linux-kernel - [tip: x86/cpu] x86/acpi/cstate: Optimize ARB

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:   Fri, 11 Nov 2022 17:50:02 -0000
From:   "tip-bot2 for Tony W Wang-oc" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Tony W Wang-oc" <TonyWWang-oc@...oxin.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/cpu] x86/acpi/cstate: Optimize ARB_DISABLE on Centaur CPUs

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

Commit-ID:     dacca1e5e75d7c1297f1334cdc10491dcdd1b2b8
Gitweb:        https://git.kernel.org/tip/dacca1e5e75d7c1297f1334cdc10491dcdd1b2b8
Author:        Tony W Wang-oc <TonyWWang-oc@...oxin.com>
AuthorDate:    Mon, 07 Nov 2022 11:34:49 +08:00
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Fri, 11 Nov 2022 09:42:05 -08:00

x86/acpi/cstate: Optimize ARB_DISABLE on Centaur CPUs

On all recent Centaur platforms, ARB_DISABLE is handled by PMU
automatically while entering C3 type state. No need for OS to
issue the ARB_DISABLE, so set bm_control to zero to indicate that.

Signed-off-by: Tony W Wang-oc <TonyWWang-oc@...oxin.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Link: https://lore.kernel.org/all/1667792089-4904-1-git-send-email-TonyWWang-oc%40zhaoxin.com
---
 arch/x86/kernel/acpi/cstate.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index 7945eae..401808b 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -52,17 +52,25 @@ void acpi_processor_power_init_bm_check(struct acpi_processor_flags *flags,
 	if (c->x86_vendor == X86_VENDOR_INTEL &&
 	    (c->x86 > 0xf || (c->x86 == 6 && c->x86_model >= 0x0f)))
 			flags->bm_control = 0;
-	/*
-	 * For all recent Centaur CPUs, the ucode will make sure that each
-	 * core can keep cache coherence with each other while entering C3
-	 * type state. So, set bm_check to 1 to indicate that the kernel
-	 * doesn't need to execute a cache flush operation (WBINVD) when
-	 * entering C3 type state.
-	 */
+
 	if (c->x86_vendor == X86_VENDOR_CENTAUR) {
 		if (c->x86 > 6 || (c->x86 == 6 && c->x86_model == 0x0f &&
-		    c->x86_stepping >= 0x0e))
+		    c->x86_stepping >= 0x0e)) {
+			/*
+			 * For all recent Centaur CPUs, the ucode will make sure that each
+			 * core can keep cache coherence with each other while entering C3
+			 * type state. So, set bm_check to 1 to indicate that the kernel
+			 * doesn't need to execute a cache flush operation (WBINVD) when
+			 * entering C3 type state.
+			 */
 			flags->bm_check = 1;
+			/*
+			 * For all recent Centaur platforms, ARB_DISABLE is a nop.
+			 * Set bm_control to zero to indicate that ARB_DISABLE is
+			 * not required while entering C3 type state.
+			 */
+			flags->bm_control = 0;
+		}
 	}
 
 	if (c->x86_vendor == X86_VENDOR_ZHAOXIN) {