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Subject[PATCH 4.14 05/33] arm64: cpufeature: Fix feature comparison for CTR_EL0.{CWG,ERG}
Date
From: Will Deacon <will@kernel.org>

commit 147b9635e6347104b91f48ca9dca61eb0fbf2a54 upstream.

If CTR_EL0.{CWG,ERG} are 0b0000 then they must be interpreted to have
their architecturally maximum values, which defeats the use of
FTR_HIGHER_SAFE when sanitising CPU ID registers on heterogeneous
machines.

Introduce FTR_HIGHER_OR_ZERO_SAFE so that these fields effectively
saturate at zero.

Fixes: 3c739b571084 ("arm64: Keep track of CPU feature registers")
Cc: <stable@vger.kernel.org> # 4.4.x-
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm64/include/asm/cpufeature.h | 7 ++++---
arch/arm64/kernel/cpufeature.c | 8 ++++++--
2 files changed, 10 insertions(+), 5 deletions(-)

--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -44,9 +44,10 @@
*/

enum ftr_type {
- FTR_EXACT, /* Use a predefined safe value */
- FTR_LOWER_SAFE, /* Smaller value is safe */
- FTR_HIGHER_SAFE,/* Bigger value is safe */
+ FTR_EXACT, /* Use a predefined safe value */
+ FTR_LOWER_SAFE, /* Smaller value is safe */
+ FTR_HIGHER_SAFE, /* Bigger value is safe */
+ FTR_HIGHER_OR_ZERO_SAFE, /* Bigger value is safe, but 0 is biggest */
};

#define FTR_STRICT true /* SANITY check strict matching required */
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -178,8 +178,8 @@ static const struct arm64_ftr_bits ftr_c
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, 31, 1, 1), /* RES1 */
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, 29, 1, 1), /* DIC */
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, 28, 1, 1), /* IDC */
- ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_SAFE, 24, 4, 0), /* CWG */
- ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_SAFE, 20, 4, 0), /* ERG */
+ ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, 24, 4, 0), /* CWG */
+ ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, 20, 4, 0), /* ERG */
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_DMINLINE_SHIFT, 4, 1),
/*
* Linux can handle differing I-cache policies. Userspace JITs will
@@ -411,6 +411,10 @@ static s64 arm64_ftr_safe_value(const st
case FTR_LOWER_SAFE:
ret = new < cur ? new : cur;
break;
+ case FTR_HIGHER_OR_ZERO_SAFE:
+ if (!cur || !new)
+ break;
+ /* Fallthrough */
case FTR_HIGHER_SAFE:
ret = new > cur ? new : cur;
break;

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