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Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0 |
Date: |
Wed, 15 Jul 2015 11:11:18 +0200 |
On Wed, 15 Jul 2015 13:29:56 +0800
Jason Wang <address@hidden> wrote:
> Hi all:
>
> This series tries to set feature correctly for virtio-blk when virtio
> 1.0 is supported. Two isssues were addressed according to the spec:
>
> - scsi passthrough was not support in 1.0. This is done by, 1) disable
> scsi by defautl for 2.4 machine type and fail the initialization
> when both scsi and 1.0 were set.
> - any layout must be set for transitional device. This is done by set
> any layout when 1.0 is supported.
>
> Please review
>
> Changes from V1:
> - Split virtio-net changes out of the series
> - Enable VIRTIO_BLK_F_SCSI only when scsi is set
> - Disable scsi by default and compat it for legacy machine types
> - Let get_features() can fail and fail the initialization of
> virito-blk when both 1.0 and scsi were supported.
Hm, this seems confusing to me mainly due to the different way
transitional devices are handled by pci and ccw.
For virtio-pci: (please correct me if I misunderstood)
- devices (except input) are transitional by default
- user can disable legacy or modern support
- drivers can use method they prefer, depending on VERSION_1
For virtio-ccw:
- transitional means "in limbo" regarding legacy or modern
- devices become legacy if features are read without negotiation of a
revision, or if revision 0 is negotiated
- they become modern if revision 1 is negotiated
That implies that for ccw, a transitional device does not offer any
features: It either transitions to the legacy or modern state if a
revision was negotiated, or it becomes a legacy device by reading
features (which are the legacy features, then). While pci has "real"
transitional devices needing to offer a certain feature set.
I'm not sure what the solution is here: basically, ccw needs a dynamic
feature set, while pci does not.
- Re: [Qemu-devel] [PATCH V2 2/5] virtio-blk: advertise scsi only when scsi is set, (continued)
[Qemu-devel] [PATCH V2 3/5] virtio-blk: disable scsi passthrough by default, Jason Wang, 2015/07/15
[Qemu-devel] [PATCH V2 4/5] virtio-blk: fail the init when both 1.0 and scsi is set, Jason Wang, 2015/07/15
[Qemu-devel] [PATCH V2 5/5] virtio-blk: set VIRTIO_F_ANY_LAYOUT when 1.0 is supported, Jason Wang, 2015/07/15
Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0,
Cornelia Huck <=
- Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0, Jason Wang, 2015/07/15
- Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0, Cornelia Huck, 2015/07/15
- Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0, Michael S. Tsirkin, 2015/07/15
- Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0, Cornelia Huck, 2015/07/15
- Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0, Michael S. Tsirkin, 2015/07/15
- Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0, Cornelia Huck, 2015/07/15
Re: [Qemu-devel] [PATCH V2 0/5] Set correct blk feature for virtio 1.0, Michael S. Tsirkin, 2015/07/15