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Re: [Qemu-devel] [PATCH 3/3] virtio-blk: note optional features
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 3/3] virtio-blk: note optional features |
Date: |
Tue, 06 Mar 2012 16:58:26 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120216 Thunderbird/10.0.1 |
Il 06/03/2012 15:53, Michael S. Tsirkin ha scritto:
> > The guest must already be prepared to see SG_IO support
> > disappear from under its feet, for example if migration
> > refers to a block device on the source and file-based
> > storage on the destination; or more likely, if the source
> > kernel allows (gasp) SG_IO on a partition and the destination
> > does not. So, we can migrate safely even if the source
> > had VIRTIO_BLK_F_SCSI and the destination does not.
> >
> > Signed-off-by: Paolo Bonzini <address@hidden>
>
> My first reaction is you want a new non guest
> visible flag to control whether SG_IO fails on host.
> guest visible ones must be consistent across migration.
So scsi=off/on would control VIRTIO_BLK_F_SCSI, while the new flag would
cause requests to fail. Then it's simpler to do the other way round.
Make the "new non guest-visible flag" be scsi=on/off and set
VIRTIO_BLK_F_SCSI unconditionally as you suggested first.
Paolo
[Qemu-devel] [PATCH 1/3] virtio: let devices be permissive on enabled features, Paolo Bonzini, 2012/03/06