Re: [PATCH 1/7] x86/intel_rdt: Intel Cache Allocation Technology detection

[Borislav Petkov <bp@alien8.de>]

On Tue, Feb 24, 2015 at 03:16:38PM -0800, Vikas Shivappa wrote:
> This patch adds support for the new Cache Allocation Technology (CAT)
> feature found in future Intel Xeon processors. CAT is part of Intel
> Resource Director Technology(RDT) which enables sharing of processor
> resources. This patch includes CPUID enumeration routines for CAT and
> new values to track CAT resources to the cpuinfo_x86 structure.
> 
> Cache Allocation Technology(CAT) provides a way for the Software
> (OS/VMM) to restrict cache allocation to a defined 'subset' of cache
> which may be overlapping with other 'subsets'.  This feature is used
> when allocating a line in cache ie when pulling new data into the cache.
> The programming of the h/w is done via programming  MSRs.
> 
> More information about CAT be found in the Intel (R) x86 Architecture
> Software Developer Manual, section 17.15.
> 
> Signed-off-by: Vikas Shivappa <vikas.shivappa@linux.intel.com>
> ---
>  arch/x86/include/asm/cpufeature.h |  6 ++++-
>  arch/x86/include/asm/processor.h  |  3 +++
>  arch/x86/kernel/cpu/Makefile      |  1 +
>  arch/x86/kernel/cpu/common.c      | 15 ++++++++++++
>  arch/x86/kernel/cpu/intel_rdt.c   | 51 +++++++++++++++++++++++++++++++++++++++
>  init/Kconfig                      | 11 +++++++++
>  6 files changed, 86 insertions(+), 1 deletion(-)
>  create mode 100644 arch/x86/kernel/cpu/intel_rdt.c
> 
> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> index 54fd8eb..d97b785 100644
> --- a/arch/x86/include/asm/cpufeature.h
> +++ b/arch/x86/include/asm/cpufeature.h
> @@ -12,7 +12,7 @@
>  #include <asm/disabled-features.h>
>  #endif
>  
> -#define NCAPINTS	13	/* N 32-bit words worth of info */
> +#define NCAPINTS	14	/* N 32-bit words worth of info */
>  #define NBUGINTS	1	/* N 32-bit bug flags */
>  
>  /*
> @@ -227,6 +227,7 @@
>  #define X86_FEATURE_RTM		( 9*32+11) /* Restricted Transactional Memory */
>  #define X86_FEATURE_CQM		( 9*32+12) /* Cache QoS Monitoring */
>  #define X86_FEATURE_MPX		( 9*32+14) /* Memory Protection Extension */
> +#define X86_FEATURE_RDT		( 9*32+15) /* Resource Allocation */
>  #define X86_FEATURE_AVX512F	( 9*32+16) /* AVX-512 Foundation */
>  #define X86_FEATURE_RDSEED	( 9*32+18) /* The RDSEED instruction */
>  #define X86_FEATURE_ADX		( 9*32+19) /* The ADCX and ADOX instructions */
> @@ -248,6 +249,9 @@
>  /* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:1 (edx), word 12 */
>  #define X86_FEATURE_CQM_OCCUP_LLC (12*32+ 0) /* LLC occupancy monitoring if 1 */
>  
> +/* Intel-defined CPU features, CPUID level 0x00000010:0 (ebx), word 13 */
> +#define X86_FEATURE_CAT_L3	(13*32 + 1) /*Cache QOS Enforcement L3*/
					    ^^^^
Spaces between comment markers and text please.

> +
>  /*
>   * BUG word(s)
>   */
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 242ceed..81d95ac 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -114,6 +114,9 @@ struct cpuinfo_x86 {
>  	int			x86_cache_occ_scale;	/* scale to bytes */
>  	int			x86_power;
>  	unsigned long		loops_per_jiffy;
> +	/* Cache Allocation Technology values */
> +	int			x86_cat_cbmlength;
> +	int			x86_cat_closs;

Do I see it correctly, those two can be u16 each?

>  	/* cpuid returned max cores value: */
>  	u16			 x86_max_cores;
>  	u16			apicid;
> diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
> index 6c1ca13..6c91e39 100644
> --- a/arch/x86/kernel/cpu/Makefile
> +++ b/arch/x86/kernel/cpu/Makefile
> @@ -47,6 +47,7 @@ obj-$(CONFIG_PERF_EVENTS_INTEL_UNCORE)	+= perf_event_intel_uncore.o \
>  					   perf_event_intel_uncore_nhmex.o
>  endif
>  
> +obj-$(CONFIG_CGROUP_RDT) 		+=intel_rdt.o
>  
>  obj-$(CONFIG_X86_MCE)			+= mcheck/
>  obj-$(CONFIG_MTRR)			+= mtrr/
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 9b0fb70..c5ea1dd 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -668,6 +668,21 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
>  		}
>  	}
>  
> +	/* Additional Intel-defined flags: level 0x00000010 */
> +	if (c->cpuid_level >= 0x00000010) {
> +		u32 eax, ebx, ecx, edx;
> +
> +		cpuid_count(0x00000010, 0, &eax, &ebx, &ecx, &edx);
> +		c->x86_capability[13] = ebx;
> +
> +		if (cpu_has(c, X86_FEATURE_CAT_L3)) {
> +
> +			cpuid_count(0x00000010, 1, &eax, &ebx, &ecx, &edx);
> +			c->x86_cat_closs = (edx & 0xffff) + 1;
> +			c->x86_cat_cbmlength = (eax & 0xf) + 1;
> +		}
> +	}
> +
>  	/* AMD-defined flags: level 0x80000001 */
>  	xlvl = cpuid_eax(0x80000000);
>  	c->extended_cpuid_level = xlvl;
> diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
> new file mode 100644
> index 0000000..46ce449
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/intel_rdt.c
> @@ -0,0 +1,51 @@
> +/*
> + * Resource Director Technology(RDT) code
> + *
> + * Copyright (C) 2014 Intel Corporation
> + *
> + * 2014-09-10 Written by Vikas Shivappa
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * More information about RDT be found in the Intel (R) x86 Architecture
> + * Software Developer Manual, section 17.15.
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/slab.h>
> +#include <linux/err.h>
> +#include <linux/spinlock.h>
> +
> +static inline bool rdt_supported(struct cpuinfo_x86 *c)
> +{
> +	if (cpu_has(c, X86_FEATURE_RDT))
> +		return true;
> +
> +	return false;
> +}
> +
> +static int __init rdt_late_init(void)
> +{
> +	struct cpuinfo_x86 *c = &boot_cpu_data;
> +	int maxid, cbm_len;
> +
> +	if (!rdt_supported(c))

you can do cpu_has() directly here instead of the custom wrapper and
drop that rdt_supported() thing.

> +		return -ENODEV;
> +
> +	maxid = c->x86_cat_closs;
> +	cbm_len = c->x86_cat_cbmlength;

No need for those local variables, just use c->...

> +
> +	pr_info("cbmlength:%u,Closs: %u\n", cbm_len, maxid);

This text message needs to be much more user-friendly if it is going out
to the console unconditionally.

> +
> +	return 0;
> +}
> +
> +late_initcall(rdt_late_init);

Btw, this could all fit nicely in arch/x86/kernel/cpu/intel.c AFAICT
instead of adding a separate file and you probably don't even need the
late_initcall() even...

> diff --git a/init/Kconfig b/init/Kconfig
> index 9afb971..c5004b3 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -961,6 +961,17 @@ config CPUSETS
>  
>  	  Say N if unsure.
>  
> +config CGROUP_RDT
> +	bool "Resource Director Technology cgroup subsystem"
> +	depends on X86_64

depends on X86_64 && CPU_SUP_INTEL

Also, this should probably also depend on CGROUP-something or so
AFAICT...

> +	help
> +	  This option provides framework to allocate resources like
> +	  cache lines when applications fill cache.
> +	  This can be used by users to configure how much cache
> +	  that can be allocated to different applications.

This help text doesn't really help me if I'm Joe User.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--