Re: [PATCH V5 00/22] IOREQ feature (+ virtio-mmio) on Arm

[Oleksandr <olekstysh@gmail.com>]

On 26.01.21 01:20, Julien Grall wrote:

Hi Julien, Stefano

> On Mon, 25 Jan 2021 at 20:56, Stefano Stabellini <sstabellini@kernel.org> wrote:
>> Julien,
> Hi,
>
>> This seems to be an arm randconfig failure:
>>
>> https://gitlab.com/xen-project/patchew/xen/-/pipelines/246632953
>> https://gitlab.com/xen-project/patchew/xen/-/jobs/985455044
> Thanks! The error is:
>
> #'target_mem_ref' not supported by expression#'memory.c: In function
> 'do_memory_op':
> memory.c:1210:18: error:  may be used uninitialized in this function
> [-Werror=maybe-uninitialized]
>   1210 |             rc = set_foreign_p2m_entry(currd, d, gfn_list[i],
>        |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   1211 |                                        _mfn(mfn_list[i]));
>        |                                        ~~~~~~~~~~~~~~~~~~
>
> I found a few references online of the error message, but it is not
> clear what it means. From a quick look at Oleksandr's branch, I also
> can't spot anything unitialized. Any ideas?
It seems that error happens if *both* CONFIG_GRANT_TABLE and 
CONFIG_IOREQ_SERVER are disabled. Looks like that mfn_list is 
initialized either in acquire_grant_table() or in acquire_ioreq_server().
If these options disabled then corresponding helpers are just stubs, so 
indeed that mfn_list gets uninitialized. But, I am not sure why gcc 
complains about it as set_foreign_p2m_entry() is *not* going to be 
called in that case???



-- 
Regards,

Oleksandr Tyshchenko