Commit 147b9635 authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
Browse files

arm64: cpufeature: Fix feature comparison for CTR_EL0.{CWG,ERG} 



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: 3c739b57 ("arm64: Keep track of CPU feature registers")
Cc: <stable@vger.kernel.org> # 4.4.x-
Reviewed-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent a22c5cf5

arch/arm64/include/asm/cpufeature.h

+4 −3
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 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_HIGHER_OR_ZERO_SAFE,	/* Bigger value is safe, but 0 is biggest */

};



#define FTR_STRICT	true	/* SANITY check strict matching required */

arch/arm64/kernel/cpufeature.c

+6 −2
Original line number Diff line number Diff line
@@ -225,8 +225,8 @@ static const struct arm64_ftr_bits ftr_ctr[] = { 
	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, 31, 1, 1), /* RES1 */

	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_DIC_SHIFT, 1, 1),

	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_IDC_SHIFT, 1, 1),

	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_SAFE, CTR_CWG_SHIFT, 4, 0),

	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_SAFE, CTR_ERG_SHIFT, 4, 0),

	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, CTR_CWG_SHIFT, 4, 0),

	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, CTR_ERG_SHIFT, 4, 0),

	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
@@ -468,6 +468,10 @@ static s64 arm64_ftr_safe_value(const struct arm64_ftr_bits *ftrp, s64 new, 
	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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