5.4-stable review patch. If anyone has any objections, please let me know.
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From: James Morse james.morse@arm.com
[ 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@arm.com Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com Link: https://lore.kernel.org/r/20220909165938.3931307-2-james.morse@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com [ Mark: fixup lack of 'width' parameter ] Signed-off-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/cpufeature.c | 36 +++++++++++++++++++++++++++------- 1 file changed, 29 insertions(+), 7 deletions(-)
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, \