Check whether the emulated device is actually enabled before trying to
resume the associated timers.

Thankfully all those structures are zeroed at initialization, and
since the devices are not enabled they are never populated, which
triggers the pt->vcpu check at the beginning of pt_resume forcing an
exit from the function.

While there limit the scope of i and make it unsigned.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/hvm/vpt.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/hvm/vpt.c b/xen/arch/x86/hvm/vpt.c
index 47f2c2aa64..62c87867c5 100644
--- a/xen/arch/x86/hvm/vpt.c
+++ b/xen/arch/x86/hvm/vpt.c
@@ -636,14 +636,19 @@ static void pt_resume(struct periodic_time *pt)
 
 void pt_may_unmask_irq(struct domain *d, struct periodic_time *vlapic_pt)
 {
-    int i;
-
     if ( d )
     {
-        pt_resume(&d->arch.vpit.pt0);
-        pt_resume(&d->arch.hvm.pl_time->vrtc.pt);
-        for ( i = 0; i < HPET_TIMER_NUM; i++ )
-            pt_resume(&d->arch.hvm.pl_time->vhpet.pt[i]);
+        if ( has_vpit(d) )
+            pt_resume(&d->arch.vpit.pt0);
+        if ( has_vrtc(d) )
+            pt_resume(&d->arch.hvm.pl_time->vrtc.pt);
+        if ( has_vhpet(d) )
+        {
+            unsigned int i;
+
+            for ( i = 0; i < HPET_TIMER_NUM; i++ )
+                pt_resume(&d->arch.hvm.pl_time->vhpet.pt[i]);
+        }
     }
 
     if ( vlapic_pt )
-- 
2.26.2

On 12.06.2020 17:56, Roger Pau Monne wrote:
> Check whether the emulated device is actually enabled before trying to
> resume the associated timers.
> 
> Thankfully all those structures are zeroed at initialization, and
> since the devices are not enabled they are never populated, which
> triggers the pt->vcpu check at the beginning of pt_resume forcing an
> exit from the function.

So really this is a benign transformation then, rather than fixing
anything? If that's correct understanding of mine ...

> While there limit the scope of i and make it unsigned.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

Jan

On Thu, Jun 18, 2020 at 04:37:57PM +0200, Jan Beulich wrote:
> On 12.06.2020 17:56, Roger Pau Monne wrote:
> > Check whether the emulated device is actually enabled before trying to
> > resume the associated timers.
> > 
> > Thankfully all those structures are zeroed at initialization, and
> > since the devices are not enabled they are never populated, which
> > triggers the pt->vcpu check at the beginning of pt_resume forcing an
> > exit from the function.
> 
> So really this is a benign transformation then, rather than fixing
> anything? If that's correct understanding of mine ...

Yes, that's my understanding also.

> > While there limit the scope of i and make it unsigned.
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@suse.com>

Thanks, Roger.