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Re: [Xen-devel] [Qemu-devel] [PATCH v6 20/26] memory: Access MemoryRegion with endianness
- To: Richard Henderson <richard.henderson@xxxxxxxxxx>, tony.nguyen@xxxxxx, qemu-devel@xxxxxxxxxx
- From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
- Date: Wed, 7 Aug 2019 20:00:34 +0200
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- Delivery-date: Wed, 07 Aug 2019 18:00:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 07/08/19 19:49, Richard Henderson wrote:
> On 8/7/19 1:33 AM, tony.nguyen@xxxxxx wrote:
>> @@ -551,6 +551,7 @@ void virtio_address_space_write(VirtIOPCIProxy *proxy,
>> hwaddr addr,
>> /* As length is under guest control, handle illegal values. */
>> return;
>> }
>> + /* FIXME: memory_region_dispatch_write ignores MO_BSWAP. */
>> memory_region_dispatch_write(mr, addr, val, size_memop(len),
>> MEMTXATTRS_UNSPECIFIED);
>> }
>
> Here is an example of where Paolo is quite right -- you cannot simply add
> MO_TE
> via size_memop(). In patch 22 we see
>
>> @@ -542,16 +542,15 @@ void virtio_address_space_write(VirtIOPCIProxy *proxy,
>> hwaddr addr,
>> val = pci_get_byte(buf);
>> break;
>> case 2:
>> - val = cpu_to_le16(pci_get_word(buf));
>> + val = pci_get_word(buf);
>> break;
>> case 4:
>> - val = cpu_to_le32(pci_get_long(buf));
>> + val = pci_get_long(buf);
>> break;
>> default:
>> /* As length is under guest control, handle illegal values. */
>> return;
>> }
>> - /* FIXME: memory_region_dispatch_write ignores MO_BSWAP. */
>> memory_region_dispatch_write(mr, addr, val, size_memop(len),
>> MEMTXATTRS_UNSPECIFIED);
>
> This is a little-endian store -- MO_LE not MO_TE.
Or leave the switch statement aside and request host endianness. Either
is fine.
Paolo
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