Re: [Xen-devel] [PATCH 5/5] tools/libxenctrl: use new xenforeignmemory API to seed grant table

[Juergen Gross <jgross@xxxxxxxx>]

On 04/08/17 15:21, Wei Liu wrote:
> On Fri, Aug 04, 2017 at 03:02:03PM +0200, Marek Marczykowski-Górecki wrote:
>> On Fri, Aug 04, 2017 at 01:26:21PM +0100, Wei Liu wrote:
>>> On Wed, Aug 02, 2017 at 10:59:49AM +0100, Paul Durrant wrote:
>>>> A previous patch added support for priv-mapping guest resources directly
>>>> (rather than having to foreign-map, which requires P2M modification for
>>>> HVM guests).
>>>>
>>>> This patch makes use of the new API to seed the guest grant table unless
>>>> the underlying infrastructure (i.e. privcmd) doesn't support it, in which
>>>> case the old scheme is used.
>>>>
>>>
>>> The code mostly looks fine.
>>>
>>> What's the benefit of doing this?
>>
>> Also, I see changed signature of xc_dom_gnttab_seed (it got is_hvm
>> parameter). Wei, what is the policy for backward incompatible libxc API
>> changes?
> 
> libxc isn't stable, so functions might get deleted / updated at any
> point.
> 
> Most libxc functions are quite simple and are quite "close" to the
> hypervisor.
> 
> The non-trivial functions I know of are VMI related ones but I think
> users in that area already have the right expectation.
> 
> An important user of unstable libxc APIs is QEMU. It probes for specific
> functions in the configure script to handle compatibility issues.

Right now qemu can just use the version of libxc instead of doing it via
tests. :-)


Juergen

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