Commit 7f632d33 authored by Mark Rutland's avatar Mark Rutland Committed by Catalin Marinas
Browse files

arm64: Fixup user features at boot time 



For ARM64_WORKAROUND_2658417, we use a cpu_enable() callback to hide the
ID_AA64ISAR1_EL1.BF16 ID register field. This is a little awkward as
CPUs may attempt to apply the workaround concurrently, requiring that we
protect the bulk of the callback with a raw_spinlock, and requiring some
pointless work every time a CPU is subsequently hotplugged in.

This patch makes this a little simpler by handling the masking once at
boot time. A new user_feature_fixup() function is called at the start of
setup_user_features() to mask the feature, matching the style of
elf_hwcap_fixup(). The ARM64_WORKAROUND_2658417 cpucap is added to
cpucap_is_possible() so that code can be elided entirely when this is
not possible.

Note that the ARM64_WORKAROUND_2658417 capability is matched with
ERRATA_MIDR_RANGE(), which implicitly gives the capability a
ARM64_CPUCAP_LOCAL_CPU_ERRATUM type, which forbids the late onlining of
a CPU with the erratum if the erratum was not present at boot time.
Therefore this patch doesn't change the behaviour for late onlining.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 075f48c9

arch/arm64/include/asm/cpucaps.h

+2 −0
Original line number Diff line number Diff line
@@ -40,6 +40,8 @@ cpucap_is_possible(const unsigned int cap) 
		return IS_ENABLED(CONFIG_ARM64_BTI);

	case ARM64_HAS_TLB_RANGE:

		return IS_ENABLED(CONFIG_ARM64_TLB_RANGE);

	case ARM64_WORKAROUND_2658417:

		return IS_ENABLED(CONFIG_ARM64_ERRATUM_2658417);

	}



	return true;

arch/arm64/kernel/cpu_errata.c

+0 −17
Original line number Diff line number Diff line
@@ -121,22 +121,6 @@ cpu_enable_cache_maint_trap(const struct arm64_cpu_capabilities *__unused) 
	sysreg_clear_set(sctlr_el1, SCTLR_EL1_UCI, 0);

}



static DEFINE_RAW_SPINLOCK(reg_user_mask_modification);

static void __maybe_unused

cpu_clear_bf16_from_user_emulation(const struct arm64_cpu_capabilities *__unused)

{

	struct arm64_ftr_reg *regp;



	regp = get_arm64_ftr_reg(SYS_ID_AA64ISAR1_EL1);

	if (!regp)

		return;



	raw_spin_lock(&reg_user_mask_modification);

	if (regp->user_mask & ID_AA64ISAR1_EL1_BF16_MASK)

		regp->user_mask &= ~ID_AA64ISAR1_EL1_BF16_MASK;

	raw_spin_unlock(&reg_user_mask_modification);

}



#define CAP_MIDR_RANGE(model, v_min, r_min, v_max, r_max)	\

	.matches = is_affected_midr_range,			\

	.midr_range = MIDR_RANGE(model, v_min, r_min, v_max, r_max)
@@ -727,7 +711,6 @@ const struct arm64_cpu_capabilities arm64_errata[] = { 
		/* Cortex-A510 r0p0 - r1p1 */

		ERRATA_MIDR_RANGE(MIDR_CORTEX_A510, 0, 0, 1, 1),

		MIDR_FIXED(MIDR_CPU_VAR_REV(1,1), BIT(25)),

		.cpu_enable = cpu_clear_bf16_from_user_emulation,

	},

#endif

#ifdef CONFIG_AMPERE_ERRATUM_AC03_CPU_38

arch/arm64/kernel/cpufeature.c

+13 −0
Original line number Diff line number Diff line
@@ -2190,6 +2190,17 @@ static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) 
}

#endif /* CONFIG_ARM64_MTE */



static void user_feature_fixup(void)

{

	if (cpus_have_cap(ARM64_WORKAROUND_2658417)) {

		struct arm64_ftr_reg *regp;



		regp = get_arm64_ftr_reg(SYS_ID_AA64ISAR1_EL1);

		if (regp)

			regp->user_mask &= ~ID_AA64ISAR1_EL1_BF16_MASK;

	}

}



static void elf_hwcap_fixup(void)

{

#ifdef CONFIG_ARM64_ERRATUM_1742098
@@ -3357,6 +3368,8 @@ void __init setup_system_features(void) 


void __init setup_user_features(void)

{

	user_feature_fixup();



	setup_elf_hwcaps(arm64_elf_hwcaps);



	if (system_supports_32bit_el0()) {