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Re: [Qemu-devel] Re: [PATCH v4 0/4] virtio: Use ioeventfd for virtqueue
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] Re: [PATCH v4 0/4] virtio: Use ioeventfd for virtqueue notify |
Date: |
Wed, 17 Nov 2010 22:49:52 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Wed, Nov 17, 2010 at 08:38:25PM +0000, Stefan Hajnoczi wrote:
> On Wed, Nov 17, 2010 at 6:01 PM, Michael S. Tsirkin <address@hidden> wrote:
> > On Wed, Nov 17, 2010 at 04:19:25PM +0000, Stefan Hajnoczi wrote:
> >> The v4 version includes:
> >> * Simpler start/stop ioeventfd mechanism using bool ioeventfd_started
> >> state
> >> * Support for migration
> >> * Handle deassign race condition to avoid dropping a virtqueue kick
> >> * Add missing kvm_enabled() check to kvm_has_many_ioeventfds()
> >> * Documentation updates for qdev -device with ioeventfd=on|off
> >
> > Anthony, could you pls remind me what did you say
> > about need to stop these threads on migration vmstop?
> > Or am I confusing this with something else?
>
> Two points about the VM change state:
> 1. It is used to bring up virtio-ioeventfd on the destination host
> after migration.
> 2. It handles the race condition where a virtqueue kick is dropped
> because we deassign the ioeventfd on the source host.
>
> So I've implemented the VM change state to get correct migration behavior.
>
> The discussion you had with Anthony was more about events happening
> while the VM is paused and how that could interfere with guest state
> for migration IIRC.
>
> Stefan
Exactly. Could your patches cause a situation where block virtio ring
is used after migration stopped a VM?
--
MST
- [Qemu-devel] [PATCH v4 0/4] virtio: Use ioeventfd for virtqueue notify, Stefan Hajnoczi, 2010/11/17
- [Qemu-devel] [PATCH v4 3/4] virtio-pci: Don't use ioeventfd on old kernels, Stefan Hajnoczi, 2010/11/17
- [Qemu-devel] [PATCH v4 4/4] docs: Document virtio PCI -device ioeventfd=on|off, Stefan Hajnoczi, 2010/11/17
- [Qemu-devel] [PATCH v4 2/4] virtio-pci: Use ioeventfd for virtqueue notify, Stefan Hajnoczi, 2010/11/17
- [Qemu-devel] [PATCH v4 1/4] virtio-pci: Rename bugs field to flags, Stefan Hajnoczi, 2010/11/17
- [Qemu-devel] Re: [PATCH v4 0/4] virtio: Use ioeventfd for virtqueue notify, Michael S. Tsirkin, 2010/11/17