Re: struct mctelem_cookie missing definition

[Jan Beulich <jbeulich@xxxxxxxx>]

On 13.02.2025 02:34, Andrew Cooper wrote:
> On 13/02/2025 1:25 am, Stefano Stabellini wrote:
>> Hi all,
>>
>> I am looking through the few remaining MISRA violations that we have
>> left.  One of them is R11.2:
>>
>> https://saas.eclairit.com:3787/fs/var/local/eclair/xen-project.ecdf/xen-project/hardware/xen/ECLAIR_normal/staging/X86_64/9118578464/PROJECT.ecd;/by_service/MC3A2.R11.2.html#{%22select%22:true,%22selection%22:{%22hiddenAreaKinds%22:[],%22hiddenSubareaKinds%22:[],%22show%22:false,%22selector%22:{%22enabled%22:true,%22negated%22:true,%22kind%22:0,%22domain%22:%22kind%22,%22inputs%22:[{%22enabled%22:true,%22text%22:%22violation%22}]}}}
>>
>> Specifically, mctelem_cookie_t is a pointer to incomplete type and
>> therefore COOKIE2MCTE triggers a "conversion between a pointer to an
>> incomplete type and any other type".
>>
>> mctelem_cookie_t is defined as:
>>
>> typedef struct mctelem_cookie *mctelem_cookie_t;
>>
>> I am looking through the code and I genuinely cannot find the definition
>> of struct mctelem_cookie.
>>
>> If mctelem_cookie_t is only used as a pointer, wouldn't it make more
>> sense to do:
>>
>> typedef struct mctelem_ent *mctelem_cookie_t;
>>
>> ?
>>
>> What am I missing?
> 
> Nothing.  Or perhaps the twisted thinking of the original author.
> 
> It is genuinely a pointer type (== known size) which you can't deference
> (because there is no definition), and can only operate on by casting to
> an integer.  Except the code also requires it to be a uint64_t which is
> why there's some fun disabling of relevant hypercalls for compat guests.

That "fun disabling" is for the COMPAT=n case afaics, not for compat guests.
Or else I screwed up in d23d792478db.

Jan