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authorStefano Stabellini <sstabellini@kernel.org>2016-04-15 18:23:00 -0700
committerDavid Vrabel <david.vrabel@citrix.com>2016-05-24 12:58:17 +0100
commitc06b6d70feb32d28f04ba37aa3df17973fd37b6b (patch)
tree90c4513283851eaecb20b7df2b6bcd19770a729d
parentc3b46c73264b03000d1e18b22f5caf63332547c9 (diff)
downloadlinux-c06b6d70feb32d28f04ba37aa3df17973fd37b6b.tar.gz
xen/x86: don't lose event interrupts
On slow platforms with unreliable TSC, such as QEMU emulated machines, it is possible for the kernel to request the next event in the past. In that case, in the current implementation of xen_vcpuop_clockevent, we simply return -ETIME. To be precise the Xen returns -ETIME and we pass it on. However the result of this is a missed event, which simply causes the kernel to hang. Instead it is better to always ask the hypervisor for a timer event, even if the timeout is in the past. That way there are no lost interrupts and the kernel survives. To do that, remove the VCPU_SSHOTTMR_future flag. Signed-off-by: Stefano Stabellini <sstabellini@kernel.org> Acked-by: Juergen Gross <jgross@suse.com>
-rw-r--r--arch/x86/xen/time.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index a0a4e554c6f1..6deba5bc7e34 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -290,11 +290,11 @@ static int xen_vcpuop_set_next_event(unsigned long delta,
WARN_ON(!clockevent_state_oneshot(evt));
single.timeout_abs_ns = get_abs_timeout(delta);
- single.flags = VCPU_SSHOTTMR_future;
+ /* Get an event anyway, even if the timeout is already expired */
+ single.flags = 0;
ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single);
-
- BUG_ON(ret != 0 && ret != -ETIME);
+ BUG_ON(ret != 0);
return ret;
}