On Thu, Feb 27, 2020 at 05:53:32PM +0100, Auger Eric wrote:
> Hi Peter,
>
> On 2/26/20 11:50 PM, Peter Xu wrote:
> > It's currently broken. Let's use the slow path to at least make it
> > functional.
> >
> > Signed-off-by: Peter Xu <peterx@redhat.com>
>
> > ---
> > hw/vfio/pci.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> > index 5e75a95129..98e0e0c994 100644
> > --- a/hw/vfio/pci.c
> > +++ b/hw/vfio/pci.c
> > @@ -128,6 +128,18 @@ static void vfio_intx_enable_kvm(VFIOPCIDevice *vdev, Error **errp)
> > return;
> > }
> >
> > + if (kvm_irqchip_is_split()) {
> > + /*
> > + * VFIO INTx is currently not working with split kernel
> > + * irqchip for level triggered interrupts. Go the slow path
> > + * as long as split is enabled so we can be at least
> > + * functional (even with poor performance).
> > + *
> > + * TODO: Remove this after all things fixed up.
> If this patch were to be applied sooner than the other patches as
> suggested in the cover letter, We may emit a warning message saying that
> slow path is selected due to split irqchip and this will induce perf
> downgrade
Yes we can. Here I followed the rest of the cases where we'll
silently fallback to slow path if e.g. we used an even older kernel
that does not support resamplefd at all. IMHO it's the same as that
(feature not supported yet, silent fallback, just in case it scares
the user a bit, which makes some sense).
> > + */
> > + return;
> > + }
> > +
> > /* Get to a known interrupt state */
> > qemu_set_fd_handler(irqfd.fd, NULL, NULL, vdev);
> > vfio_mask_single_irqindex(&vdev->vbasedev, VFIO_PCI_INTX_IRQ_INDEX);
> >
>
>
> Tested with a 5.2-rc1 kernel with reverted "654f1f13ea56 kvm: Check
> irqchip mode before assign irqfd" and guest booting with nomsi.
>
> Without this patch the assigned NIC does not work. This patch fixes the
> issue.
>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Tested-by: Eric Auger <eric.auger@redhat.com>
Thanks Eric!
--
Peter Xu