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authorDavid Vrabel <david.vrabel@citrix.com>2012-04-26 19:44:06 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-05-07 08:56:32 -0700
commitaa4a6ac6d1eec0fb5c88cbc352a056ae826bc985 (patch)
parentd25895e8f1e5e29823d373096d8f3d271bf11821 (diff)
xen: correctly check for pending events when restoring irq flags
commit 7eb7ce4d2e8991aff4ecb71a81949a907ca755ac upstream. 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) 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index 79d7362ad6d1..3e45aa000718 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -96,7 +96,7 @@ ENTRY(xen_restore_fl_direct)
/* check for unmasked and pending */
cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
- jz 1f
+ jnz 1f
2: call check_events