Re: [Xen-devel] [PATCH v8 19/50] x86emul: support AVX512F floating-point conversion insns

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.05.19 at 13:33, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 15/03/2019 10:47, Jan Beulich wrote:
>> @@ -9312,7 +9386,8 @@ x86_emulate(
>>  
>>          if ( ea.type == OP_MEM )
>>          {
>> -            rc = ops->write(ea.mem.seg, ea.mem.off, mmvalp, 8 << vex.l, 
>> ctxt);
>> +            rc = ops->write(ea.mem.seg, truncate_ea(ea.mem.off + 
>> first_byte),
>> +                            (void *)mmvalp + first_byte, op_bytes, ctxt);
>>              if ( rc != X86EMUL_OKAY )
>>              {
>>                  asm volatile ( "ldmxcsr %0" :: "m" (mxcsr) );
> 
> This hunk doesn't appear to fit with the rest of the patch, because it
> isn't the first use of first_byte.
> 
> Have we been subtly broken before?

I don't think so, no, but I admit I'm not sure I understand what
you're saying above. The use of first_byte here is of course not
the first use - it gets set in the hunk further up. The AVX form of
VCVTPS2PH does not support fault suppression (as that's an
AVX512 feature), and hence no such adjustment was needed
here before.

Jan



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