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Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensi
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive |
Date: |
Thu, 23 Feb 2017 17:15:26 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 |
On 23/02/2017 17:08, Peter Maydell wrote:
> On 23 February 2017 at 15:58, Paolo Bonzini <address@hidden> wrote:
>> However, DEVICE_NATIVE_ENDIAN would have to be paired with tswap, which
>> the current code does not do, hence the bug. To have no swap at all,
>> you'd need DEVICE_HOST_ENDIAN.
>
> Yes, I agree that the current ramdevice code has this bug (and
> that we can fix it by any of the various options).
Good. :)
>>> AIUI what we want for this VFIO case is "when the guest does
>>> a 32-bit write of 0x12345678 then the bytes are 0x12 0x34 0x56 0x78
>>> regardless of whether TARGET_BIG_ENDIAN or not".
>>
>> No, I don't think so. This is not specific to VFIO. You can do it with
>> any device, albeit VFIO is currently the only one using ramd regions.
>
> The commit message in the patch that started this thread off
> says specifically that "VFIO PCI device is little endian".
> Is that wrong?
Yes, I think it's a red herring. Hence my initial confusion, when I
asked "would Yongji's patch just work if it used DEVICE_BIG_ENDIAN and
beNN_to_cpu/cpu_to_beNN".
Paolo
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, (continued)
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Paolo Bonzini, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Peter Maydell, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Paolo Bonzini, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Peter Maydell, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Paolo Bonzini, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Peter Maydell, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Paolo Bonzini, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Peter Maydell, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Paolo Bonzini, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Peter Maydell, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Yongji Xie, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, David Gibson, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Paul Mackerras, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Alex Williamson, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Paolo Bonzini, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Alex Williamson, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, David Gibson, 2017/02/23
- Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Alexey Kardashevskiy, 2017/02/23
Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive, Michael Roth, 2017/02/26