linux-kernel - [tip: x86/cache] x86/resctrl: Make prefetch_disable

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Message-ID: <174180002117.14745.15433290797717039575.tip-bot2@tip-bot2>
Date: Wed, 12 Mar 2025 17:20:21 -0000
From: "tip-bot2 for James Morse" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: James Morse <james.morse@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>,
 Shaopeng Tan <tan.shaopeng@...fujitsu.com>, Tony Luck <tony.luck@...el.com>,
 Reinette Chatre <reinette.chatre@...el.com>, Fenghua Yu <fenghuay@...dia.com>,
 Babu Moger <babu.moger@....com>, Carl Worth <carl@...amperecomputing.com>,
 Peter Newman <peternewman@...gle.com>,
 Amit Singh Tomar <amitsinght@...vell.com>,
 Shanker Donthineni <sdonthineni@...dia.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/cache] x86/resctrl: Make prefetch_disable_bits belong to
 the arch code

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

Commit-ID:     4d20f38ab6d922dd6b8a33795b6e72516d733eb2
Gitweb:        https://git.kernel.org/tip/4d20f38ab6d922dd6b8a33795b6e72516d733eb2
Author:        James Morse <james.morse@....com>
AuthorDate:    Tue, 11 Mar 2025 18:37:10 
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Wed, 12 Mar 2025 12:24:30 +01:00

x86/resctrl: Make prefetch_disable_bits belong to the arch code

prefetch_disable_bits is set by rdtgroup_locksetup_enter() from a value
provided by the architecture, but is largely read by other architecture
helpers.

Make resctrl_arch_get_prefetch_disable_bits() set prefetch_disable_bits so
that it can be isolated to arch-code from where the other arch-code helpers
can use its cached value.

Signed-off-by: James Morse <james.morse@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Reviewed-by: Fenghua Yu <fenghuay@...dia.com>
Reviewed-by: Babu Moger <babu.moger@....com>
Tested-by: Carl Worth <carl@...amperecomputing.com> # arm64
Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Tested-by: Peter Newman <peternewman@...gle.com>
Tested-by: Amit Singh Tomar <amitsinght@...vell.com> # arm64
Tested-by: Shanker Donthineni <sdonthineni@...dia.com> # arm64
Tested-by: Babu Moger <babu.moger@....com>
Link: https://lore.kernel.org/r/20250311183715.16445-26-james.morse@arm.com
---
 arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
index 1f42c11..90044a0 100644
--- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
+++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
@@ -84,6 +84,8 @@ static const struct class pseudo_lock_class = {
  */
 u64 resctrl_arch_get_prefetch_disable_bits(void)
 {
+	prefetch_disable_bits = 0;
+
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
 	    boot_cpu_data.x86 != 6)
 		return 0;
@@ -99,7 +101,8 @@ u64 resctrl_arch_get_prefetch_disable_bits(void)
 		 * 3    DCU IP Prefetcher Disable (R/W)
 		 * 63:4 Reserved
 		 */
-		return 0xF;
+		prefetch_disable_bits = 0xF;
+		break;
 	case INTEL_ATOM_GOLDMONT:
 	case INTEL_ATOM_GOLDMONT_PLUS:
 		/*
@@ -110,10 +113,11 @@ u64 resctrl_arch_get_prefetch_disable_bits(void)
 		 * 2     DCU Hardware Prefetcher Disable (R/W)
 		 * 63:3  Reserved
 		 */
-		return 0x5;
+		prefetch_disable_bits = 0x5;
+		break;
 	}
 
-	return 0;
+	return prefetch_disable_bits;
 }
 
 /**
@@ -713,8 +717,7 @@ int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp)
 	 * Not knowing the bits to disable prefetching implies that this
 	 * platform does not support Cache Pseudo-Locking.
 	 */
-	prefetch_disable_bits = resctrl_arch_get_prefetch_disable_bits();
-	if (prefetch_disable_bits == 0) {
+	if (resctrl_arch_get_prefetch_disable_bits() == 0) {
 		rdt_last_cmd_puts("Pseudo-locking not supported\n");
 		return -EINVAL;
 	}