[MODERATED] Re: [PATCH 1/3] V5 more sampling fun 1

[Kees Cook <keescook@chromium.org>]

On Mon, Mar 16, 2020 at 05:56:27PM -0700, speck for mark gross wrote:
> From: mark gross <mgross@linux.intel.com>
> Subject: [PATCH 1/3] x86/cpu: Add stepping field to x86_cpu_id structure
> 
> Intel uses the same family/model for several CPUs. Sometimes the
> stepping must be checked to tell them apart.
> 
> On X86 there can be at most 16 steppings, add steppings bitmask to
> x86_cpu_id and X86_MATCH_VENDOR_FAMILY_MODEL_STEPPING_FEATURE macro and
> support for matching against family/model/stepping.
> 
> Signed-off-by: Mark Gross <mgross@linux.intel.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> Reviewed-by: Tony Luck <tony.luck@intel.com>
> ---
>  arch/x86/include/asm/cpu_device_id.h | 26 +++++++++++++++++++++++---
>  arch/x86/kernel/cpu/match.c          |  7 ++++++-
>  include/linux/mod_devicetable.h      |  2 ++
>  3 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/include/asm/cpu_device_id.h b/arch/x86/include/asm/cpu_device_id.h
> index cf3d621c6892..d8ecd0d72e04 100644
> --- a/arch/x86/include/asm/cpu_device_id.h
> +++ b/arch/x86/include/asm/cpu_device_id.h
> @@ -21,11 +21,12 @@
>  #define X86_CENTAUR_FAM6_NANO		0xf
>  
>  /**
> - * X86_MATCH_VENDOR_FAM_MODEL_FEATURE - Base macro for CPU matching
> + * X86_MATCH_VENDOR_FAM_MODEL_STEPPING_FEATURE - Base macro for CPU matching
>   * @_vendor:	The vendor name, e.g. INTEL, AMD, HYGON, ..., ANY
>   *		The name is expanded to X86_VENDOR_@_vendor
>   * @_family:	The family number or X86_FAMILY_ANY
>   * @_model:	The model number, model constant or X86_MODEL_ANY
> + * @_steppings:	Bitmask for steppings, stepping constant or X86_STEPPING_ANY
>   * @_feature:	A X86_FEATURE bit or X86_FEATURE_ANY
>   * @_data:	Driver specific data or NULL. The internal storage
>   *		format is unsigned long. The supplied value, pointer
> @@ -37,15 +38,34 @@
>   * into another macro at the usage site for good reasons, then please
>   * start this local macro with X86_MATCH to allow easy grepping.
>   */
> -#define X86_MATCH_VENDOR_FAM_MODEL_FEATURE(_vendor, _family, _model,	\
> -					   _feature, _data) {		\
> +#define X86_MATCH_VENDOR_FAM_MODEL_STEPPING_FEATURE(_vendor, _family, _model, \
> +						    _steppings, _feature, _data) { \
>  	.vendor		= X86_VENDOR_##_vendor,				\
>  	.family		= _family,					\
>  	.model		= _model,					\
> +	.steppings	= _steppings,					\
>  	.feature	= _feature,					\
>  	.driver_data	= (unsigned long) _data				\
>  }
>  
> +/**
> + * X86_MATCH_VENDOR_FAM_MODEL_FEATURE - Base macro for CPU matching
> + * @_vendor:	The vendor name, e.g. INTEL, AMD, HYGON, ..., ANY
> + *		The name is expanded to X86_VENDOR_@_vendor
> + * @_family:	The family number or X86_FAMILY_ANY
> + * @_model:	The model number, model constant or X86_MODEL_ANY
> + * @_feature:	A X86_FEATURE bit or X86_FEATURE_ANY
> + * @_data:	Driver specific data or NULL. The internal storage
> + *		format is unsigned long. The supplied value, pointer
> + *		etc. is casted to unsigned long internally.
> + *
> + * The steppings arguments of X86_MATCH_VENDOR_FAM_MODEL_STEPPING_FEATURE() is
> + * set to wildcards.
> + */
> +#define X86_MATCH_VENDOR_FAM_MODEL_FEATURE(vendor, family, model, feature, data) \
> +	X86_MATCH_VENDOR_FAM_MODEL_STEPPING_FEATURE(vendor, family, model, \
> +						X86_STEPPING_ANY, feature, data)
> +
>  /**
>   * X86_MATCH_VENDOR_FAM_FEATURE - Macro for matching vendor, family and CPU feature
>   * @vendor:	The vendor name, e.g. INTEL, AMD, HYGON, ..., ANY
> diff --git a/arch/x86/kernel/cpu/match.c b/arch/x86/kernel/cpu/match.c
> index d3482eb43ff3..dac48301b5a7 100644
> --- a/arch/x86/kernel/cpu/match.c
> +++ b/arch/x86/kernel/cpu/match.c
> @@ -39,13 +39,18 @@ const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match)
>  	const struct x86_cpu_id *m;
>  	struct cpuinfo_x86 *c = &boot_cpu_data;
>  
> -	for (m = match; m->vendor | m->family | m->model | m->feature; m++) {
> +	for (m = match;
> +	     m->vendor | m->family | m->model | m->steppings | m->feature;
> +	     m++) {
>  		if (m->vendor != X86_VENDOR_ANY && c->x86_vendor != m->vendor)
>  			continue;
>  		if (m->family != X86_FAMILY_ANY && c->x86 != m->family)
>  			continue;
>  		if (m->model != X86_MODEL_ANY && c->x86_model != m->model)
>  			continue;
> +		if (m->steppings != X86_STEPPING_ANY &&
> +				!(BIT(c->x86_stepping) & m->steppings))
> +			continue;
>  		if (m->feature != X86_FEATURE_ANY && !cpu_has(c, m->feature))
>  			continue;
>  		return m;
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index 4c2ddd0941a7..0754b8d71262 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -663,6 +663,7 @@ struct x86_cpu_id {
>  	__u16 vendor;
>  	__u16 family;
>  	__u16 model;
> +	__u16 steppings;
>  	__u16 feature;	/* bit index */
>  	kernel_ulong_t driver_data;
>  };
> @@ -671,6 +672,7 @@ struct x86_cpu_id {
>  #define X86_VENDOR_ANY 0xffff
>  #define X86_FAMILY_ANY 0
>  #define X86_MODEL_ANY  0
> +#define X86_STEPPING_ANY 0
>  #define X86_FEATURE_ANY 0	/* Same as FPU, you can't test for that */
>  
>  /*
> -- 
> 2.17.1

-- 
Kees Cook