From 9503599d792cc2ec3e512d6b9437da2726012bf9 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 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 (cherry picked from commit c06b6d70feb32d28f04ba37aa3df17973fd37b6b) Signed-off-by: Konrad Rzeszutek Wilk OraBug: 23527575 - UEK4 can't run under Xen nested virtualization --- 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 090243ccab3e..11d2f09bdc28 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -309,11 +309,11 @@ 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; } -- 2.50.1