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Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianne
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness() |
Date: |
Thu, 27 Aug 2015 13:53:45 +0300 |
On Thu, Aug 27, 2015 at 11:49:32AM +0100, Peter Maydell wrote:
> On 27 August 2015 at 05:50, Jason Wang <address@hidden> wrote:
> > On 08/26/2015 10:51 PM, Greg Kurz wrote:
> >> On Wed, 26 Aug 2015 15:21:59 +0100
> >> Peter Maydell <address@hidden> wrote:
> >>> This seems to me like a bug in the caller. Why would anything
> >>> try to call into the memory subsystem to do a zero-size
> >>> transaction?
>
> >> Here's the patch which needs zero-size eventfd:
> >>
> >> http://patchwork.ozlabs.org/patch/509428/
>
> > Yes, this is because we want to use wildcard mmio eventfd (which
> > requires size to be zero) to speed up virtio 1.0 mmio.
>
> But *why* does it require the size to be zero? I still think
> the caller should just avoid trying to do zero-size memory
> operations: they don't make sense. What is a zero size
> operation supposed to mean?
>
> -- PMM
This just mirrors an API we have in kvm: if you pass 0
size when registering an ioeventfd, it will match on access
of any size.
--
MST
- [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Jason Wang, 2015/08/26
- [Qemu-devel] [PATCH 2/2] pci: test-dev: try to test fast mmio bus for wildcard mmio event, Jason Wang, 2015/08/26
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Peter Maydell, 2015/08/26
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Greg Kurz, 2015/08/26
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Jason Wang, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Peter Maydell, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(),
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Peter Maydell, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Michael S. Tsirkin, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Peter Maydell, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Michael S. Tsirkin, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Peter Maydell, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Michael S. Tsirkin, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Peter Maydell, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Michael S. Tsirkin, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Greg Kurz, 2015/08/27
- Re: [Qemu-devel] [PATCH 1/2] memory: allow zero size for adjust_endianness(), Jason Wang, 2015/08/27