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xen: correctly check for pending events when restoring irq flags
In xen_restore_fl_direct(), xen_force_evtchn_callback() was being called even if no events were pending. This resulted in (depending on workload) about a 100 times as many xen_version hypercalls as necessary. Fix this by correcting the sense of the conditional jump. This seems to give a significant performance benefit for some workloads. There is some subtle tricksy "..since the check here is trying to check both pending and masked in a single cmpw, but I think this is correct. It will call check_events now only when the combined mask+pending word is 0x0001 (aka unmasked, pending)." (Ian) CC: stable@kernel.org Acked-by: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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@ -96,7 +96,7 @@ ENTRY(xen_restore_fl_direct)
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/* check for unmasked and pending */
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cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
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jz 1f
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jnz 1f
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2: call check_events
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1:
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ENDPATCH(xen_restore_fl_direct)
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