linux-kernel - [tip: x86/urgent] x86/resctrl: Fix min_cbm

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Date:   Tue, 18 Oct 2022 18:33:25 -0000
From:   "tip-bot2 for Babu Moger" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        Babu Moger <babu.moger@....com>, Borislav Petkov <bp@...e.de>,
        Ingo Molnar <mingo@...nel.org>,
        James Morse <james.morse@....com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>, <stable@...r.kernel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/resctrl: Fix min_cbm_bits for AMD

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     67bf6493449b09590f9f71d7df29efb392b12d25
Gitweb:        https://git.kernel.org/tip/67bf6493449b09590f9f71d7df29efb392b12d25
Author:        Babu Moger <babu.moger@....com>
AuthorDate:    Tue, 27 Sep 2022 15:16:29 -05:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Tue, 18 Oct 2022 20:25:16 +02:00

x86/resctrl: Fix min_cbm_bits for AMD

AMD systems support zero CBM (capacity bit mask) for cache allocation.
That is reflected in rdt_init_res_defs_amd() by:

  r->cache.arch_has_empty_bitmaps = true;

However given the unified code in cbm_validate(), checking for:

  val == 0 && !arch_has_empty_bitmaps

is not enough because of another check in cbm_validate():

  if ((zero_bit - first_bit) < r->cache.min_cbm_bits)

The default value of r->cache.min_cbm_bits = 1.

Leading to:

  $ cd /sys/fs/resctrl
  $ mkdir foo
  $ cd foo
  $ echo L3:0=0 > schemata
    -bash: echo: write error: Invalid argument
  $ cat /sys/fs/resctrl/info/last_cmd_status
    Need at least 1 bits in the mask

Initialize the min_cbm_bits to 0 for AMD. Also, remove the default
setting of min_cbm_bits and initialize it separately.

After the fix:

  $ cd /sys/fs/resctrl
  $ mkdir foo
  $ cd foo
  $ echo L3:0=0 > schemata
  $ cat /sys/fs/resctrl/info/last_cmd_status
    ok

Fixes: 316e7f901f5a ("x86/resctrl: Add struct rdt_cache::arch_has_{sparse, empty}_bitmaps")
Co-developed-by: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Babu Moger <babu.moger@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: James Morse <james.morse@....com>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
Cc: <stable@...r.kernel.org>
Link: https://lore.kernel.org/lkml/20220517001234.3137157-1-eranian@google.com
---
 arch/x86/kernel/cpu/resctrl/core.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index de62b0b..3266ea3 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -66,9 +66,6 @@ struct rdt_hw_resource rdt_resources_all[] = {
 			.rid			= RDT_RESOURCE_L3,
 			.name			= "L3",
 			.cache_level		= 3,
-			.cache = {
-				.min_cbm_bits	= 1,
-			},
 			.domains		= domain_init(RDT_RESOURCE_L3),
 			.parse_ctrlval		= parse_cbm,
 			.format_str		= "%d=%0*x",
@@ -83,9 +80,6 @@ struct rdt_hw_resource rdt_resources_all[] = {
 			.rid			= RDT_RESOURCE_L2,
 			.name			= "L2",
 			.cache_level		= 2,
-			.cache = {
-				.min_cbm_bits	= 1,
-			},
 			.domains		= domain_init(RDT_RESOURCE_L2),
 			.parse_ctrlval		= parse_cbm,
 			.format_str		= "%d=%0*x",
@@ -836,6 +830,7 @@ static __init void rdt_init_res_defs_intel(void)
 			r->cache.arch_has_sparse_bitmaps = false;
 			r->cache.arch_has_empty_bitmaps = false;
 			r->cache.arch_has_per_cpu_cfg = false;
+			r->cache.min_cbm_bits = 1;
 		} else if (r->rid == RDT_RESOURCE_MBA) {
 			hw_res->msr_base = MSR_IA32_MBA_THRTL_BASE;
 			hw_res->msr_update = mba_wrmsr_intel;
@@ -856,6 +851,7 @@ static __init void rdt_init_res_defs_amd(void)
 			r->cache.arch_has_sparse_bitmaps = true;
 			r->cache.arch_has_empty_bitmaps = true;
 			r->cache.arch_has_per_cpu_cfg = true;
+			r->cache.min_cbm_bits = 0;
 		} else if (r->rid == RDT_RESOURCE_MBA) {
 			hw_res->msr_base = MSR_IA32_MBA_BW_BASE;
 			hw_res->msr_update = mba_wrmsr_amd;