Tue, Jun 25, 2024 at 04:11:26AM CEST, hengqi@xxxxxxxxxxxxxxxxx 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 On PF only, so far. >this point you think that the device must provide interrupt vectors for it, then >I think this is also true for cvq. I'm working on a fallback where admin queue and cvq would share config vector. Lets see. > >> >> 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 >> > >> >> > >> > >> >> > >> > >> > >> > > >>
