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Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface
From: |
Laszlo Ersek |
Subject: |
Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface |
Date: |
Sat, 8 Aug 2015 00:58:08 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 08/07/15 22:40, Kevin O'Connor wrote:
> On Thu, Aug 06, 2015 at 04:59:15PM +0200, Marc Marí wrote:
>> On Thu, 6 Aug 2015 10:47:21 -0400
>> "Kevin O'Connor" <address@hidden> wrote:
>>> Also, it's very unusual to see 32bit writes to an unaligned IO address
>>> - I think two pad bytes should be added so that the offset for the dma
>>> address is at position 4 (instead of 2).
>>
>> This is a PIO port (out), not a MMIO access (write). Maybe I'm wrong,
>> but I don't think it matters to have the port number aligned with the
>> write size.
>
> There was a thread on misaligned IO accesses recently:
>
> http://lists.nongnu.org/archive/html/qemu-devel/2015-07/msg05054.html
>
> Perhaps Stefan knows what the implications of misaligned IO writes
> are.
>
> I suspect it's better to avoid them.
Unrelated, but I just noticed: in (and since) commit 457ba42878,
ICH9_LPC_GEN_PMCON_1 is read with pci_config_read*w*, but rewritten with
pci_config_write*l*.
Is that intended? (My similar OVMF code writes a word, not a long.)
Thanks
Laszlo
- [Qemu-devel] QEMU fw_cfg DMA interface, Marc Marí, 2015/08/06
- Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface, Laszlo Ersek, 2015/08/06
- Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface, Marc Marí, 2015/08/06
- Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface, Laszlo Ersek, 2015/08/06
- Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface, Marc Marí, 2015/08/07
- Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface, Eric Blake, 2015/08/07
[Qemu-devel] [PATCH 4/5] Enable fw_cfg DMA interface for ARM, Marc Marí, 2015/08/06
[Qemu-devel] [PATCH 5/5] Enable fw_cfg DMA interface for x86, Marc Marí, 2015/08/06
Re: [Qemu-devel] QEMU fw_cfg DMA interface, Stefan Hajnoczi, 2015/08/06