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Re: [Qemu-devel] [PATCH 17/33] virtio-pci: add flags to enable/disable l
From: |
Gerd Hoffmann |
Subject: |
Re: [Qemu-devel] [PATCH 17/33] virtio-pci: add flags to enable/disable legacy/modern |
Date: |
Thu, 04 Jun 2015 17:13:27 +0200 |
On Do, 2015-06-04 at 11:52 +0100, Daniel P. Berrange wrote:
> On Thu, Jun 04, 2015 at 12:34:26PM +0200, Gerd Hoffmann wrote:
> > Add VIRTIO_PCI_FLAG_DISABLE_LEGACY and VIRTIO_PCI_FLAG_DISABLE_MODERN
> > for VirtIOPCIProxy->flags. Also add properties for them. They can be
> > used to disable modern (virtio 1.0) or legacy (virtio 0.9) modes.
> >
> > By default only legacy is advertized, modern will be turned on by
> > default once all remaining spec compilance issues are addressed.
>
> What is the reason for adding these flags? From the pov of management
> app integration I think we'd really want the front/back to be automatically
> negotiating the right compatible featureset. Having mgmt need to set these
> legacy/modern flags based on guest OS needs seems rather painful. As such
> I'd be really loathe to support these in libvirt
Usually there should be no need to muck with these, except for
development and testing purposes. And of course we need them so we can
turn off virtio 1.0 for old machine types via compat properties (once we
flip the switch to enable virtio-1.0 by default).
libvirt support for these in the domain xml syntax goes into
"nice-to-have" category, but I can equally well live without them and
use the <qemu:*> tags to set them if needed.
Support for them higher up in the management stack should not be needed.
cheers,
Gerd
- [Qemu-devel] [PATCH 07/33] virtio-net: no writeable mac for virtio-1, (continued)
- [Qemu-devel] [PATCH 07/33] virtio-net: no writeable mac for virtio-1, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 05/33] virtio: disallow late feature changes for virtio-1, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 01/33] virtio: 64bit features fixups., Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 09/33] virtio-net: enable virtio 1.0, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 10/33] vhost_net: add version_1 feature, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 03/33] virtio: allow virtio-1 queue layout, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 02/33] virtio: endianness checks for virtio 1.0 devices, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 17/33] virtio-pci: add flags to enable/disable legacy/modern, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 08/33] virtio-net: support longer header, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 15/33] virtio: add modern config accessors, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 14/33] virtio: generation counter support, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 21/33] virtio-pci: correctly set host notifiers for modern bar, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 16/33] virtio-pci: switch to modern accessors for 1.0, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 11/33] vhost: 64 bit features, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 22/33] virtio_balloon: header update, Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 19/33] virtio-pci: change & document virtio pci bar layout., Gerd Hoffmann, 2015/06/04
- [Qemu-devel] [PATCH 29/33] virtio-pci: drop identical virtio_pci_cap, Gerd Hoffmann, 2015/06/04