For performance analysis it may be desirable to disable MTE altogether
via an early param. Introduce arm64.mte_disable and, if true, filter out
the sanitised ID_AA64PFR1_EL1.MTE field to avoid exposing the HWCAP to
user.
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
---
Notes:
New in v4.
Documentation/admin-guide/kernel-parameters.txt | 4 ++++
arch/arm64/kernel/cpufeature.c | 11 +++++++++++
2 files changed, 15 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f2a93c8679e8..7436e7462b85 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -373,6 +373,10 @@
arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
Format: <io>,<irq>,<nodeID>
+ arm64.mte_disable=
+ [ARM64] Disable Linux support for the Memory
+ Tagging Extension (both user and in-kernel).
+
ataflop= [HW,M68k]
atarimouse= [HW,MOUSE] Atari Mouse
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index aaadc1cbc006..f7596830694f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -126,12 +126,23 @@ static void cpu_enable_cnp(struct arm64_cpu_capabilities const *cap);
static bool __system_matches_cap(unsigned int n);
#ifdef CONFIG_ARM64_MTE
+static bool mte_disable;
+
+static int __init arm64_mte_disable(char *buf)
+{
+ return strtobool(buf, &mte_disable);
+}
+early_param("arm64.mte_disable", arm64_mte_disable);
+
s64 mte_ftr_filter(const struct arm64_ftr_bits *ftrp, s64 val)
{
struct device_node *np;
static bool memory_checked = false;
static bool mte_capable = true;
+ if (mte_disable)
+ return ID_AA64PFR1_MTE_NI;
+
/* EL0-only MTE is not supported by Linux, don't expose it */
if (val < ID_AA64PFR1_MTE)
return ID_AA64PFR1_MTE_NI;
