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[Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage |
Date: |
Tue, 29 Sep 2009 19:31:24 +0200 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Tue, Sep 29, 2009 at 12:26:13PM -0500, Anthony Liguori wrote:
> Michael S. Tsirkin wrote:
>> On Tue, Sep 29, 2009 at 09:14:56AM -0500, Anthony Liguori wrote:
>>
>>> Michael S. Tsirkin wrote:
>>>
>>>> I don't think it's such a good idea. We want to keep exposing most of
>>>> config space in i/o bar because of backwards compatibility. And we want
>>>> to keep datapath operations such as vq kicks, in i/o space.
>>>>
>>> We can do feature negotiation in virtio-pci. That lets us continue
>>> exposing the first 246 bytes of the config space in PIO and guests
>>> can negotiate a second bar for access to larger config spaces.
>>>
>>> Regards,
>>>
>>> Anthony Liguori
>>>
>>
>> guests can't negotiate a bar.
>>
>
> The host always exposes the config in two places. config[0..235] in
> bytes 20-255 in BAR0 and the full config space in BAR2 (or BAR1 + offset
> if desired). Old drivers will just ignore the new config location.
>
>> What I think we want to do
>> - Use i/o for small fields (2-4 bytes) as we did previously
>> we won't run out anytime soon
>> - For large fields, put them in memory BAR1 and report the
>> offset in i/o space
>>
>
> This is at best a band aid as a large number of small fields can result
> in the same problem.
It would have to be very large :)
>> - For huge fields, provide a mailbox in i/o space where guest
>> writes an offset and reads out a value
>>
>
> Regards,
>
> Anthony Liguori
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, (continued)
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Michael S. Tsirkin, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Avi Kivity, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Michael S. Tsirkin, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Avi Kivity, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Anthony Liguori, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Michael S. Tsirkin, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Anthony Liguori, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Avi Kivity, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Michael S. Tsirkin, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Anthony Liguori, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage,
Michael S. Tsirkin <=
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Rusty Russell, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Anthony Liguori, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Rusty Russell, 2009/09/29
- Re: [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Jamie Lokier, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, john cooper, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Anthony Liguori, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Rusty Russell, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Anthony Liguori, 2009/09/29
- [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Rusty Russell, 2009/09/30
- Re: [Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage, Jamie Lokier, 2009/09/30