Re: [Xen-devel] [Patch v4] x86/traps: improvements to {rd, wr}msr_hypervisor_regs()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.10.13 at 15:46, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -595,55 +595,50 @@ DO_ERROR_NOCODE(TRAP_copro_error,     coprocessor_error)
>  DO_ERROR(       TRAP_alignment_check, alignment_check)
>  DO_ERROR_NOCODE(TRAP_simd_error,      simd_coprocessor_error)
>  
> +/*
> + * Returns 0 if not handled, and non-0 for error. (The calling semantics are
> + * in need of some work)
> + */
>  int rdmsr_hypervisor_regs(uint32_t idx, uint64_t *val)
>  {

The comment here still isn't in line with the existing callers. Non-
zero means success afaict. There simply is no path resulting in
an error here so far.

> +    switch ( idx - base )
>      {
> -    case 0:
> +    case 0: /* Write hypercall page.  Reads are invalid. Hand a #GP back. */
>      {
>          *val = 0;
> -        break;
> +        return 1;

And the above means that there's no #GP being "handed back"
here either.

Jan


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