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Re: [Qemu-block] [Qemu-devel] [PATCH 2/6] libqos: add virtio used ring s
From: |
Fam Zheng |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH 2/6] libqos: add virtio used ring support |
Date: |
Thu, 29 Jun 2017 16:39:15 +0800 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Wed, 06/28 19:47, Stefan Hajnoczi wrote:
> Existing tests do not touch the virtqueue used ring. Instead they poll
> the virtqueue ISR register and peek into their request's device-specific
> status field.
>
> It turns out that the virtqueue ISR register can be set to 1 more than
> once for a single notification (see commit
> 83d768b5640946b7da55ce8335509df297e2c7cd "virtio: set ISR on dataplane
> notifications"). This causes problems for tests that assume a 1:1
> correspondence between the ISR being 1 and request completion.
>
> Peeking at device-specific status fields is also problematic if the
> device has no field that can be abused for EINPROGRESS polling
> semantics. This is the case if all the field's values may be set by the
> device; there's no magic constant left for polling.
>
> It's time to process the used ring for completed requests, just like a
> real virtio guest driver. This patch adds the necessary APIs.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Fam Zheng <address@hidden>
- [Qemu-block] [PATCH 0/6] virtio: use ioeventfd in TCG and qtest mode, Stefan Hajnoczi, 2017/06/28
- [Qemu-block] [PATCH 1/6] libqos: fix typo in virtio.h QVirtQueue->used comment, Stefan Hajnoczi, 2017/06/28
- [Qemu-block] [PATCH 2/6] libqos: add virtio used ring support, Stefan Hajnoczi, 2017/06/28
- Re: [Qemu-block] [Qemu-devel] [PATCH 2/6] libqos: add virtio used ring support,
Fam Zheng <=
- [Qemu-block] [PATCH 3/6] tests: fix virtio-scsi-test ISR dependence, Stefan Hajnoczi, 2017/06/28
- [Qemu-block] [PATCH 4/6] tests: fix virtio-blk-test ISR dependence, Stefan Hajnoczi, 2017/06/28
- [Qemu-block] [PATCH 5/6] tests: fix virtio-net-test ISR dependence, Stefan Hajnoczi, 2017/06/28
- [Qemu-block] [PATCH 6/6] virtio-pci: use ioeventfd even when KVM is disabled, Stefan Hajnoczi, 2017/06/28
- Re: [Qemu-block] [Qemu-devel] [PATCH 0/6] virtio: use ioeventfd in TCG and qtest mode, Eric Blake, 2017/06/28