There is a vector setup race, which overwrites the interrupt
descriptor in the per CPU vector array resulting in a disfunctional device.

CPU0				CPU1
				interrupt is raised in APIC IRR
				but not handled
  free_irq()
    per_cpu(vector_irq, CPU1)[vector] = VECTOR_SHUTDOWN;

  request_irq()			common_interrupt()
  				  d = this_cpu_read(vector_irq[vector]);

    per_cpu(vector_irq, CPU1)[vector] = desc;

    				  if (d == VECTOR_SHUTDOWN)
				    this_cpu_write(vector_irq[vector], VECTOR_UNUSED);

free_irq() cannot observe the pending vector in the CPU1 APIC as there is
no way to query the remote CPUs APIC IRR.

This requires that request_irq() uses the same vector/CPU as the one which
was freed, but this also can be triggered by a spurious interrupt.

Interestingly enough this problem managed to be hidden for more than a
decade.

Prevent this by reevaluating vector_irq under the vector lock, which is
held by the interrupt activation code when vector_irq is updated.

The first patch provides context for subsequent real bugfix patch.

Fixes: 9345005f4eed ("x86/irq: Fix do_IRQ() interrupt warning for cpu hotplug retriggered irqs")
Cc: stable@vger.kernel.org#5.15.x
Cc: gregkh@linuxfoundation.org

v1 -> RESEND
- Add upstream commit ID.

Jacob Pan (1):
  x86/irq: Factor out handler invocation from common_interrupt()

Thomas Gleixner (1):
  x86/irq: Plug vector setup race

 arch/x86/kernel/irq.c | 70 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 56 insertions(+), 14 deletions(-)

-- 
2.34.1