Re: [Xen-devel] [PATCH v6 13/19] x86/VPMU: Handle PMU interrupts for PV guests

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 05/22/2014 11:30 AM, Jan Beulich wrote:
> > @@ -99,14 +120,87 @@ int vpmu_do_rdmsr(unsigned int msr, uint64_t *msr_content)
> >           return 0;
> >   
> >       if ( vpmu->arch_vpmu_ops && vpmu->arch_vpmu_ops->do_rdmsr )
> > -        return vpmu->arch_vpmu_ops->do_rdmsr(msr, msr_content);
> > +    {
> > +        int ret = vpmu->arch_vpmu_ops->do_rdmsr(msr, msr_content);
> > +
> > +        if ( !is_hvm_domain(current->domain) &&
> > +            (current->arch.vpmu.xenpmu_data->pmu_flags & PMU_CACHED) )
> Wouldn't the same comment as in WRMSR handling apply here too?
> If so, either replicate it or add a brief comment referring to the
> other one.

Yes, the comment is applicable here too and the next patch merges the 
two routines.

> > +        /* Store appropriate registers in xenpmu_data */
> > +        if ( is_pv_32bit_domain(current->domain) )
> > +        {
> > +            /*
> > +             * 32-bit dom0 cannot process Xen's addresses (which are 64 bit)
> > +             * and therefore we treat it the same way as a non-priviledged
> > +             * PV 32-bit domain.
> > +             */
> > +            struct compat_cpu_user_regs *cmp;
> > +
> > +            gregs = guest_cpu_user_regs();
> > +
> > +            cmp = (void *)&v->arch.vpmu.xenpmu_data->pmu.r.regs;
> > +            XLAT_cpu_user_regs(cmp, gregs);
> > +            memcpy(&v->arch.vpmu.xenpmu_data->pmu.r.regs,
> > +                   &cmp, sizeof(struct compat_cpu_user_regs));
> Afaict this memcpy() does nothing (src == dst).
Yes, memcpy is unnecessary here, copying is already done by the 
preceeding XLAT_cpu_user_reg().

-boris

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