Re: [Xen-devel] [PATCH v2 5/9] xen: arm: Handle CP15 register traps from userspace

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2015-02-17 at 15:07 +0000, Julien Grall wrote:
> Hi Ian,
> 
> On 10/02/15 04:45, Ian Campbell wrote:
> >      default:
> > @@ -2047,8 +2070,7 @@ asmlinkage void do_trap_hypervisor(struct 
> > cpu_user_regs *regs)
> >          advance_pc(regs, hsr);
> >          break;
> >      case HSR_EC_CP15_32:
> > -        if ( !is_32bit_domain(current->domain) )
> > -            goto bad_trap;
> > +        BUG_ON(!psr_mode_is_32bit(regs->cpsr));
> 
> It's a bit strange that on the previous patch (#5) you fixed CP15_64 but
> not CP15_32. If I'm not mistaken you need both in-order to make the
> things correctly work.

The previous patch (I think you meant #4) made the CP15_64 handlers
correct (since as it happens they are all vtimer related), while it is
only at this point that the cp15_32 registers are all finally updated.

> So, I would invert the 2 patches.

I'm not sure the ordering matters, none of this will be active until the
final patch removes the top-level check. IOW I think the patches make as
much sense in either order and this is the one it has ended up in.

Ian.


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