Re: [PATCH] x86/AMD: fold redundant parameters of cpu_has_amd_erratum()

[Boris Ostrovsky <boris.ostrovsky@amd.com>]

On 12/16/11 10:23, Jan Beulich wrote:
> The boolean 'osvw' indicator and 'osvw_id' can be folded - the function
> can as well distinguish the non-OSVW case by checking for a negative
> 'osvw_id'. That way the whole variable argument list processing is only
> needed on the legacy code path.
>
> Signed-off-by: Jan Beulich<jbeulich@suse.com>

Acked-by: Boris Ostrovsky <boris.ostrovsky@amd.com>

>
> --- a/xen/arch/x86/cpu/amd.c
> +++ b/xen/arch/x86/cpu/amd.c
> @@ -186,7 +186,7 @@ static void __devinit set_cpuidmask(cons
>    * Check for the presence of an AMD erratum. Arguments are defined in amd.h
>    * for each known erratum. Return 1 if erratum is found.
>    */
> -int cpu_has_amd_erratum(const struct cpuinfo_x86 *cpu, int osvw, ...)
> +int cpu_has_amd_erratum(const struct cpuinfo_x86 *cpu, int osvw_id, ...)
>   {
>   	va_list ap;
>   	u32 range;
> @@ -195,27 +195,24 @@ int cpu_has_amd_erratum(const struct cpu
>   	if (cpu->x86_vendor != X86_VENDOR_AMD)
>   		return 0;
>
> -	va_start(ap, osvw);
> +	if (osvw_id>= 0&&  cpu_has(cpu, X86_FEATURE_OSVW)) {
> +		u64 osvw_len;
>
> -	if (osvw) {
> -		u16 osvw_id = va_arg(ap, int);
> +		rdmsrl(MSR_AMD_OSVW_ID_LENGTH, osvw_len);
>
> -		if (cpu_has(cpu, X86_FEATURE_OSVW)) {
> -			u64 osvw_len;
> -			rdmsrl(MSR_AMD_OSVW_ID_LENGTH, osvw_len);
> -
> -			if (osvw_id<  osvw_len) {
> -				u64 osvw_bits;
> -				rdmsrl(MSR_AMD_OSVW_STATUS + (osvw_id>>  6),
> -				       osvw_bits);
> +		if (osvw_id<  osvw_len) {
> +			u64 osvw_bits;
>
> -				va_end(ap);
> -				return (osvw_bits>>  (osvw_id&  0x3f))&  0x01;
> -			}
> +			rdmsrl(MSR_AMD_OSVW_STATUS + (osvw_id>>  6),
> +			       osvw_bits);
> +
> +			return (osvw_bits>>  (osvw_id&  0x3f))&  1;
>   		}
>   	}
>
>   	/* OSVW unavailable or ID unknown, match family-model-stepping range */
> +	va_start(ap, osvw_id);
> +
>   	ms = (cpu->x86_model<<  4) | cpu->x86_mask;
>   	while ((range = va_arg(ap, int))) {
>   		if ((cpu->x86 == AMD_MODEL_RANGE_FAMILY(range))&&
> --- a/xen/include/asm-x86/amd.h
> +++ b/xen/include/asm-x86/amd.h
> @@ -119,8 +119,8 @@
>    *
>    */
>
> -#define AMD_LEGACY_ERRATUM(...)         0 /* legacy */, __VA_ARGS__, 0
> -#define AMD_OSVW_ERRATUM(osvw_id, ...)  1 /* osvw */, osvw_id, __VA_ARGS__, 0
> +#define AMD_LEGACY_ERRATUM(...)         -1 /* legacy */, __VA_ARGS__, 0
> +#define AMD_OSVW_ERRATUM(osvw_id, ...)  osvw_id, __VA_ARGS__, 0
>   #define AMD_MODEL_RANGE(f, m_start, s_start, m_end, s_end)              \
>       ((f<<  24) | (m_start<<  16) | (s_start<<  12) | (m_end<<  4) | (s_end))
>   #define AMD_MODEL_RANGE_FAMILY(range)   (((range)>>  24)&  0xff)
>
>
>