + op ^= MO_BSWAP;
>> + }
>
> And this has the same issue as the first version. It should be
>
> op = SIZE_MEMOP(size) | (big_endian ? MO_BE : MO_LE);
>
> and everything should work. If it doesn't (and indeed it doesn't :)) it
> means you have bugs somewhere else.
As I mentioned against patch 9, which also touches this area, it should be
using the MemOp that is already passed in to this function instead of building
a new one from scratch.
But, yes, any failure in that would mean bugs somewhere else. ;-)
r~
Re: [Qemu-devel] [PATCH v5 11/15] memory: Single byte swap along the I/O path
On 26/07/19 08:47, tony.ngu...@bt.com wrote:
> +static bool memory_region_endianness_inverted(MemoryRegion *mr)
> {
> #ifdef TARGET_WORDS_BIGENDIAN
> return mr->ops->endianness == DEVICE_LITTLE_ENDIAN;
> @@ -361,23 +361,27 @@ static bool
> memory_region_wrong_endianness(MemoryRegion *mr)
> #endif
> }
>
> -static void adjust_endianness(MemoryRegion *mr, uint64_t *data,
> unsigned size)
> +static void adjust_endianness(MemoryRegion *mr, uint64_t *data, MemOp op)
> {
> - if (memory_region_wrong_endianness(mr)) {
> - switch (size) {
> - case 1:
> + if (memory_region_endianness_inverted(mr)) {
> + op ^= MO_BSWAP;
> + }
Here it should not matter: the caller of memory_region_dispatch_read
should includes one of MO_TE/MO_LE/MO_BE in the op (or nothing for host
endianness). Then memory_region_endianness_inverted can be:
if (mr->ops->endianness == DEVICE_NATIVE_ENDIAN)
return (op & MO_BSWAP) != MO_TE;
else if (mr->ops->endianness == DEVICE_BIG_ENDIAN)
return (op & MO_BSWAP) != MO_BE;
else if (mr->ops->endianness == DEVICE_LITTLE_ENDIAN)
return (op & MO_BSWAP) != MO_LE;
and adjust_endianness does
if (memory_region_endianness_inverted(mr, op)) {
switch (op & MO_SIZE) {
...
}
}
I think the changes should be split in two parts. Before this patch,
you modify all callers of memory_region_dispatch_* so that they already
pass the right endianness op; however, you leave the existing swap in
place. So for example in load_helper you'd have in a previous patch
+/* FIXME: io_readx ignores MO_BSWAP. */
+op = SIZE_MEMOP(size) | (big_endian ? MO_BE : MO_LE);
res = io_readx(env, _tlb(env)->d[mmu_idx].iotlb[index],
- mmu_idx, addr, retaddr, access_type,
SIZE_MEMOP(size));
+ mmu_idx, addr, retaddr, access_type, op);
return handle_bswap(res, size, big_endian);
Then, in this patch, you remove the handle_bswap call as well as the
FIXME comment.
Paolo
Re: [Qemu-devel] [PATCH v5 11/15] memory: Single byte swap along the I/O path
On 26/07/19 08:47, tony.ngu...@bt.com wrote:
> + op = SIZE_MEMOP(size);
> + if (need_bswap(big_endian)) {
> + op ^= MO_BSWAP;
> + }
And this has the same issue as the first version. It should be
op = SIZE_MEMOP(size) | (big_endian ? MO_BE : MO_LE);
and everything should work. If it doesn't (and indeed it doesn't :)) it
means you have bugs somewhere else.
Paolo
