Re: [Xen-devel] [PATCH] x86/grant: Use explicit instruction size in gnttab_clear_flags()

[Jan Beulich <JBeulich@xxxxxxxx>]

On 09.07.2019 00:15, Andrew Cooper wrote:
> The OpenSUSE Leap compilers complain about ambiguity:
> 
> In file included from grant_table.c:33:
> In file included from ...xen/include/xen/grant_table.h:30:
> ...xen/include/asm/grant_table.h:67:19: error: ambiguous instructions require
> an explicit suffix (could be 'andb', 'andw', 'andl', or 'andq')
>      asm volatile ("lock and %1,%0" : "+m" (*addr) : "ir" ((uint16_t)~mask));
>                    ^
> <inline asm>:1:2: note: instantiated into assembly here
>          lock and $-17,(%rsi)
>          ^

Wow - pretty helpful improvement to the compiler, albeit I have
no idea how this actually work. The assembler would have picked
andl here.

> Full logs: https://gitlab.com/xen-project/people/andyhhp/xen/-/jobs/247600284
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
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