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Re: [Qemu-devel] [PATCH 0/5] Support more virtio queues
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH 0/5] Support more virtio queues |
Date: |
Fri, 6 Feb 2015 16:26:26 +0000 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Fri, Feb 06, 2015 at 03:54:08PM +0800, Jason Wang wrote:
> We current limit the max virtio queues to 64. This is not sufficient
> to support some multiqueue deivces (e.g recent Linux support up to 256
> tap queues). So this series try to let virtio to support more queues.
>
> No much works needs to be done except:
>
> - Patch 1 renames VIRTIO_PCI_QUEUE_MAX to a more generic name:
> VIRTIO_QUEUE_MAX
> - Patch 2 simply increase the the limitation to 513 (256 queue pairs)
> - Patch 3 fixes a bug in virtio_del_queue()
> - Patch 4 tries to remove the hard coded MSI-X bar size (4096) and allow up to
> 2048 MSI-X entries.
> - Patch 5 add a boolean property to let the virtio-net can calculate
> the MSI-X bar size based on the number of MSI-X vectors and keep
> migration compability with legacy version whose bar size is 4096.
>
> With this patch, we can support up to 256 queues.Since x86 can only
> allow about 240 interrupt vectors for MSI-X, current Linux driver can
> only have about 80 queue pairs has their private MSI-X interrupt
> vectors. With sharing IRQ with queue pairs (RFC posted in
> https://lkml.org/lkml/2014/12/25/169), Linux driver can have up
> to about 186 queue pairs has their private MSI-X interrupt vectors.
Worth mentioning that the change to VIRTIO_QUEUE_MAX is safe from a live
migration perspective:
Old QEMUs will not accept migration from new QEMUs launched with >64
queues:
Invalid number of PCI queues: 0x41
Other than that, live migration works fine.
Stefan
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- [Qemu-devel] [PATCH 2/5] virtio: increase VIRITO_QUEUE_MAX to 513, (continued)
- [Qemu-devel] [PATCH 2/5] virtio: increase VIRITO_QUEUE_MAX to 513, Jason Wang, 2015/02/06
- [Qemu-devel] [PATCH 1/5] virtio: rename VIRTIO_PCI_QUEUE_MAX to VIRTIO_QUEUE_MAX, Jason Wang, 2015/02/06
- [Qemu-devel] [PATCH 3/5] virtio-net: fix the upper bound when trying to delete queues, Jason Wang, 2015/02/06
- [Qemu-devel] [PATCH 4/5] pci: remove hard-coded bar size in msix_init_exclusive_bar(), Jason Wang, 2015/02/06
- [Qemu-devel] [PATCH 5/5] virtio-pci: introduce auto_msix_bar_size property, Jason Wang, 2015/02/06
- Re: [Qemu-devel] [PATCH 0/5] Support more virtio queues,
Stefan Hajnoczi <=