Re: [Xen-devel] [PATCH] xen: arm: vtimer fixes for arm64

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-12-06 at 17:38 +0000, Stefano Stabellini wrote:
> On Thu, 5 Dec 2013, Ian Campbell wrote:
> > @@ -227,12 +242,18 @@ static int vtimer_emulate_sysreg(struct cpu_user_regs 
> > *regs, union hsr hsr)
> >      {
> >      case CNTP_CTL_EL0:
> >          vtimer_cntp_ctl(regs, &r, sysreg.read);
> > -        *x = r;
> > +        if ( sysreg.read )
> > +            *x = r;
> >          return 1;
> >      case CNTP_TVAL_EL0:
> >          vtimer_cntp_tval(regs, &r, sysreg.read);
> > -        *x = r;
> > +        if ( sysreg.read )
> > +            *x = r;
> >          return 1;
> 
> Are you sure that sysreg.read == 1 means write?

On the contrary, it means read.

Here x points to the guest reg that is the target of the read, and r is
the new value which the emulation has produced.

So *x = r is implementing a read from the guest's PoV.

Ian.


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