Re: [Xen-devel] [PATCH for-4.5] xen/arm: clear UIE on hypervisor entry

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 19 Nov 2014, Konrad Rzeszutek Wilk wrote:
> On Wed, Nov 19, 2014 at 05:44:49PM +0000, Stefano Stabellini wrote:
> > UIE being set can cause maintenance interrupts to occur when Xen writes
> > to one or more LR registers. The effect is a busy loop around the
> > interrupt handler in Xen
> > (http://marc.info/?l=xen-devel&m=141597517132682): everything gets stuck.
> > 
> > Konrad, this fixes an actual bug, at least on OMAP5. It should have no
> > bad side effects on any other platforms as far as I can tell. It should
> > go in 4.5.
> 
> Have you checked (aka ran the tests) on the other platforms?

Yes, I tested on Midway and it runs fine.


> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > Tested-by: Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>
>   ^^^^^^^
>  'Reported-and-Tested-by'

Good point


> > diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> > index 70d10d6..df140b9 100644
> > --- a/xen/arch/arm/gic.c
> > +++ b/xen/arch/arm/gic.c
> > @@ -403,6 +403,8 @@ void gic_clear_lrs(struct vcpu *v)
> >      if ( is_idle_vcpu(v) )
> >          return;
> >  
> > +    gic_hw_ops->update_hcr_status(GICH_HCR_UIE, 0);
> > +
> >      spin_lock_irqsave(&v->arch.vgic.lock, flags);
> >  
> >      while ((i = find_next_bit((const unsigned long *) &this_cpu(lr_mask),
> > @@ -527,8 +529,6 @@ void gic_inject(void)
> >  
> >      if ( !list_empty(&current->arch.vgic.lr_pending) && lr_all_full() )
> >          gic_hw_ops->update_hcr_status(GICH_HCR_UIE, 1);
> > -    else
> > -        gic_hw_ops->update_hcr_status(GICH_HCR_UIE, 0);
> >  }
> >  
> >  static void do_sgi(struct cpu_user_regs *regs, enum gic_sgi sgi)
> 

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