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Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability |
Date: |
Mon, 6 Jul 2015 09:46:14 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 |
On 04/07/2015 23:19, Michael S. Tsirkin wrote:
> The fact that address_space_write/_read actually does a byteswap if
> host!=target endian should probably be documented.
FWIW, it's not if host != target endian. It's if memory region
endianness != target endianness. See memory_region_wrong_endianness.
> Or maybe it should be changed: it seems likely that non-target-specific
> devices
> that use it do this incorrectly ATM. In particular, dma_memory_rw_relaxed
> calls
> address_space_rw and since DMA originates with devices I think there's very
> little chance that these actually want a different behaviour depending on the
> target endian-ness.
>
> Most likely, these only work correctly because DMA outside RAM
> is highly unusual.
They work correctly because of that, and because most devices *and*
targets are little endian so you have no swap. On ppc64, which has
TARGET_WORDS_BIGENDIAN, it probably wouldn't work correctly.
Paolo
- [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/02
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Paolo Bonzini, 2015/07/02
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/02
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Paolo Bonzini, 2015/07/02
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/04
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Paolo Bonzini, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Peter Maydell, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Peter Maydell, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Peter Maydell, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Paolo Bonzini, 2015/07/06
- Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability, Michael S. Tsirkin, 2015/07/06