linux_dsm_epyc7002/drivers/xen
Boris Ostrovsky ff1e22e7a6 xen/events: Mask a moving irq
Moving an unmasked irq may result in irq handler being invoked on both
source and target CPUs.

With 2-level this can happen as follows:

On source CPU:
        evtchn_2l_handle_events() ->
            generic_handle_irq() ->
                handle_edge_irq() ->
                   eoi_pirq():
                       irq_move_irq(data);

                       /***** WE ARE HERE *****/

                       if (VALID_EVTCHN(evtchn))
                           clear_evtchn(evtchn);

If at this moment target processor is handling an unrelated event in
evtchn_2l_handle_events()'s loop it may pick up our event since target's
cpu_evtchn_mask claims that this event belongs to it *and* the event is
unmasked and still pending. At the same time, source CPU will continue
executing its own handle_edge_irq().

With FIFO interrupt the scenario is similar: irq_move_irq() may result
in a EVTCHNOP_unmask hypercall which, in turn, may make the event
pending on the target CPU.

We can avoid this situation by moving and clearing the event while
keeping event masked.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-04-04 11:18:00 +01:00
..
events
xen-pciback
xenbus
xenfs
acpi.c
balloon.c
biomerge.c
cpu_hotplug.c
dbgp.c
efi.c
evtchn.c
fallback.c
features.c
gntalloc.c
gntdev.c
grant-table.c
Kconfig
Makefile
manage.c
mcelog.c
pci.c
pcpu.c
platform-pci.c
preempt.c
privcmd.c
privcmd.h
swiotlb-xen.c
sys-hypervisor.c
time.c
tmem.c
xen-acpi-cpuhotplug.c
xen-acpi-memhotplug.c
xen-acpi-pad.c
xen-acpi-processor.c
xen-balloon.c
xen-scsiback.c
xen-selfballoon.c
xen-stub.c
xlate_mmu.c