Re: [Xen-devel] [PATCH for-4.10 5/5] tools/dombuilder: Prevent failures of xc_dom_gnttab_init()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 06/10/17 18:39, Wei Liu wrote:
> On Thu, Oct 05, 2017 at 07:23:44PM +0100, Andrew Cooper wrote:
>> Recent changes in grant table configuration have caused calls to
>> xc_dom_gnttab_init() to fail if not proceeded with a call to
>> xc_domain_set_gnttab_limits().  This is backwards from the point of view of
>> 3rd party dombuilder users.
>>
>> Add max_{grant,maptrack}_frames parameters to struct xc_dom_image, and 
>> require
>> them to be set by callers using xc_dom_gnttab_init().  Libxl, which uses
>> xc_dom_gnttab_init() itself is updated appropriately.
>>
> Either the code as-is or this patch requires modification to dombuilder
> users, so I'm not too convinced if the original code is backwards.

For dombuilder users who currently call xc_dom_gnttab_init(), it is
antisocial for them to suddenly find they need to call
xc_domain_set_gnttab_limits() before xc_dom_gnttab_init() will succeed,
and _init() can reasonably be expected to DTRT.

Whatever happens, before or after this series, all dombuilder users need
to modify their calls.

I argue that with this series in place, the caller has a far more
rational interface to use, which is consistent across guests types.

>
> I'm not too fussed about how things are done as long as they continue to
> work, so with Roger's comments addressed:
>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

Thanks,

~Andrew

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