Date: Thu, 21 Apr 2016 14:34:25 +0100 (BST) From: Stefano Stabellini <sstabellini@kernel.org> To: freebsd-xen@freebsd.org Cc: xen-devel@lists.xenproject.org, sstabellini@kernel.org, roger.pau@citrix.com Subject: [PATCH] xen/x86: don't lose event interrupts Message-ID: <alpine.DEB.2.10.1604211432440.23110@sstabellini-ThinkPad-X260>
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xen/x86: don't lose event interrupts On slow platforms with unreliable TSC, such as QEMU emulated machines, it is possible for the FreeBSD kernel to request the next event in the past. In that case, in the current implementation of xentimer_vcpu_start_timer, we simply return -ETIME. To be precise Xen returns -ETIME and we pass it on. As a consequence we need to loop around to function to make sure that the timer is properly set. Instead it is better to always ask the hypervisor for a timer event, even if the timeout is past. To do that, remove the VCPU_SSHOTTMR_future flag. Signed-off-by: Stefano Stabellini <sstabellini@kernel.org> diff --git a/sys/dev/xen/timer/timer.c b/sys/dev/xen/timer/timer.c index 53aff0a..db9b19b 100644 --- a/sys/dev/xen/timer/timer.c +++ b/sys/dev/xen/timer/timer.c @@ -267,7 +267,8 @@ xentimer_vcpu_start_timer(int vcpu, uint64_t next_time) struct vcpu_set_singleshot_timer single; single.timeout_abs_ns = next_time; - single.flags = VCPU_SSHOTTMR_future; + /* Get an event anyway, even if the timeout is already expired */ + single.flags = 0; return (HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, vcpu, &single)); }
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