xen/events: use virt_xxx barriers
drivers/xen/events/events_fifo.c uses rmb() to communicate with the other side. For guests compiled with CONFIG_SMP, smp_rmb would be sufficient, so rmb() here is only needed if a non-SMP guest runs on an SMP host. Switch to the virt_rmb barrier which serves this exact purpose. Pull in asm/barrier.h here to make sure the file is self-contained. Suggested-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: David Vrabel <david.vrabel@citrix.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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@ -41,6 +41,7 @@
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#include <linux/percpu.h>
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#include <linux/cpu.h>
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#include <asm/barrier.h>
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#include <asm/sync_bitops.h>
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#include <asm/xen/hypercall.h>
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#include <asm/xen/hypervisor.h>
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@ -296,7 +297,7 @@ static void consume_one_event(unsigned cpu,
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* control block.
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*/
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if (head == 0) {
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rmb(); /* Ensure word is up-to-date before reading head. */
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virt_rmb(); /* Ensure word is up-to-date before reading head. */
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head = control_block->head[priority];
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}
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