Re: [PATCH v2 3/7] x86/irq: limit interrupt movement done by fixup_irqs()

["Oleksii K." <oleksii.kurochko@xxxxxxxxx>]

On Tue, 2024-06-11 at 11:59 +0200, Jan Beulich wrote:
> On 10.06.2024 16:20, Roger Pau Monne wrote:
> > The current check used in fixup_irqs() to decide whether to move
> > around
> > interrupts is based on the affinity mask, but such mask can have
> > all bits set,
> > and hence is unlikely to be a subset of the input mask.  For
> > example if an
> > interrupt has an affinity mask of all 1s, any input to fixup_irqs()
> > that's not
> > an all set CPU mask would cause that interrupt to be shuffled
> > around
> > unconditionally.
> > 
> > What fixup_irqs() care about is evacuating interrupts from CPUs not
> > set on the
> > input CPU mask, and for that purpose it should check whether the
> > interrupt is
> > assigned to a CPU not present in the input mask.  Assume that -
> > >arch.cpu_mask
> > is a subset of the ->affinity mask, and keep the current logic that
> > resets the
> > ->affinity mask if the interrupt has to be shuffled around.
> > 
> > Doing the affinity movement based on ->arch.cpu_mask requires
> > removing the
> > special handling to ->arch.cpu_mask done for high priority vectors,
> > otherwise
> > the adjustment done to cpu_mask makes them always skip the CPU
> > interrupt
> > movement.
> > 
> > While there also adjust the comment as to the purpose of
> > fixup_irqs().
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Release-Acked-By: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

~ Oleksii
> 
> Aiui this is independent of patch 1, so could go in while we still
> settle on
> how to word things there?
> 
> Jan
>