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Commit ebb9ffd1 authored by Will Deacon's avatar Will Deacon Committed by Greg Kroah-Hartman
Browse files

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



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: 3c739b57 ("arm64: Keep track of CPU feature registers")
Cc: <stable@vger.kernel.org> # 4.4.y only
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>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 375dddef

arch/arm64/include/asm/cpufeature.h

+4 −3
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ 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
@@ -130,8 +130,8 @@ static struct arm64_ftr_bits ftr_ctr[] = { 
	ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, 30, 1, 0),

	U_ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, 29, 1, 1),	/* DIC */

	U_ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, 28, 1, 1),	/* IDC */

	U_ARM64_FTR_BITS(FTR_STRICT, FTR_HIGHER_SAFE, 24, 4, 0),	/* CWG */

	U_ARM64_FTR_BITS(FTR_STRICT, FTR_HIGHER_SAFE, 20, 4, 0),	/* ERG */

	U_ARM64_FTR_BITS(FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, 24, 4, 0),	/* CWG */

	U_ARM64_FTR_BITS(FTR_STRICT, FTR_HIGHER_OR_ZERO_SAFE, 20, 4, 0),	/* ERG */

	U_ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, 16, 4, 1),	/* DminLine */

	/*

	 * Linux can handle differing I-cache policies. Userspace JITs will
@@ -341,6 +341,10 @@ static s64 arm64_ftr_safe_value(struct arm64_ftr_bits *ftrp, s64 new, s64 cur) 
	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;