Re: [RFC v2 5/6] xen/arm: Implement hypercall for dirty page tracing

[Julien Grall <julien.grall@linaro.org>]

Hi Wei,

On 04/15/2014 10:05 PM, Wei Huang wrote:
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index 3f04a77..d2531ed 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -207,6 +207,12 @@ static void ctxt_switch_to(struct vcpu *n)
>  
>      isb();
>  
> +    /* Dirty-page tracing
> +     * NB: How do we consider SMP case?
> +     */
> +    if ( n->domain->arch.dirty.mode )
> +        restore_vlpt(n->domain);
> +

I though a bit more of this piece of code.

Your VLPT implementation uses xen_second which is shared between every
vCPU. Therefore restoring VLPT is pointless here.

In another hand, I didn't see anything which prevent you to migrate 2
domain at the same time. You will likely crash one of (if not both) the
guests.

Regards,

-- 
Julien Grall