Messages in this thread | | | From | Jason Wang <> | Date | Mon, 11 Apr 2022 16:22:19 +0800 | Subject | Re: [PATCH V2 4/5] virtio-pci: implement synchronize_vqs() |
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On Sun, Apr 10, 2022 at 3:51 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Fri, Apr 08, 2022 at 03:03:07PM +0200, Halil Pasic wrote: > > On Wed, 06 Apr 2022 15:04:32 +0200 > > Cornelia Huck <cohuck@redhat.com> wrote: > > > > > On Wed, Apr 06 2022, "Michael S. Tsirkin" <mst@redhat.com> wrote: > > > > > > > On Wed, Apr 06, 2022 at 04:35:37PM +0800, Jason Wang wrote: > > > >> This patch implements PCI version of synchronize_vqs(). > > > >> > > > >> Cc: Thomas Gleixner <tglx@linutronix.de> > > > >> Cc: Peter Zijlstra <peterz@infradead.org> > > > >> Cc: "Paul E. McKenney" <paulmck@kernel.org> > > > >> Cc: Marc Zyngier <maz@kernel.org> > > > >> Signed-off-by: Jason Wang <jasowang@redhat.com> > > > > > > > > Please add implementations at least for ccw and mmio. > > > > > > I'm not sure what (if anything) can/should be done for ccw... > > > > If nothing needs to be done I would like to have at least a comment in > > the code that explains why. So that somebody who reads the code > > doesn't wonder: why is virtio-ccw not implementing that callback. > > Right. > > I am currently thinking instead of making this optional in the > core we should make it mandatory, and have transports which do not > need to sync have an empty stub with documentation explaining why. > > Also, do we want to document this sync is explicitly for irq enable/disable? > synchronize_irq_enable_disable?
I would not since the transport is not guaranteed to use an interrupt for callbacks.
> > > > > > > > > > > > >> --- > > > >> drivers/virtio/virtio_pci_common.c | 14 ++++++++++++++ > > > >> drivers/virtio/virtio_pci_common.h | 2 ++ > > > >> drivers/virtio/virtio_pci_legacy.c | 1 + > > > >> drivers/virtio/virtio_pci_modern.c | 2 ++ > > > >> 4 files changed, 19 insertions(+) > > > >> > > > >> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c > > > >> index d724f676608b..b78c8bc93a97 100644 > > > >> --- a/drivers/virtio/virtio_pci_common.c > > > >> +++ b/drivers/virtio/virtio_pci_common.c > > > >> @@ -37,6 +37,20 @@ void vp_synchronize_vectors(struct virtio_device *vdev) > > > >> synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i)); > > > >> } > > > >> > > > >> +void vp_synchronize_vqs(struct virtio_device *vdev) > > > >> +{ > > > >> + struct virtio_pci_device *vp_dev = to_vp_device(vdev); > > > >> + int i; > > > >> + > > > >> + if (vp_dev->intx_enabled) { > > > >> + synchronize_irq(vp_dev->pci_dev->irq); > > > >> + return; > > > >> + } > > > >> + > > > >> + for (i = 0; i < vp_dev->msix_vectors; ++i) > > > >> + synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i)); > > > >> +} > > > >> + > > > > > > ...given that this seems to synchronize threaded interrupt handlers? > > > Halil, do you think ccw needs to do anything? (AFAICS, we only have one > > > 'irq' for channel devices anyway, and the handler just calls the > > > relevant callbacks directly.) > > > > Sorry I don't understand enough yet. A more verbose documentation on > > "virtio_synchronize_vqs - synchronize with virtqueue callbacks" would > > surely benefit me. It may be more than enough for a back-belt but it > > ain't enough for me to tell what is the callback supposed to accomplish. > > > > I will have to study this discussion and the code more thoroughly. > > Tentatively I side with Jason and Michael in a sense, that I don't > > believe virtio-ccw is safe against rough interrupts.
That's my feeling as well.
Thanks
> > > > Sorry for the late response. I intend to revisit this on Monday. If > > I don't please feel encouraged to ping. > > > > Regards, > > Halil >
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