Re: [Xen-devel] [PATCH] x86/mm: Drop {HAP,SHADOW}_ERROR() wrappers

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.08.18 at 17:20, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 30/08/18 16:15, Jan Beulich wrote:
>>>>> On 28.08.18 at 20:11, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> @@ -2478,9 +2478,7 @@ sh_map_and_validate_gl4e(struct vcpu *v, mfn_t gl4mfn,
>>>                                  shadow_l4_index,
>>>                                  validate_gl4e);
>>>  #else // ! GUEST_PAGING_LEVELS >= 4
>>> -    SHADOW_ERROR("called in wrong paging mode!\n");
>>> -    BUG();
>>> -    return 0;
>>> +    BUG(); /* Called in wrong paging mode! */
>>>  #endif
>>>  }
>> Isn't this going to break the build for certain older gcc versions?
>> ISTR some similar problems in the past.
> 
> Perhaps, but since this code was written, BUG() has gained an
> unreachable() hint.  As other examples of this code like this compile, I
> don't think this is going to be a problem.

The problem(s) I think I recall certainly post-date the introduction of
unreachable(). Perhaps whether a compiler would produce a
diagnostic depends on other factors as well. I'm not objecting to this
going in unchanged; in the worst case we'll have to re-introduce the
"return" later on.

Jan



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