On Tue, Jun 25, 2024 at 10:11:26AM +0800, Heng Qi wrote: > On Mon, 24 Jun 2024 11:16:45 -0400, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > On Mon, Jun 24, 2024 at 04:51:37PM +0200, Jiri Pirko wrote: > > > Mon, Jun 24, 2024 at 03:55:53PM CEST, mst@xxxxxxxxxx wrote: > > > >On Mon, Jun 24, 2024 at 03:46:19PM +0200, Jiri Pirko wrote: > > > >> Mon, Jun 24, 2024 at 01:23:01PM CEST, mst@xxxxxxxxxx wrote: > > > >> >On Mon, Jun 24, 2024 at 05:53:52PM +0800, Heng Qi wrote: > > > >> >> On Mon, 24 Jun 2024 11:04:43 +0200, Jiri Pirko <jiri@xxxxxxxxxxx> wrote: > > > >> >> > From: Jiri Pirko <jiri@xxxxxxxxxx> > > > >> >> > > > > >> >> > Currently the admin queue command execution is serialized by a lock. > > > >> >> > This patchsets lifts this limitation allowing to execute admin queue > > > >> >> > commands in parallel. To do that, admin queue processing needs to be > > > >> >> > converted from polling to interrupt based completion. > > > >> >> > > > > >> >> > Patches #1-#6 are preparations, making things a bit smoother as well. > > > >> >> > Patch #7 implements interrupt based completion for admin queue. > > > >> >> > > > >> >> Hi, Jiri > > > >> >> > > > >> >> Before this set, I pushed the cvq irq set [1], and the discussion focused on the > > > >> >> fact that the newly added irq vector may cause the IO queue to fall back to > > > >> >> shared interrupt mode. > > > >> >> But it is true that devices implemented according to the specification should > > > >> >> not encounter this problem. So what do you think? > > > >> > > > >> Wait. Please note that admin queue is only created and used by PF virtio > > > >> device. And most probably, this is on hypervisor managing the VFs that > > > >> are passed to guest VMs. These VFs does not have admin queue. > > > >> > > > >> Therefore, this is hardly comparable to control vq. > > > > > > > > > > > >Well Parav recently posted patches adding admin queue > > > >to VFs, with new "self" group type. > > > > > > Right, but even so, when device implementation decides to implement and > > > enable admin queue, it should also make sure to provide correct amount > > > of vectors. My point is, there should not be any breakage in user > > > expectation, or am I missing something? > > > > > > Hmm, I think you are right that cvq is an existing capability > > and adminq is newer. > > admin vq has been supported in the kernel for more than half a year, and if at > this point you think that the device must provide interrupt vectors for it, then > I think this is also true for cvq. There's a big difference between 15 years and half a year. I don't think any hardware devices have been released with the capability just yet, and yes allocating a vector for each queue is a good idea for hardware devices. > > > > Gimme a couple of days to think all this over, hopefully we'll also see > > a new version of the cvq patch, making it easier to see whether they > > interact and if so, how. > > > > > > > > > > > > > > > > > > > > >> > > > >> >> > > > >> >> [1] https://lore.kernel.org/all/20240619171708-mutt-send-email-mst@xxxxxxxxxx/ > > > >> > > > > >> >It's true - this can cause guest to run out of vectors for a variety of > > > >> >reasons. > > > >> > > > > >> >First we have guest irqs - I am guessing avq could use IRQF_SHARED ? > > > >> > > > >> There is no avq in quest, under normal circumstances. Unless for some > > > >> reason somebody passes trough virtio PF into guest. > > > > > > > > > > > >At the moment, but this will change soon. > > > > > > > > > > > >> > > > >> >I am not sure why we don't allow IRQF_SHARED for the config > > > >> >interrupt though. So I think addressing this part can be deferred. > > > >> > > > > >> >Second, we might not have enough msix vectors on the device. Here sharing > > > >> >with e.g. cvq and further with config interrupt would make sense. > > > >> > > > >> For cvq irq vector, I believe that sharing with config irq makes sense. > > > >> Even for admin queue maybe. But again, admin queue is on PF. I don't > > > >> think this is a real concern. > > > >> > > > >> > > > >> > > > > >> >Jiri do you think you can help Heng Qi hammer out a solution for cvq? > > > >> >I feel this will work will then benefit in a similar way, > > > >> >and having us poll aggressively for cvq but not admin commands > > > >> >does not make much sense, right? > > > >> > > > > >> >> > Patch #8 finally removes the admin queue serialization lock. > > > >> >> > > > > >> >> > Jiri Pirko (8): > > > >> >> > virtio_pci: push out single vq find code to vp_find_one_vq_msix() > > > >> >> > virtio_pci_modern: treat vp_dev->admin_vq.info.vq pointer as static > > > >> >> > virtio: push out code to vp_avq_index() > > > >> >> > virtio: create admin queues alongside other virtqueues > > > >> >> > virtio_pci_modern: create admin queue of queried size > > > >> >> > virtio_pci_modern: pass cmd as an identification token > > > >> >> > virtio_pci_modern: use completion instead of busy loop to wait on > > > >> >> > admin cmd result > > > >> >> > virtio_pci_modern: remove admin queue serialization lock > > > >> >> > > > > >> >> > drivers/virtio/virtio.c | 28 +---- > > > >> >> > drivers/virtio/virtio_pci_common.c | 109 ++++++++++++++------ > > > >> >> > drivers/virtio/virtio_pci_common.h | 9 +- > > > >> >> > drivers/virtio/virtio_pci_modern.c | 160 ++++++++++++----------------- > > > >> >> > include/linux/virtio.h | 2 + > > > >> >> > include/linux/virtio_config.h | 2 - > > > >> >> > 6 files changed, 150 insertions(+), 160 deletions(-) > > > >> >> > > > > >> >> > -- > > > >> >> > 2.45.1 > > > >> >> > > > > >> >> > > > > >> > > > > > > >
