>>> On 04.10.16 at 15:58, <andrew.coop...@citrix.com> wrote:
> On 04/10/16 14:39, Jan Beulich wrote:
>> @@ -770,9 +773,23 @@ static int _get_fpu(
>> unsigned long cr0;
>>
>> fail_if(!ops->read_cr);
>> + if ( type >= X86EMUL_FPU_xmm )
>> + {
>> + unsigned long cr4;
>> +
>> + rc = ops->read_cr(4, &cr4, ctxt);
>> + if ( rc != X86EMUL_OKAY )
>> + return rc;
>> + generate_exception_if(!(cr4 & ((type == X86EMUL_FPU_xmm)
>> + ? CR4_OSFXSR : CR4_OSXSAVE)),
>> + EXC_UD, -1);
>> + }
>> +
>> rc = ops->read_cr(0, &cr0, ctxt);
>> if ( rc != X86EMUL_OKAY )
>> return rc;
>> + if ( !(cr0 & CR0_PE) || (ctxt->regs->eflags & EFLG_VM) )
>> + generate_exception_if(type >= X86EMUL_FPU_ymm, EXC_UD, -1);
>
> Is this an appropriate check to do here? This restriction is because
> the VEX prefix isn't permitted in real/vm86 mode.
>
> Instead of a generate_exception_if(), I would instead have an ASSERT()
> that we don't actually reach this point.
Hmm, that's right.
Jan
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