Subject: Re: [Xen-devel] [PATCH v4] xen/grant-table: Avoid m2p_override during mapping

From: David Vrabel <[email-masked]>
Date: Wed, 22 Jan 2014 10:58:00 +0000

On 21/01/14 20:22, Zoltan Kiss wrote:
> The grant mapping API does m2p_override unnecessarily: only gntdev needs it,
> for blkback and future netback patches it just cause a lock contention, as
> those pages never go to userspace. Therefore this series does the following:
> - the original functions were renamed to __gnttab_[un]map_refs, with a new
>   parameter m2p_override
> - based on m2p_override either they follow the original behaviour, or just set
>   the private flag and call set_phys_to_machine
> - gnttab_[un]map_refs are now a wrapper to call __gnttab_[un]map_refs with
>   m2p_override false
> - a new function gnttab_[un]map_refs_userspace provides the old behaviour
> 
> v2:
> - move the storing of the old mfn in page->index to gnttab_map_refs
> - move the function header update to a separate patch
> 
> v3:
> - a new approach to retain old behaviour where it needed
> - squash the patches into one
> 
> v4:
> - move out the common bits from m2p* functions, and pass pfn/mfn as parameter
> - clear page->private before doing anything with the page, so m2p_find_override
>   won't race with this

I would prune this version information out of the commit message.

> Signed-off-by: Zoltan Kiss <[email-masked]>
> Suggested-by: David Vrabel <[email-masked]>

Reviewed-by: David Vrabel <[email-masked]>

But I think this needs Stefano's ack.

It would be useful to get this into 3.14 if possible.

David