Re: [Xen-devel] [PATCH v4 04/21] xen/arm: p2m: apply_p2m_changes: Only load domain P2M when we flush TLBs

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-04-22 at 14:14 +0100, Julien Grall wrote:
> apply_p2m_changes needs to switch to another VTTBR temporarily to avoid
> flush every TLBs.
> 
> As it's only needed there, we can restrict the scope where the VTTBR of this
> domain is loaded.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

Athough a flush_tlb_domain(d) type thing might be a nice addition.

> 
> ---
>     Changes in v4:
>         - Patch added
> ---
>  xen/arch/arm/p2m.c |   19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 0730da4..603c097 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -296,9 +296,6 @@ static int apply_p2m_changes(struct domain *d,
>  
>      spin_lock(&p2m->lock);
>  
> -    if ( d != current->domain )
> -        p2m_load_VTTBR(d);
> -
>      addr = start_gpaddr;
>      while ( addr < end_gpaddr )
>      {
> @@ -454,12 +451,17 @@ static int apply_p2m_changes(struct domain *d,
>  
>      if ( flush )
>      {
> -        /* At the beginning of the function, Xen is updating VTTBR
> -         * with the domain where the mappings are created. In this
> -         * case it's only necessary to flush TLBs on every CPUs with
> -         * the current VMID (our domain).
> +        /* Update the VTTBR if necessary with the domain where mappings
> +         * are created. In this case it's only necessary to flush TLBs
> +         * on every CPUs with the current VMID (our domain).
>           */
> +        if ( d != current->domain )
> +            p2m_load_VTTBR(d);
> +
>          flush_tlb();
> +
> +        if ( d != current->domain )
> +            p2m_load_VTTBR(current->domain);
>      }
>  
>      if ( op == ALLOCATE || op == INSERT )
> @@ -478,9 +480,6 @@ out:
>      if (second) unmap_domain_page(second);
>      if (first) unmap_domain_page(first);
>  
> -    if ( d != current->domain )
> -        p2m_load_VTTBR(current->domain);
> -
>      spin_unlock(&p2m->lock);
>  
>      return rc;



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel