Re: [PATCH 03/10] tools/libxg: Fix uninitialised variable in meminit()

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 12/02/2021 15:55, Julien Grall wrote:
> Hi Andrew,
>
> On 12/02/2021 15:39, Andrew Cooper wrote:
>> Various version of gcc, when compiling with -Og, complain:
>>
>>    xg_dom_arm.c: In function 'meminit':
>>    xg_dom_arm.c:420:19: error: 'p2m_size' may be used uninitialized
>> in this function [-Werror=maybe-uninitialized]
>>      420 |     dom->p2m_size = p2m_size;
>>          |     ~~~~~~~~~~~~~~^~~~~~~~~~
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>
> This was reported nearly 3 years ago (see [1]) and it is pretty sad
> this was never merged :(.

:( We've got far too many patches which fall through the cracks like this.

>
>> ---
>> CC: Ian Jackson <iwj@xenproject.org>
>> CC: Wei Liu <wl@xen.org>
>> CC: Stefano Stabellini <sstabellini@kernel.org>
>> CC: Julien Grall <julien@xen.org>
>>
>> Julien/Stefano: I can't work out how this variable is supposed to
>> work, and
>> the fact that it isn't a straight accumulation across the RAM banks
>> looks
>> suspect.
>
> It looks buggy, but the P2M is never used on Arm. In fact, you sent a
> patch a year ago to drop it (see [2]). It would be nice to revive it.


That series was committed more than a year ago - ee21f10d70^..97e34ad22d
- and tbh, I'd forgotten about it.

In light of that, I think I'll just delete the p2m_size references
here.  It's easy to prove correctness via inspection, and removes a
dubious construct entirely.

~Andrew