Re: [PATCH v2 09/11] xen/memory: Fix mapping grant tables with XENMEM_acquire_resource

[Andrew Cooper <amc96@xxxxxxxxx>]

On 11/01/2021 20:05, Andrew Cooper wrote:
>>> --- a/xen/common/memory.c
>>> +++ b/xen/common/memory.c
>>> @@ -1027,17 +1027,31 @@ static unsigned int resource_max_frames(struct 
>>> domain *d,
>>>      }
>>>  }
>>>  
>>> +/*
>>> + * Returns -errno on error, or positive in the range [1, nr_frames] on
>>> + * success.  Returning less than nr_frames contitutes a request for a
>>> + * continuation.
>>> + */
>>> +static int _acquire_resource(
>>> +    struct domain *d, unsigned int type, unsigned int id, unsigned long 
>>> frame,
>>> +    unsigned int nr_frames, xen_pfn_t mfn_list[])
>> As per the comment the return type may again want to be "long" here.
>> Albeit I realize the restriction to (UINT_MAX >> MEMOP_EXTENT_SHIFT)
>> makes this (and the other place above) only a latent issue for now,
>> so it may well be fine to be left as is.
> Hmm yes - it should be long, because per the ABI we still should be able
> to return 0xffffffff to a caller in the success case.
>
> I'll update.

Actually, no.  Wrong half the hypercall.

For _acquire_resource(), the return value is bound by nr_frames which is
a maximum of 32, and is unlikely to grow substantially from this.

~Andrew