Re: [Xen-devel] [PATCH RESEND 2/4] qdisk, hw/block/xen_disk: Removal of grant mapping

[Paulina Szubarczyk <paulinaszubarczyk@xxxxxxxxx>]

On Thu, 2016-06-02 at 11:41 +0200, Roger Pau Monné wrote:
> On Tue, May 31, 2016 at 06:44:56AM +0200, Paulina Szubarczyk wrote:
> > Grant mapping related functions and variables are removed
> > on behalf of grant copy operation introduced in following commits.
> 
> As David says, you should not remove this before adding a suitable 
> replacement, or else you are breaking the build.
> 
> Also, the grant map and unmap mode should be keep (we can talk about 
> removing persistent grants support), because there are gnttab devices out 
> there that only support grant map/unmap, but not grant copy IIRC.
> 
Ok, so there should be a conditional path in this case, but is there a
way to check if grant copy is supported? 
If not it might maybe be checked in run-time for example trying to issue
grant copy and if it fails for the first time set that it is not
supported and proceed with grant map?

Paulina



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