Re: [PATCH v3 0/3] x86/irq: fixes for CPU hot{,un}plug

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

On Fri, 2024-06-14 at 09:28 +0200, Roger Pau Monné wrote:
> Sorry, forgot to add the for-4.19 tag and Cc Oleksii.
> 
> Since we have taken the start of the series, we might as well take
> the
> remaining patches (if other x86 maintainers agree) and attempt to
> hopefully fix all the interrupt issues with CPU hotplug/unplug.
> 
> FTR: there are further issues when doing CPU hotplug/unplug from a
> PVH
> dom0, but those are out of the scope for 4.19, as I haven't even
> started to diagnose what's going on.
And this issues were before the current patch series was introduced?

~ Oleksii
> 
> Thanks, Roger.
> 
> On Thu, Jun 13, 2024 at 06:56:14PM +0200, Roger Pau Monne wrote:
> > Hello,
> > 
> > The following series aim to fix interrupt handling when doing CPU
> > plug/unplug operations.  Without this series running:
> > 
> > cpus=`xl info max_cpu_id`
> > while [ 1 ]; do
> >     for i in `seq 1 $cpus`; do
> >         xen-hptool cpu-offline $i;
> >         xen-hptool cpu-online $i;
> >     done
> > done
> > 
> > Quite quickly results in interrupts getting lost and "No irq
> > handler for
> > vector" messages on the Xen console.  Drivers in dom0 also start
> > getting
> > interrupt timeouts and the system becomes unusable.
> > 
> > After applying the series running the loop over night still result
> > in a
> > fully usable system, no  "No irq handler for vector" messages at
> > all, no
> > interrupt loses reported by dom0.  Test with x2apic-
> > mode={mixed,cluster}.
> > 
> > I've attempted to document all code as good as I could, interrupt
> > handling has some unexpected corner cases that are hard to diagnose
> > and
> > reason about.
> > 
> > Some XenRT testing is undergoing to ensure no breakages.
> > 
> > Thanks, Roger.
> > 
> > Roger Pau Monne (3):
> >   x86/irq: deal with old_cpu_mask for interrupts in movement in
> >     fixup_irqs()
> >   x86/irq: handle moving interrupts in _assign_irq_vector()
> >   x86/irq: forward pending interrupts to new destination in
> > fixup_irqs()
> > 
> >  xen/arch/x86/include/asm/apic.h |   5 +
> >  xen/arch/x86/irq.c              | 163 +++++++++++++++++++++++++---
> > ----
> >  2 files changed, 132 insertions(+), 36 deletions(-)
> > 
> > -- 
> > 2.45.2
> >