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

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

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