Commit b389d799 authored Jan 09, 2017 by Mark Rutland Committed by Will Deacon Jan 10, 2017

arm64: cpufeature: treat unknown fields as RES0



Any fields not defined in an arm64_ftr_bits entry are propagated to the
system-wide register value in init_cpu_ftr_reg(), and while we require
that these strictly match for the sanity checks, we don't update them in
update_cpu_ftr_reg().

Generally, the lack of an arm64_ftr_bits entry indicates that the bits
are currently RES0 (as is the case for the upper 32 bits of all
supposedly 32-bit registers).

A better default would be to use zero for the system-wide value of
unallocated bits, making all register checking consistent, and allowing
for subsequent simplifications to the arm64_ftr_bits arrays.

This patch updates init_cpu_ftr_reg() to treat unallocated bits as RES0
for the purpose of the system-wide safe value. These bits will still be
sanity checked with strict match requirements, as is currently the case.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent f31deaad

arch/arm64/kernel/cpufeature.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -415,23 +415,33 @@ static void __init sort_ftr_regs(void)
		/*
		* Initialise the CPU feature register from Boot CPU values.
		* Also initiliases the strict_mask for the register.
		* Any bits that are not covered by an arm64_ftr_bits entry are considered
		* RES0 for the system-wide value, and must strictly match.
		*/
		static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
		{
		u64 val = 0;
		u64 strict_mask = ~0x0ULL;
		u64 valid_mask = 0;

		const struct arm64_ftr_bits *ftrp;
		struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);

		BUG_ON(!reg);

		for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
		u64 ftr_mask = arm64_ftr_mask(ftrp);
		s64 ftr_new = arm64_ftr_value(ftrp, new);

		val = arm64_ftr_set_value(ftrp, val, ftr_new);

		valid_mask \|= ftr_mask;
		if (!ftrp->strict)
		strict_mask &= ~arm64_ftr_mask(ftrp);
		strict_mask &= ~ftr_mask;
		}

		val &= valid_mask;

		reg->sys_val = val;
		reg->strict_mask = strict_mask;
		}

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