Re: [PATCH for-4.16] x86/passthrough: Fix hvm_gsi_eoi() build with GCC 12

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.11.2021 09:33, Roger Pau Monné wrote:
> On Thu, Nov 04, 2021 at 01:17:53PM +0100, Jan Beulich wrote:
>> On 04.11.2021 11:48, Andrew Cooper wrote:
>>> If your answer is "well actually, we didn't mean to say 'if a GSI is
>>> mapped' in the comment, and here's a different predicate which actually
>>> inspects the state of a dpci object for validity", then fine -  that
>>> will shut the compiler up because you're no longer checking for the
>>> NULLness of a pointer to a sub-object of a non-NULL pointer, but that's
>>> a bugfix which needs backporting several releases too.
>>>
>>> The current logic is not correct, and does not become correct by trying
>>> pass blame to the compiler.
>>
>> I have yet to understand in which way you deem the current logic to not
>> be correct. I'm sorry for being dense.
>>
>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102967 is the GCC bug, but
>>> the result of it was them persuading me that the diagnostic was
>>> legitimate, even if currently expressed badly.  They've agreed to fix
>>> how it is expressed, but I doubt you'll persuade them that the trigger
>>> for the diagnostic in the first place was wrong.
>>
>> Well, thanks for the pointer in any event. I've commented there as well.
> 
> Did we get any resolution out of this?

I don't think we did. I'm still struggling to understand Andrew's way
of thinking.

> It would be good IMO if we could build out of the box with GCC 12
> instead of having to backport fixes later on.

I guess gcc12 is too far from getting released that there could be any
guarantee for no further issues to get exposed by that point. It has
also been common for us to backport fixes and workarounds when new
compiler versions appear.

I could agree to being proactive if the change to make to our code was
uncontroversial.

Jan