From 1e46601d54d1649e4cea55790f8ad2c64e7f94d5 Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Fri, 15 Apr 2016 18:23:00 -0700 Subject: [PATCH] xen/x86: don't lose event interrupts commit c06b6d70feb32d28f04ba37aa3df17973fd37b6b upstream. 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 Acked-by: Juergen Gross Cc: Julia Lawall Signed-off-by: Jiri Slaby Signed-off-by: Willy Tarreau --- arch/x86/xen/time.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index 13e8935e2eab..e3600eb618c1 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -338,11 +338,11 @@ static int xen_vcpuop_set_next_event(unsigned long delta, WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT); 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; } -- 2.20.1