Subject: [PATCH 2/5] ARM: KVM: add missing dsb before invalidating Stage-2 TLBs

From: [email-masked] (Christoffer Dall)
Date: Wed, 19 Jun 2013 17:08:59 -0700

On Wed, Jun 19, 2013 at 05:05:22PM -0700, Christoffer Dall wrote:
> On Wed, Jun 19, 2013 at 02:20:03PM +0100, Marc Zyngier wrote:
> > When performing a Stage-2 TLB invalidation, it is necessary to
> > make sure the write to the page tables is observable by all CPUs.
> > 
> > For this purpose, add a dsb instruction to __kvm_tlb_flush_vmid_ipa
> > before doing the TLB invalidation itself.
> > 
> > Signed-off-by: Marc Zyngier <[email-masked]>
> > ---
> >  arch/arm/kvm/interrupts.S | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> > index d0a8fa3..afa6c04 100644
> > --- a/arch/arm/kvm/interrupts.S
> > +++ b/arch/arm/kvm/interrupts.S
> > @@ -49,6 +49,7 @@ __kvm_hyp_code_start:
> >  ENTRY(__kvm_tlb_flush_vmid_ipa)
> >  	push	{r2, r3}
> >  
> > +	dsb
> 
> shouldn't this be a dmb then?
> 
> thinking that a dsb only ensures completion between load/stores and not
> between the preceeding store and the actual invalidate operation?
> 
> or are we relying on the fact that the store must complete before the
> ldrd below, which must happen before the mcrr, which must happen before
> the invalidate (?), and therefore it's all good?
> 

bah, ignore my crazy rambling, I completely switched the two when I read
the definitions.

> >  	add	r0, r0, #KVM_VTTBR
> >  	ldrd	r2, r3, [r0]
> >  	mcrr	p15, 6, r2, r3, c2	@ Write VTTBR
> > -- 
> > 1.8.2.3
> > 
> > 
> > 
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