Re: [Xen-devel] [PATCH v4 3/5] xen/arm: clean and invalidate all guest caches by VMID after domain build.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.02.14 at 13:12, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> --- a/xen/arch/arm/domctl.c
> +++ b/xen/arch/arm/domctl.c
> @@ -17,6 +17,20 @@ long arch_do_domctl(struct xen_domctl *domctl, struct 
> domain *d,
>  {
>      switch ( domctl->cmd )
>      {
> +    case XEN_DOMCTL_cacheflush:
> +    {
> +        unsigned long s = domctl->u.cacheflush.start_pfn;
> +        unsigned long e = s + domctl->u.cacheflush.nr_pfns;
> +
> +        if ( e < s )
> +            return -EINVAL;
> +
> +        if ( get_order_from_pages(domctl->u.cacheflush.nr_pfns) > MAX_ORDER )
> +            return -EINVAL;

get_order_from_pages() takes an unsigned long, while xen_pfn_t
is - iirc - 64-bits even on arm32. So you're not checking the full
passed in value, yet use the full one in the calculation of "e" (which
is what gets passed down).

Also, did you consider the nr_pfns == 0 case? At present, due to
the way get_order_from_pages() works, this will produce -EINVAL.
I'm not sure that's intended.

> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -885,6 +885,17 @@ struct xen_domctl_set_max_evtchn {
>  typedef struct xen_domctl_set_max_evtchn xen_domctl_set_max_evtchn_t;
>  DEFINE_XEN_GUEST_HANDLE(xen_domctl_set_max_evtchn_t);
>  
> +/*
> + * ARM: Clean and invalidate caches associated with given region of
> + * guest memory.
> + */
> +struct xen_domctl_cacheflush {
> +    /* IN: page range to flush. */
> +    xen_pfn_t start_pfn, nr_pfns;
> +};

The name here (and of the libxc interface) is now certainly
counterintuitive. But it's a domctl (and an internal interface),
which we can change post-4.4 (I'd envision it to actually take
a flags parameter indicating the kind of flush that's wanted).

> --- a/xen/xsm/flask/hooks.c
> +++ b/xen/xsm/flask/hooks.c
> @@ -737,6 +737,9 @@ static int flask_domctl(struct domain *d, int cmd)
>      case XEN_DOMCTL_set_max_evtchn:
>          return current_has_perm(d, SECCLASS_DOMAIN2, 
> DOMAIN2__SET_MAX_EVTCHN);
>  
> +    case XEN_DOMCTL_cacheflush:
> +         return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__CACHEFLUSH);

Hard tab.

Jan


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