Re: [Xen-devel] [PATCH] xen/x86: don't lose event interrupts
On Thu, Apr 21, 2016 at 02:34:25PM +0100, Stefano Stabellini wrote: > 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 StabelliniThanks, it's now committed: https://svnweb.freebsd.org/base?view=revision=298926 Roger. ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH] xen/x86: don't lose event interrupts
On Thu, 21 Apr 2016, Juergen Gross wrote: > On 16/04/16 03:23, Stefano Stabellini wrote: > > 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 I committed it to xentip/for-linus-4.7 > > diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c > > index a0a4e55..6deba5b 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, ); > > - > > - BUG_ON(ret != 0 && ret != -ETIME); > > + BUG_ON(ret != 0); > > > > return ret; > > } > > > ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
[Xen-devel] [PATCH] xen/x86: don't lose event interrupts
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 Stabellinidiff --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, )); } ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH] xen/x86: don't lose event interrupts
On 16/04/16 03:23, Stefano Stabellini wrote: > 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 StabelliniAcked-by: Juergen Gross > > diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c > index a0a4e55..6deba5b 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, ); > - > - BUG_ON(ret != 0 && ret != -ETIME); > + BUG_ON(ret != 0); > > return ret; > } > ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
[Xen-devel] [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 Stabellinidiff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index a0a4e55..6deba5b 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, ); - - BUG_ON(ret != 0 && ret != -ETIME); + BUG_ON(ret != 0); return ret; } ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel