Commit 8ba27ae3 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86_cache_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 cache resource control updates from Borislav Petkov:

 - add logic to correct MBM total and local values fixing errata SKX99
   and BDF102 (Fenghua Yu)

 - cleanups

* tag 'x86_cache_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/resctrl: Clean up unused function parameter in rmdir path
  x86/resctrl: Constify kernfs_ops
  x86/resctrl: Correct MBM total and local values
  Documentation/x86: Rename resctrl_ui.rst and add two errata to the file
parents 405f868f 19eb86a7

Documentation/x86/index.rst

+1 −1
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ x86-specific Documentation 
   pti

   mds

   microcode

   resctrl_ui

   resctrl

   tsx_async_abort

   usb-legacy-support

   i386/index

Documentation/x86/resctrl_ui.rst→Documentation/x86/resctrl.rst

+93 −0
Original line number Diff line number Diff line
@@ -1209,3 +1209,96 @@ View the llc occupancy snapshot:: 


  # cat /sys/fs/resctrl/p1/mon_data/mon_L3_00/llc_occupancy

  11234000



Intel RDT Errata

================



Intel MBM Counters May Report System Memory Bandwidth Incorrectly

-----------------------------------------------------------------



Errata SKX99 for Skylake server and BDF102 for Broadwell server.



Problem: Intel Memory Bandwidth Monitoring (MBM) counters track metrics

according to the assigned Resource Monitor ID (RMID) for that logical

core. The IA32_QM_CTR register (MSR 0xC8E), used to report these

metrics, may report incorrect system bandwidth for certain RMID values.



Implication: Due to the errata, system memory bandwidth may not match

what is reported.



Workaround: MBM total and local readings are corrected according to the

following correction factor table:



+---------------+---------------+---------------+-----------------+

|core count	|rmid count	|rmid threshold	|correction factor|

+---------------+---------------+---------------+-----------------+

|1		|8		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|2		|16		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|3		|24		|15		|0.969650	  |

+---------------+---------------+---------------+-----------------+

|4		|32		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|6		|48		|31		|0.969650	  |

+---------------+---------------+---------------+-----------------+

|7		|56		|47		|1.142857	  |

+---------------+---------------+---------------+-----------------+

|8		|64		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|9		|72		|63		|1.185115	  |

+---------------+---------------+---------------+-----------------+

|10		|80		|63		|1.066553	  |

+---------------+---------------+---------------+-----------------+

|11		|88		|79		|1.454545	  |

+---------------+---------------+---------------+-----------------+

|12		|96		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|13		|104		|95		|1.230769	  |

+---------------+---------------+---------------+-----------------+

|14		|112		|95		|1.142857	  |

+---------------+---------------+---------------+-----------------+

|15		|120		|95		|1.066667	  |

+---------------+---------------+---------------+-----------------+

|16		|128		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|17		|136		|127		|1.254863	  |

+---------------+---------------+---------------+-----------------+

|18		|144		|127		|1.185255	  |

+---------------+---------------+---------------+-----------------+

|19		|152		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|20		|160		|127		|1.066667	  |

+---------------+---------------+---------------+-----------------+

|21		|168		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|22		|176		|159		|1.454334	  |

+---------------+---------------+---------------+-----------------+

|23		|184		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|24		|192		|127		|0.969744	  |

+---------------+---------------+---------------+-----------------+

|25		|200		|191		|1.280246	  |

+---------------+---------------+---------------+-----------------+

|26		|208		|191		|1.230921	  |

+---------------+---------------+---------------+-----------------+

|27		|216		|0		|1.000000	  |

+---------------+---------------+---------------+-----------------+

|28		|224		|191		|1.143118	  |

+---------------+---------------+---------------+-----------------+



If rmid > rmid threshold, MBM total and local values should be multiplied

by the correction factor.



See:



1. Erratum SKX99 in Intel Xeon Processor Scalable Family Specification Update:

http://web.archive.org/web/20200716124958/https://www.intel.com/content/www/us/en/processors/xeon/scalable/xeon-scalable-spec-update.html



2. Erratum BDF102 in Intel Xeon E5-2600 v4 Processor Product Family Specification Update:

http://web.archive.org/web/20191125200531/https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-v4-spec-update.pdf



3. The errata in Intel Resource Director Technology (Intel RDT) on 2nd Generation Intel Xeon Scalable Processors Reference Manual:

https://software.intel.com/content/www/us/en/develop/articles/intel-resource-director-technology-rdt-reference-manual.html



for further information.

arch/x86/kernel/cpu/resctrl/core.c

+4 −0
Original line number Diff line number Diff line
@@ -895,6 +895,10 @@ static __init void __check_quirks_intel(void) 
			set_rdt_options("!cmt,!mbmtotal,!mbmlocal,!l3cat");

		else

			set_rdt_options("!l3cat");

		fallthrough;

	case INTEL_FAM6_BROADWELL_X:

		intel_rdt_mbm_apply_quirk();

		break;

	}

}

arch/x86/kernel/cpu/resctrl/internal.h

+2 −1
Original line number Diff line number Diff line
@@ -264,7 +264,7 @@ void __exit rdtgroup_exit(void); 
struct rftype {

	char			*name;

	umode_t			mode;

	struct kernfs_ops	*kf_ops;

	const struct kernfs_ops	*kf_ops;

	unsigned long		flags;

	unsigned long		fflags;
@@ -619,6 +619,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r, 
void mbm_setup_overflow_handler(struct rdt_domain *dom,

				unsigned long delay_ms);

void mbm_handle_overflow(struct work_struct *work);

void __init intel_rdt_mbm_apply_quirk(void);

bool is_mba_sc(struct rdt_resource *r);

void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm);

u32 delay_bw_map(unsigned long bw, struct rdt_resource *r);

arch/x86/kernel/cpu/resctrl/monitor.c

+80 −2
Original line number Diff line number Diff line
@@ -64,6 +64,69 @@ unsigned int rdt_mon_features; 
 */

unsigned int resctrl_cqm_threshold;



#define CF(cf)	((unsigned long)(1048576 * (cf) + 0.5))



/*

 * The correction factor table is documented in Documentation/x86/resctrl.rst.

 * If rmid > rmid threshold, MBM total and local values should be multiplied

 * by the correction factor.

 *

 * The original table is modified for better code:

 *

 * 1. The threshold 0 is changed to rmid count - 1 so don't do correction

 *    for the case.

 * 2. MBM total and local correction table indexed by core counter which is

 *    equal to (x86_cache_max_rmid + 1) / 8 - 1 and is from 0 up to 27.

 * 3. The correction factor is normalized to 2^20 (1048576) so it's faster

 *    to calculate corrected value by shifting:

 *    corrected_value = (original_value * correction_factor) >> 20

 */

static const struct mbm_correction_factor_table {

	u32 rmidthreshold;

	u64 cf;

} mbm_cf_table[] __initdata = {

	{7,	CF(1.000000)},

	{15,	CF(1.000000)},

	{15,	CF(0.969650)},

	{31,	CF(1.000000)},

	{31,	CF(1.066667)},

	{31,	CF(0.969650)},

	{47,	CF(1.142857)},

	{63,	CF(1.000000)},

	{63,	CF(1.185115)},

	{63,	CF(1.066553)},

	{79,	CF(1.454545)},

	{95,	CF(1.000000)},

	{95,	CF(1.230769)},

	{95,	CF(1.142857)},

	{95,	CF(1.066667)},

	{127,	CF(1.000000)},

	{127,	CF(1.254863)},

	{127,	CF(1.185255)},

	{151,	CF(1.000000)},

	{127,	CF(1.066667)},

	{167,	CF(1.000000)},

	{159,	CF(1.454334)},

	{183,	CF(1.000000)},

	{127,	CF(0.969744)},

	{191,	CF(1.280246)},

	{191,	CF(1.230921)},

	{215,	CF(1.000000)},

	{191,	CF(1.143118)},

};



static u32 mbm_cf_rmidthreshold __read_mostly = UINT_MAX;

static u64 mbm_cf __read_mostly;



static inline u64 get_corrected_mbm_count(u32 rmid, unsigned long val)

{

	/* Correct MBM value. */

	if (rmid > mbm_cf_rmidthreshold)

		val = (val * mbm_cf) >> 20;



	return val;

}



static inline struct rmid_entry *__rmid_entry(u32 rmid)

{

	struct rmid_entry *entry;
@@ -260,7 +323,8 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr) 
	m->chunks += chunks;

	m->prev_msr = tval;



	rr->val += m->chunks;

	rr->val += get_corrected_mbm_count(rmid, m->chunks);



	return 0;

}
@@ -279,7 +343,7 @@ static void mbm_bw_count(u32 rmid, struct rmid_read *rr) 
		return;



	chunks = mbm_overflow_count(m->prev_bw_msr, tval, rr->r->mbm_width);

	cur_bw = (chunks * r->mon_scale) >> 20;

	cur_bw = (get_corrected_mbm_count(rmid, chunks) * r->mon_scale) >> 20;



	if (m->delta_comp)

		m->delta_bw = abs(cur_bw - m->prev_bw);
@@ -642,3 +706,17 @@ int rdt_get_mon_l3_config(struct rdt_resource *r) 


	return 0;

}



void __init intel_rdt_mbm_apply_quirk(void)

{

	int cf_index;



	cf_index = (boot_cpu_data.x86_cache_max_rmid + 1) / 8 - 1;

	if (cf_index >= ARRAY_SIZE(mbm_cf_table)) {

		pr_info("No MBM correction factor available\n");

		return;

	}



	mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;

	mbm_cf = mbm_cf_table[cf_index].cf;

}