Commit 97254930 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by Jiri Slaby

xen/x86: don't lose event interrupts

commit c06b6d70 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: default avatarStefano Stabellini <sstabellini@kernel.org>
Acked-by: default avatarJuergen Gross <jgross@suse.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
parent bf7a633d
......@@ -362,11 +362,11 @@ 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;
}
......
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