This is a note to let you know that I've just added the patch titled
arm64: cpufeature: Force HWCAP to be based on the sysreg visible to user-space
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-cpufeature-force-hwcap-to-be-based-on-the-sysr.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6609ac4888b2d601fe76555f6030849604bc0370
Author: James Morse <james.morse@xxxxxxx>
Date: Fri Aug 9 11:34:14 2024 +0100
arm64: cpufeature: Force HWCAP to be based on the sysreg visible to user-space
[ Upstream commit 237405ebef580a7352a52129b2465c117145eafa ]
arm64 advertises hardware features to user-space via HWCAPs, and by
emulating access to the CPUs id registers. The cpufeature code has a
sanitised system-wide view of an id register, and a sanitised user-space
view of an id register, where some features use their 'safe' value
instead of the hardware value.
It is currently possible for a HWCAP to be advertised where the user-space
view of the id register does not show the feature as supported.
Erratum workaround need to remove both the HWCAP, and the feature from
the user-space view of the id register. This involves duplicating the
code, and spreading it over cpufeature.c and cpu_errata.c.
Make the HWCAP code use the user-space view of id registers. This ensures
the values never diverge, and allows erratum workaround to remove HWCAP
by modifying the user-space view of the id register.
Signed-off-by: James Morse <james.morse@xxxxxxx>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Link: https://lore.kernel.org/r/20220909165938.3931307-2-james.morse@xxxxxxx
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
[ Mark: fixup lack of 'width' parameter ]
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 396d96224b48b..e4f426c4f2428 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -875,17 +875,39 @@ feature_matches(u64 reg, const struct arm64_cpu_capabilities *entry)
return val >= entry->min_field_value;
}
-static bool
-has_cpuid_feature(const struct arm64_cpu_capabilities *entry, int scope)
+static u64
+read_scoped_sysreg(const struct arm64_cpu_capabilities *entry, int scope)
{
- u64 val;
-
WARN_ON(scope == SCOPE_LOCAL_CPU && preemptible());
if (scope == SCOPE_SYSTEM)
- val = read_sanitised_ftr_reg(entry->sys_reg);
+ return read_sanitised_ftr_reg(entry->sys_reg);
else
- val = __read_sysreg_by_encoding(entry->sys_reg);
+ return __read_sysreg_by_encoding(entry->sys_reg);
+}
+static bool
+has_user_cpuid_feature(const struct arm64_cpu_capabilities *entry, int scope)
+{
+ int mask;
+ struct arm64_ftr_reg *regp;
+ u64 val = read_scoped_sysreg(entry, scope);
+
+ regp = get_arm64_ftr_reg(entry->sys_reg);
+ if (!regp)
+ return false;
+
+ mask = cpuid_feature_extract_unsigned_field(regp->user_mask,
+ entry->field_pos);
+ if (!mask)
+ return false;
+
+ return feature_matches(val, entry);
+}
+
+static bool
+has_cpuid_feature(const struct arm64_cpu_capabilities *entry, int scope)
+{
+ u64 val = read_scoped_sysreg(entry, scope);
return feature_matches(val, entry);
}
@@ -1593,7 +1615,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
};
#define HWCAP_CPUID_MATCH(reg, field, s, min_value) \
- .matches = has_cpuid_feature, \
+ .matches = has_user_cpuid_feature, \
.sys_reg = reg, \
.field_pos = field, \
.sign = s, \
