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Re: [Qemu-devel] [PATCH v2 6/6] vhost-user: add VFIO based accelerators
From: |
Tiwei Bie |
Subject: |
Re: [Qemu-devel] [PATCH v2 6/6] vhost-user: add VFIO based accelerators support |
Date: |
Tue, 27 Mar 2018 21:59:49 +0800 |
User-agent: |
NeoMutt/20170113 (1.7.2) |
On Thu, Mar 22, 2018 at 06:19:44PM +0200, Michael S. Tsirkin wrote:
> On Mon, Mar 19, 2018 at 03:15:37PM +0800, Tiwei Bie wrote:
[...]
> >
> > diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> > index cb3a7595aa..264a58a800 100644
> > --- a/docs/interop/vhost-user.txt
> > +++ b/docs/interop/vhost-user.txt
[...]
>
> > The accelerator
> > +context will be set for each queue independently. So the page-per-vq
> > property
> > +should also be enabled.
>
> Backend author is unlikely to know what does page-per-vq property mean.
>
> Is this intended for users maybe? docs/interop is not the best place
> for user-facing documentation.
>
> I also wonder:
>
> commit d9997d89a4a09a330a056929d06d4b7b0b7a8239
> Author: Marcel Apfelbaum <address@hidden>
> Date: Wed Sep 7 18:02:25 2016 +0300
>
> virtio-pci: reduce modern_mem_bar size
>
> Currently each VQ Notification Virtio Capability is allocated
> on a different page. The idea is to enable split drivers within
> guests, however there are no known plans to do that.
> The allocation will result in a 8MB BAR, more than various
> guest firmwares pre-allocates for PCI Bridges hotplug process.
>
> looks like enabling page per vq will break pci express hotplug.
> I suspect more work is needed to down-size the BAR to # of VQs
> actually supported.
>
I agree. Maybe we can fix the potential pci express hotplug
issue caused by enabling page-per-vq in another patch set.
Best regards,
Tiwei Bie
- [Qemu-devel] [PATCH v2 3/6] virtio: support adding sub-regions for notify region, (continued)
- [Qemu-devel] [PATCH v2 3/6] virtio: support adding sub-regions for notify region, Tiwei Bie, 2018/03/19
- [Qemu-devel] [PATCH v2 4/6] vfio: support getting VFIOGroup from groupfd, Tiwei Bie, 2018/03/19
- [Qemu-devel] [PATCH v2 5/6] vfio: remove DPRINTF() definition from vfio-common.h, Tiwei Bie, 2018/03/19
- [Qemu-devel] [PATCH v2 6/6] vhost-user: add VFIO based accelerators support, Tiwei Bie, 2018/03/19
- Re: [Qemu-devel] [PATCH v2 0/6] Extend vhost-user to support VFIO based accelerators, Michael S. Tsirkin, 2018/03/22
- Re: [Qemu-devel] [PATCH v2 0/6] Extend vhost-user to support VFIO based accelerators, Michael S. Tsirkin, 2018/03/22