Re: [RFC 0/2] disable the configuration interrupt for the unsupported device

[Jason Wang]

Hi Cindy:

On Wed, Mar 27, 2024 at 9:29 AM Cindy Lu <lulu@redhat.com> wrote:
>
> we need a crash in Non-standard image, here is the jira for this 
> https://issues.redhat.com/browse/RHEL-28522
> The root cause of the issue is that an IRQFD was used without initialization..
>
> During the booting process of the Vyatta image, the behavior of the called 
> function in qemu is as follows:
>
> 1. vhost_net_stop() was called, this will call the function
> virtio_pci_set_guest_notifiers() with assgin= false, and
> virtio_pci_set_guest_notifiers(） will release the irqfd for vector 0

Before vhost_net_stop(), do we know which vector is used by which queue?

>
> 2. virtio_reset() was called -->set configure vector to VIRTIO_NO_VECTORt
>
> 3.vhost_net_start() was called (at this time the configure vector is
> still VIRTIO_NO_VECTOR) and call virtio_pci_set_guest_notifiers() with
> assgin= true, so the irqfd for vector 0 was not "init" during this process

How does the configure vector differ from the virtqueue vector here?

>
> 4. The system continues to boot and msix_fire_vector_notifier() was
> called unmask the vector 0 and then met the crash
> [msix_fire_vector_notifier] 112 called vector 0 is_masked 1
> [msix_fire_vector_notifier] 112 called vector 0 is_masked 0
>
> The reason for not reproducing in RHEL/fedora guest image is because
> REHL/Fedora doesn't have the behavior of calling vhost_net_stop and then 
> virtio_reset, and also won't call msix_fire_vector_notifier for vector 0 
> during system boot.
>
> The reason for not reproducing before configure interrupt support is because
> vector 0 is for configure interrupt,  before the support for configure 
> interrupts, the notifier process will not handle vector 0.
>
> For the device Vyatta using, it doesn't support configure interrupts at all, 
> So we plan to disable the configure interrupts in unsupported device

Btw, let's tweak the changelog, it's a little bit hard to understand.

Thanks

>
> Signed-off-by: Cindy Lu <lulu@redhat.com>
>
> Cindy Lu (2):
>   virtio-net: disable the configure interrupt for not support device
>   virtio-pci: check if the configure interrupt enable
>
>  hw/net/virtio-net.c        |  5 ++++-
>  hw/virtio/virtio-pci.c     | 41 +++++++++++++++++++++-----------------
>  hw/virtio/virtio.c         |  1 +
>  include/hw/virtio/virtio.h |  1 +
>  4 files changed, 29 insertions(+), 19 deletions(-)
>
> --
> 2.43.0
>