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Re: [Qemu-devel] [PATCH 0/2] VFIO: Make 8-byte accesses atomic
From: |
Alex Williamson |
Subject: |
Re: [Qemu-devel] [PATCH 0/2] VFIO: Make 8-byte accesses atomic |
Date: |
Thu, 20 Apr 2017 10:03:01 -0600 |
On Thu, 20 Apr 2017 00:19:23 -0700
Richard Henderson <address@hidden> wrote:
> On 04/19/2017 12:44 PM, Jose Ricardo Ziviani wrote:
> > This patchset has two patches:
> > [1] 8-byte writes to non-mapped MMIO are broken into pairs of 4-byte
> > writes, this patch makes such pairs atomic.
> >
> > [2] Enable 8-byte accesses in vfio_region_write and vfio_region_read.
> >
> > Patches based on master.
> >
> > Jose Ricardo Ziviani (2):
> > vfio: Set MemoryRegionOps:max_access_size and min_access_size
> > vfio: enable 8-byte reads/writes to vfio
> >
> > hw/vfio/common.c | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> >
>
> I think these patches need to be squashed to be bisectable.
No, I think it's fine. The point of patch 1/2 is to indicate that the
hardware supports 8-byte accesses, which will still be broken into 2
4-byte accesses because we don't yet set the implemented width beyond
the default. The important part is that the mutex will now group the 4
byte access pair together rather than letting them get re-ordered.
Patch 2/2 then implements native 8-byte access. I appreciate them
being separate for this subtle nuance, but maybe I'm not seeing the
same issue as you. Thanks,
Alex