Re: [PATCH] net/mlx5: poll mlx5 eq during irq migration

[Jason Gunthorpe]

On Fri, Mar 06, 2026 at 02:19:09PM +0000, Praveen Kannoju wrote:
> 
> > On Thu, Mar 05, 2026 at 05:08:52PM +0000, Praveen Kannoju wrote:
> >
> > >    Regardless of the underlying causes, which may include IRQ loss
> > >    or EQ re-arming failure, the TX queue becomes stuck, and the
> > >    timeout handler is only triggered once the queue is declared
> > >    full. In scenarios where only specialized packets, such as
> > >    heartbeat packets, are sent through the queue, it takes
> > >    significantly longer for the queue to fill and be identified as
> > >    stuck. A proven solution for this issue is polling the EQ
> > >    immediately after the corresponding IRQ migration, which allows
> > >    for earlier recovery and prevents the transmission queue from
> > >    becoming stuck.
> >
> > I undersand all of this, but for upstreaming we want the root cause, not
> > bodges like this.
> >
> > There is no reason to do what this patch does, the IRQ system is not supposed
> > to loose interrupts on migration, if that is happening on your systems it is a
> > serious bug that must be root caused.
> 
> Thank you, Jason.
> We'll evaluate more on it.

If this is in a VM running under qemu - qemu does Lots Of Stuff
whenever a MSI-X is changed and that stuff has been buggy before and
resulted in lost things.

If it is bare metal, I'm shocked. Maybe an IOMMU driver bug in the
interrupt remapping?

Jason