Zhu, Lingshan
2023-Oct-16 08:33 UTC
[PATCH vfio 10/11] vfio/virtio: Expose admin commands over virtio device
On 10/13/2023 9:50 PM, Michael S. Tsirkin wrote:> On Fri, Oct 13, 2023 at 06:28:34PM +0800, Zhu, Lingshan wrote: >> >> On 10/12/2023 9:27 PM, Jason Gunthorpe wrote: >> >> On Thu, Oct 12, 2023 at 06:29:47PM +0800, Zhu, Lingshan wrote: >> >> >> sorry for the late reply, we have discussed this for weeks in virtio mailing >> list. I have proposed a live migration solution which is a config space solution. >> >> I'm sorry that can't be a serious proposal - config space can't do >> DMA, it is not suitable. >> >> config space only controls the live migration process and config the related >> facilities. >> We don't use config space to transfer data. >> >> The new added registers work like queue_enable or features. >> >> For example, we use DMA to report dirty pages and MMIO to fetch the dirty data. >> >> I remember in another thread you said:"you can't use DMA for any migration >> flows" >> >> And I agree to that statement, so we use config space registers to control the >> flow. >> >> Thanks, >> Zhu Lingshan >> >> >> Jason >> > If you are using dma then I don't see what's wrong with admin vq. > dma is all it does.dma != admin vq, and I think we have discussed many details in pros and cons in admin vq live migration proposal in virtio-comment. I am not sure we should span the discussions here, repeat them over again. Thanks>
Michael S. Tsirkin
2023-Oct-16 08:52 UTC
[PATCH vfio 10/11] vfio/virtio: Expose admin commands over virtio device
On Mon, Oct 16, 2023 at 04:33:10PM +0800, Zhu, Lingshan wrote:> > > On 10/13/2023 9:50 PM, Michael S. Tsirkin wrote: > > On Fri, Oct 13, 2023 at 06:28:34PM +0800, Zhu, Lingshan wrote: > > > > > > On 10/12/2023 9:27 PM, Jason Gunthorpe wrote: > > > > > > On Thu, Oct 12, 2023 at 06:29:47PM +0800, Zhu, Lingshan wrote: > > > > > > > > > sorry for the late reply, we have discussed this for weeks in virtio mailing > > > list. I have proposed a live migration solution which is a config space solution. > > > > > > I'm sorry that can't be a serious proposal - config space can't do > > > DMA, it is not suitable. > > > > > > config space only controls the live migration process and config the related > > > facilities. > > > We don't use config space to transfer data. > > > > > > The new added registers work like queue_enable or features. > > > > > > For example, we use DMA to report dirty pages and MMIO to fetch the dirty data. > > > > > > I remember in another thread you said:"you can't use DMA for any migration > > > flows" > > > > > > And I agree to that statement, so we use config space registers to control the > > > flow. > > > > > > Thanks, > > > Zhu Lingshan > > > > > > > > > Jason > > > > > If you are using dma then I don't see what's wrong with admin vq. > > dma is all it does. > dma != admin vq,Well they share the same issue that they don't work for nesting because DMA can not be intercepted.> and I think we have discussed many details in pros and cons > in admin vq live migration proposal in virtio-comment. > I am not sure we should span the discussions here, repeat them over again. > > Thanks > >Yea let's not. -- MST