linux-kernel - [PATCH 01/15] x86/resctrl: Remove hard-coded memory bandwidth limit

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Message-ID: <20231201005720.235639-2-babu.moger@amd.com>
Date:   Thu, 30 Nov 2023 18:57:06 -0600
From:   Babu Moger <babu.moger@....com>
To:     <corbet@....net>, <fenghua.yu@...el.com>,
        <reinette.chatre@...el.com>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC:     <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
        <seanjc@...gle.com>, <kim.phillips@....com>, <babu.moger@....com>,
        <jmattson@...gle.com>, <ilpo.jarvinen@...ux.intel.com>,
        <jithu.joseph@...el.com>, <kan.liang@...ux.intel.com>,
        <nikunj@....com>, <daniel.sneddon@...ux.intel.com>,
        <pbonzini@...hat.com>, <rick.p.edgecombe@...el.com>,
        <rppt@...nel.org>, <maciej.wieczor-retman@...el.com>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <eranian@...gle.com>, <peternewman@...gle.com>, <dhagiani@....com>
Subject: [PATCH 01/15] x86/resctrl: Remove hard-coded memory bandwidth limit

The QOS Memory Bandwidth Enforcement Limit is reported by
CPUID_Fn80000020_EAX_x01.
Bits Description
31:0 BW_LEN: Size of the QOS Memory Bandwidth Enforcement Limit.

Remove the hardcoded bandwidth limit value and detect using CPUID command.

The CPUID details are documentation in the PPR listed below [1].
[1] Processor Programming Reference (PPR) Vol 1.1 for AMD Family 19h Model
11h B1 - 55901 Rev 0.25.

Fixes: 4d05bf71f157 ("x86/resctrl: Introduce AMD QOS feature")
Signed-off-by: Babu Moger <babu.moger@....com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
---
 arch/x86/kernel/cpu/resctrl/core.c     | 2 +-
 arch/x86/kernel/cpu/resctrl/internal.h | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 19e0681f0435..3fbae10b662d 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -243,7 +243,7 @@ static bool __rdt_get_mem_config_amd(struct rdt_resource *r)
 
 	cpuid_count(0x80000020, subleaf, &eax.full, &ebx, &ecx, &edx.full);
 	hw_res->num_closid = edx.split.cos_max + 1;
-	r->default_ctrl = MAX_MBA_BW_AMD;
+	r->default_ctrl = 1 << eax.full;
 
 	/* AMD does not use delay */
 	r->membw.delay_linear = false;
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index a4f1aa15f0a2..d2979748fae4 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -18,7 +18,6 @@
 #define MBM_OVERFLOW_INTERVAL		1000
 #define MAX_MBA_BW			100u
 #define MBA_IS_LINEAR			0x4
-#define MAX_MBA_BW_AMD			0x800
 #define MBM_CNTR_WIDTH_OFFSET_AMD	20
 
 #define RMID_VAL_ERROR			BIT_ULL(63)
-- 
2.34.1