Re: [Xen-devel] [PATCH v5 2/2] xen: move TLB-flush filtering out into populate_physmap during vm creation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.09.16 at 04:50, <dongli.zhang@xxxxxxxxxx> wrote:
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -1004,6 +1004,14 @@ int domain_unpause_by_systemcontroller(struct domain 
> *d)
>  {
>      int old, new, prev = d->controller_pause_count;
>  
> +    /*
> +     * We record this information here for populate_physmap to figure out
> +     * that the domain has finished being created. In fact, we're only
> +     * allowed to set the MEMF_no_tlbflush flag during VM creation.
> +     */
> +    if ( unlikely(!d->creation_finished) )
> +        d->creation_finished = true;

Already on a much earlier version it was pointed out that the
conditional here is rather pointless and potentially confusing.
Please remove it unless you have a very good reason for it to
be there.

> @@ -150,6 +152,17 @@ static void populate_physmap(struct memop_args *a)
>                              max_order(curr_d)) )
>          return;
>  
> +    /*
> +     * With MEMF_no_tlbflush set, alloc_heap_pages() will ignore
> +     * TLB-flushes. After VM creation, this is a security issue (it can
> +     * make pages accessible to guest B, when guest A may still have a
> +     * cached mapping to them). So we only do this only during domain

Duplicate "only".

> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -474,6 +474,12 @@ struct domain
>          unsigned int guest_request_enabled       : 1;
>          unsigned int guest_request_sync          : 1;
>      } monitor;
> +
> +    /*
> +     * Set to true at the very end of domain creation, when the domain is
> +     * unpaused for the first time by the systemcontroller.
> +     */
> +    bool creation_finished;

Please place this next to the other group of booleans, the more that
there is a 1 byte padding slot available there (or even 2 bytes when
!CONFIG_HAS_PASSTHROUGH).

Jan


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