Re: [PATCH] xen/arm: Implement domain_get_maximum_gpfn

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

Hello Tamas,

On 03/09/14 02:00, Tamas K Lengyel wrote:
>
>
>
> On Wed, Sep 3, 2014 at 10:44 AM, Ian Campbell <Ian.Campbell@citrix.com
> <mailto:Ian.Campbell@citrix.com>> wrote:
>
>     On Mon, 2014-09-01 at 17:32 -0400, Julien Grall wrote:
>      > Hi Ian,
>      >
>      > On 16/07/14 12:02, Ian Campbell wrote:
>      > > I'd much prefer to just have the fix to xc_dom_gnttab_hvm_seed
>     for ARM
>      > > and continue to punt on this interface until it is actually
>     needed by
>      > > something unavoidable on the guest side (and simultaneously
>     hope that
>      > > day never comes...).
>      >
>      > This patch is a requirement to make Xen Memory access working on ARM.
>      > Could you reconsider the possibility to apply this patch on Xen?
>
>     Needs more rationale as to why it is required for Xen Memory (do you
>     mean xenaccess?). I assume I'll find that in the relevant thread once I
>     get to it?
>
>
> It's used in a non-critical sanity check for performance reasons, as
> seen here:
> https://github.com/tklengyel/xen/blob/arm_memaccess3/xen/common/mem_access.c#L75.
> Without the sanity check we might attempt to set mem_access permissions
> on gpfn's that don't exist for the guest. It wouldn't break anything to
> do that but if we know beforehand that the gpfn is outside the scope of
> what the guest has we can skip the entire thing.

It might be better if you carry this patch on your series.

Regards,

-- 
Julien Grall