linux-kernel - [PATCH v4 12/22] arm64: capabilities: Introduce weak features based on local CPU

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

Message-Id: <20180313115120.17256-13-suzuki.poulose@arm.com>
Date:   Tue, 13 Mar 2018 11:51:10 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, will.deacon@....com,
        dave.martin@....com, catalin.marinas@....com, marc.zyngier@....com,
        mark.rutland@....com, ard.biesheuvel@...aro.org,
        jnair@...iumnetworks.com, ckadabi@...eaurora.org,
        robin.murphy@....com, shankerd@...eaurora.org,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH v4 12/22] arm64: capabilities: Introduce weak features based on local CPU

Now that we have the flexibility of defining system features based
on individual CPUs, introduce CPU feature type that can be detected
on a local SCOPE and ignores the conflict on late CPUs. This is
applicable for ARM64_HAS_NO_HW_PREFETCH, where it is fine for
the system to have CPUs without hardware prefetch turning up
later. We only suffer a performance penalty, nothing fatal.

Cc: Will Deacon <will.deacon@....com>
Reviewed-by: Dave Martin <dave.martin@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 arch/arm64/include/asm/cpufeature.h | 8 ++++++++
 arch/arm64/kernel/cpufeature.c      | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index c187b926daf9..effb1c038221 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -239,6 +239,14 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
  */
 #define ARM64_CPUCAP_SYSTEM_FEATURE	\
 	(ARM64_CPUCAP_SCOPE_SYSTEM | ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU)
+/*
+ * CPU feature detected at boot time based on feature of one or more CPUs.
+ * All possible conflicts for a late CPU are ignored.
+ */
+#define ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE		\
+	(ARM64_CPUCAP_SCOPE_LOCAL_CPU		|	\
+	 ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU	|	\
+	 ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU)
 
 struct arm64_cpu_capabilities {
 	const char *desc;
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index fc6164bc9ef4..0955e02fa638 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1007,7 +1007,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 	{
 		.desc = "Software prefetching using PRFM",
 		.capability = ARM64_HAS_NO_HW_PREFETCH,
-		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
 		.matches = has_no_hw_prefetch,
 	},
 #ifdef CONFIG_ARM64_UAO
-- 
2.14.3