[PATCH v2 2/2] arm64: cpufeature: Pretend that Apple A10 family does not support 32-bit EL0
From: Nick Chan <hidden>
Date: 2024-09-09 09:15:06
Also in:
asahi, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
The Apple A10 family consists of physical performance and efficiency cores, and only one of them can be active at a given time depending on the current p-state. However, only the performance cores can execute 32-bit EL0. This results in logical cores that can only execute 32-bit EL0 in high p-states. Trying to support 32-bit EL0 on a CPU that can only execute it in certain states is a bad idea. The A10 family only supports 16KB page size anyway so many AArch32 executables won't run anyways. Pretend that it does not support 32-bit EL0 at all. Signed-off-by: Nick Chan <redacted> --- arch/arm64/kernel/cpufeature.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 718728a85430..386698f42172 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c@@ -3529,6 +3529,31 @@ void __init setup_boot_cpu_features(void) setup_boot_cpu_capabilities(); } +static void __init bad_aarch32_el0_fixup(void) +{ + static const struct midr_range bad_aarch32_el0[] = { + MIDR_ALL_VERSIONS(MIDR_APPLE_A10_T2_HURRICANE_ZEPHYR), + MIDR_ALL_VERSIONS(MIDR_APPLE_A10X_HURRICANE_ZEPHYR), + {} + }; + + /* + * The Apple A10 family can only execute 32-bit EL0 when in high + * p-states. Pretend it does not support 32-bit EL0. + */ + if (is_midr_in_range_list(read_cpuid_id(), bad_aarch32_el0)) { + struct arm64_ftr_reg *regp; + + regp = get_arm64_ftr_reg(SYS_ID_AA64PFR0_EL1); + if (!regp) + return; + u64 val = (regp->sys_val & ~ID_AA64PFR0_EL1_EL0_MASK) + | ID_AA64PFR0_EL1_EL0_IMP; + + update_cpu_ftr_reg(regp, val); + } +} + static void __init setup_system_capabilities(void) { /*
@@ -3562,6 +3587,8 @@ static void __init setup_system_capabilities(void) void __init setup_system_features(void) { + bad_aarch32_el0_fixup(); + setup_system_capabilities(); kpti_install_ng_mappings();
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2.46.0