Re: [Xen-devel] [PATCH 6/8] x86/emul: Support speculative MSR reads

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.12.16 at 11:09, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -1319,7 +1319,7 @@ in_longmode(
>      uint64_t efer;
>  
>      if ( !ops->read_msr ||
> -         unlikely(ops->read_msr(MSR_EFER, &efer, ctxt) != X86EMUL_OKAY) )
> +         unlikely(ops->read_msr(MSR_EFER, &efer, false, ctxt) != 
> X86EMUL_OKAY) )

Don't you mean "true" here (and the "no functional change" dropped
from the commit message)?

> @@ -4412,7 +4412,7 @@ x86_emulate(
>          {
>              uint64_t tsc_aux;
>              fail_if(ops->read_msr == NULL);
> -            if ( (rc = ops->read_msr(MSR_TSC_AUX, &tsc_aux, ctxt)) != 0 )
> +            if ( (rc = ops->read_msr(MSR_TSC_AUX, &tsc_aux, false, ctxt)) != 
> 0 )

And here too? And basically everywhere except in the actual
RDMSR emulation code? Which then raises the question
whether this extra parameter is a useful thing to have, as
there's exactly one place where you want the #GP(0). I
guess the hook should simply return boolean, and the caller
determine whether to generate an exception.

Jan


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