Stefano Garzarella
2023-Jun-05 13:30 UTC
[PATCH] vhost-vdpa: filter VIRTIO_F_RING_PACKED feature
On Mon, Jun 05, 2023 at 09:00:25AM -0400, Michael S. Tsirkin wrote:>On Mon, Jun 05, 2023 at 02:54:20PM +0200, Stefano Garzarella wrote: >> On Mon, Jun 05, 2023 at 08:41:54AM -0400, Michael S. Tsirkin wrote: >> > On Mon, Jun 05, 2023 at 01:06:44PM +0200, Stefano Garzarella wrote: >> > > vhost-vdpa IOCTLs (eg. VHOST_GET_VRING_BASE, VHOST_SET_VRING_BASE) >> > > don't support packed virtqueue well yet, so let's filter the >> > > VIRTIO_F_RING_PACKED feature for now in vhost_vdpa_get_features(). >> > > >> > > This way, even if the device supports it, we don't risk it being >> > > negotiated, then the VMM is unable to set the vring state properly. >> > > >> > > Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend") >> > > Cc: stable at vger.kernel.org >> > > Signed-off-by: Stefano Garzarella <sgarzare at redhat.com> >> > > --- >> > > >> > > Notes: >> > > This patch should be applied before the "[PATCH v2 0/3] vhost_vdpa: >> > > better PACKED support" series [1] and backported in stable branches. >> > > >> > > We can revert it when we are sure that everything is working with >> > > packed virtqueues. >> > > >> > > Thanks, >> > > Stefano >> > > >> > > [1] https://lore.kernel.org/virtualization/20230424225031.18947-1-shannon.nelson at amd.com/ >> > >> > I'm a bit lost here. So why am I merging "better PACKED support" then? >> >> To really support packed virtqueue with vhost-vdpa, at that point we would >> also have to revert this patch. >> >> I wasn't sure if you wanted to queue the series for this merge window. >> In that case do you think it is better to send this patch only for stable >> branches? >> > Does this patch make them a NOP? >> >> Yep, after applying the "better PACKED support" series and being sure >> that >> the IOCTLs of vhost-vdpa support packed virtqueue, we should revert this >> patch. >> >> Let me know if you prefer a different approach. >> >> I'm concerned that QEMU uses vhost-vdpa IOCTLs thinking that the kernel >> interprets them the right way, when it does not. >> >> Thanks, >> Stefano >> > >If this fixes a bug can you add Fixes tags to each of them? Then it's ok >to merge in this window. Probably easier than the elaborate >mask/unmask dance.CCing Shannon (the original author of the "better PACKED support" series). IIUC Shannon is going to send a v3 of that series to fix the documentation, so Shannon can you also add the Fixes tags? Thanks, Stefano
Michael S. Tsirkin
2023-Jun-05 13:54 UTC
[PATCH] vhost-vdpa: filter VIRTIO_F_RING_PACKED feature
On Mon, Jun 05, 2023 at 03:30:35PM +0200, Stefano Garzarella wrote:> On Mon, Jun 05, 2023 at 09:00:25AM -0400, Michael S. Tsirkin wrote: > > On Mon, Jun 05, 2023 at 02:54:20PM +0200, Stefano Garzarella wrote: > > > On Mon, Jun 05, 2023 at 08:41:54AM -0400, Michael S. Tsirkin wrote: > > > > On Mon, Jun 05, 2023 at 01:06:44PM +0200, Stefano Garzarella wrote: > > > > > vhost-vdpa IOCTLs (eg. VHOST_GET_VRING_BASE, VHOST_SET_VRING_BASE) > > > > > don't support packed virtqueue well yet, so let's filter the > > > > > VIRTIO_F_RING_PACKED feature for now in vhost_vdpa_get_features(). > > > > > > > > > > This way, even if the device supports it, we don't risk it being > > > > > negotiated, then the VMM is unable to set the vring state properly. > > > > > > > > > > Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend") > > > > > Cc: stable at vger.kernel.org > > > > > Signed-off-by: Stefano Garzarella <sgarzare at redhat.com> > > > > > --- > > > > > > > > > > Notes: > > > > > This patch should be applied before the "[PATCH v2 0/3] vhost_vdpa: > > > > > better PACKED support" series [1] and backported in stable branches. > > > > > > > > > > We can revert it when we are sure that everything is working with > > > > > packed virtqueues. > > > > > > > > > > Thanks, > > > > > Stefano > > > > > > > > > > [1] https://lore.kernel.org/virtualization/20230424225031.18947-1-shannon.nelson at amd.com/ > > > > > > > > I'm a bit lost here. So why am I merging "better PACKED support" then? > > > > > > To really support packed virtqueue with vhost-vdpa, at that point we would > > > also have to revert this patch. > > > > > > I wasn't sure if you wanted to queue the series for this merge window. > > > In that case do you think it is better to send this patch only for stable > > > branches? > > > > Does this patch make them a NOP? > > > > > > Yep, after applying the "better PACKED support" series and being > > > sure that > > > the IOCTLs of vhost-vdpa support packed virtqueue, we should revert this > > > patch. > > > > > > Let me know if you prefer a different approach. > > > > > > I'm concerned that QEMU uses vhost-vdpa IOCTLs thinking that the kernel > > > interprets them the right way, when it does not. > > > > > > Thanks, > > > Stefano > > > > > > > If this fixes a bug can you add Fixes tags to each of them? Then it's ok > > to merge in this window. Probably easier than the elaborate > > mask/unmask dance. > > CCing Shannon (the original author of the "better PACKED support" > series). > > IIUC Shannon is going to send a v3 of that series to fix the > documentation, so Shannon can you also add the Fixes tags? > > Thanks, > StefanoWell this is in my tree already. Just reply with Fixes: <> to each and I will add these tags. If I start dropping and rebasing this won't make it in this window. -- MST