diff options
Diffstat (limited to 'arch/arm64/include/asm/cpufeature.h')
| -rw-r--r-- | arch/arm64/include/asm/cpufeature.h | 262 |
1 files changed, 246 insertions, 16 deletions
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 060e3a4008ab..09b0f2a80c8f 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -10,6 +10,7 @@ #define __ASM_CPUFEATURE_H #include <asm/cpucaps.h> +#include <asm/cputype.h> #include <asm/fpsimd.h> #include <asm/hwcap.h> #include <asm/sigcontext.h> @@ -89,24 +90,231 @@ struct arm64_ftr_reg { extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; -/* scope of capability check */ -enum { - SCOPE_SYSTEM, - SCOPE_LOCAL_CPU, -}; +/* + * CPU capabilities: + * + * We use arm64_cpu_capabilities to represent system features, errata work + * arounds (both used internally by kernel and tracked in cpu_hwcaps) and + * ELF HWCAPs (which are exposed to user). + * + * To support systems with heterogeneous CPUs, we need to make sure that we + * detect the capabilities correctly on the system and take appropriate + * measures to ensure there are no incompatibilities. + * + * This comment tries to explain how we treat the capabilities. + * Each capability has the following list of attributes : + * + * 1) Scope of Detection : The system detects a given capability by + * performing some checks at runtime. This could be, e.g, checking the + * value of a field in CPU ID feature register or checking the cpu + * model. The capability provides a call back ( @matches() ) to + * perform the check. Scope defines how the checks should be performed. + * There are three cases: + * + * a) SCOPE_LOCAL_CPU: check all the CPUs and "detect" if at least one + * matches. This implies, we have to run the check on all the + * booting CPUs, until the system decides that state of the + * capability is finalised. (See section 2 below) + * Or + * b) SCOPE_SYSTEM: check all the CPUs and "detect" if all the CPUs + * matches. This implies, we run the check only once, when the + * system decides to finalise the state of the capability. If the + * capability relies on a field in one of the CPU ID feature + * registers, we use the sanitised value of the register from the + * CPU feature infrastructure to make the decision. + * Or + * c) SCOPE_BOOT_CPU: Check only on the primary boot CPU to detect the + * feature. This category is for features that are "finalised" + * (or used) by the kernel very early even before the SMP cpus + * are brought up. + * + * The process of detection is usually denoted by "update" capability + * state in the code. + * + * 2) Finalise the state : The kernel should finalise the state of a + * capability at some point during its execution and take necessary + * actions if any. Usually, this is done, after all the boot-time + * enabled CPUs are brought up by the kernel, so that it can make + * better decision based on the available set of CPUs. However, there + * are some special cases, where the action is taken during the early + * boot by the primary boot CPU. (e.g, running the kernel at EL2 with + * Virtualisation Host Extensions). The kernel usually disallows any + * changes to the state of a capability once it finalises the capability + * and takes any action, as it may be impossible to execute the actions + * safely. A CPU brought up after a capability is "finalised" is + * referred to as "Late CPU" w.r.t the capability. e.g, all secondary + * CPUs are treated "late CPUs" for capabilities determined by the boot + * CPU. + * + * At the moment there are two passes of finalising the capabilities. + * a) Boot CPU scope capabilities - Finalised by primary boot CPU via + * setup_boot_cpu_capabilities(). + * b) Everything except (a) - Run via setup_system_capabilities(). + * + * 3) Verification: When a CPU is brought online (e.g, by user or by the + * kernel), the kernel should make sure that it is safe to use the CPU, + * by verifying that the CPU is compliant with the state of the + * capabilities finalised already. This happens via : + * + * secondary_start_kernel()-> check_local_cpu_capabilities() + * + * As explained in (2) above, capabilities could be finalised at + * different points in the execution. Each newly booted CPU is verified + * against the capabilities that have been finalised by the time it + * boots. + * + * a) SCOPE_BOOT_CPU : All CPUs are verified against the capability + * except for the primary boot CPU. + * + * b) SCOPE_LOCAL_CPU, SCOPE_SYSTEM: All CPUs hotplugged on by the + * user after the kernel boot are verified against the capability. + * + * If there is a conflict, the kernel takes an action, based on the + * severity (e.g, a CPU could be prevented from booting or cause a + * kernel panic). The CPU is allowed to "affect" the state of the + * capability, if it has not been finalised already. See section 5 + * for more details on conflicts. + * + * 4) Action: As mentioned in (2), the kernel can take an action for each + * detected capability, on all CPUs on the system. Appropriate actions + * include, turning on an architectural feature, modifying the control + * registers (e.g, SCTLR, TCR etc.) or patching the kernel via + * alternatives. The kernel patching is batched and performed at later + * point. The actions are always initiated only after the capability + * is finalised. This is usally denoted by "enabling" the capability. + * The actions are initiated as follows : + * a) Action is triggered on all online CPUs, after the capability is + * finalised, invoked within the stop_machine() context from + * enable_cpu_capabilitie(). + * + * b) Any late CPU, brought up after (1), the action is triggered via: + * + * check_local_cpu_capabilities() -> verify_local_cpu_capabilities() + * + * 5) Conflicts: Based on the state of the capability on a late CPU vs. + * the system state, we could have the following combinations : + * + * x-----------------------------x + * | Type | System | Late CPU | + * |-----------------------------| + * | a | y | n | + * |-----------------------------| + * | b | n | y | + * x-----------------------------x + * + * Two separate flag bits are defined to indicate whether each kind of + * conflict can be allowed: + * ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU - Case(a) is allowed + * ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU - Case(b) is allowed + * + * Case (a) is not permitted for a capability that the system requires + * all CPUs to have in order for the capability to be enabled. This is + * typical for capabilities that represent enhanced functionality. + * + * Case (b) is not permitted for a capability that must be enabled + * during boot if any CPU in the system requires it in order to run + * safely. This is typical for erratum work arounds that cannot be + * enabled after the corresponding capability is finalised. + * + * In some non-typical cases either both (a) and (b), or neither, + * should be permitted. This can be described by including neither + * or both flags in the capability's type field. + */ + + +/* + * Decide how the capability is detected. + * On any local CPU vs System wide vs the primary boot CPU + */ +#define ARM64_CPUCAP_SCOPE_LOCAL_CPU ((u16)BIT(0)) +#define ARM64_CPUCAP_SCOPE_SYSTEM ((u16)BIT(1)) +/* + * The capabilitiy is detected on the Boot CPU and is used by kernel + * during early boot. i.e, the capability should be "detected" and + * "enabled" as early as possibly on all booting CPUs. + */ +#define ARM64_CPUCAP_SCOPE_BOOT_CPU ((u16)BIT(2)) +#define ARM64_CPUCAP_SCOPE_MASK \ + (ARM64_CPUCAP_SCOPE_SYSTEM | \ + ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ + ARM64_CPUCAP_SCOPE_BOOT_CPU) + +#define SCOPE_SYSTEM ARM64_CPUCAP_SCOPE_SYSTEM +#define SCOPE_LOCAL_CPU ARM64_CPUCAP_SCOPE_LOCAL_CPU +#define SCOPE_BOOT_CPU ARM64_CPUCAP_SCOPE_BOOT_CPU +#define SCOPE_ALL ARM64_CPUCAP_SCOPE_MASK + +/* + * Is it permitted for a late CPU to have this capability when system + * hasn't already enabled it ? + */ +#define ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU ((u16)BIT(4)) +/* Is it safe for a late CPU to miss this capability when system has it */ +#define ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU ((u16)BIT(5)) + +/* + * CPU errata workarounds that need to be enabled at boot time if one or + * more CPUs in the system requires it. When one of these capabilities + * has been enabled, it is safe to allow any CPU to boot that doesn't + * require the workaround. However, it is not safe if a "late" CPU + * requires a workaround and the system hasn't enabled it already. + */ +#define ARM64_CPUCAP_LOCAL_CPU_ERRATUM \ + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU) +/* + * CPU feature detected at boot time based on system-wide value of a + * feature. It is safe for a late CPU to have this feature even though + * the system hasn't enabled it, although the featuer will not be used + * by Linux in this case. If the system has enabled this feature already, + * then every late CPU must have it. + */ +#define ARM64_CPUCAP_SYSTEM_FEATURE \ + (ARM64_CPUCAP_SCOPE_SYSTEM | ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) +/* + * CPU feature detected at boot time based on feature of one or more CPUs. + * All possible conflicts for a late CPU are ignored. + */ +#define ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE \ + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ + ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU | \ + ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) + +/* + * CPU feature detected at boot time, on one or more CPUs. A late CPU + * is not allowed to have the capability when the system doesn't have it. + * It is Ok for a late CPU to miss the feature. + */ +#define ARM64_CPUCAP_BOOT_RESTRICTED_CPU_LOCAL_FEATURE \ + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ + ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU) + +/* + * CPU feature used early in the boot based on the boot CPU. All secondary + * CPUs must match the state of the capability as detected by the boot CPU. + */ +#define ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE ARM64_CPUCAP_SCOPE_BOOT_CPU struct arm64_cpu_capabilities { const char *desc; u16 capability; - int def_scope; /* default scope */ + u16 type; bool (*matches)(const struct arm64_cpu_capabilities *caps, int scope); - int (*enable)(void *); /* Called on all active CPUs */ + /* + * Take the appropriate actions to enable this capability for this CPU. + * For each successfully booted CPU, this method is called for each + * globally detected capability. + */ + void (*cpu_enable)(const struct arm64_cpu_capabilities *cap); union { struct { /* To be used for erratum handling only */ - u32 midr_model; - u32 midr_range_min, midr_range_max; + struct midr_range midr_range; + const struct arm64_midr_revidr { + u32 midr_rv; /* revision/variant */ + u32 revidr_mask; + } * const fixed_revs; }; + const struct midr_range *midr_range_list; struct { /* Feature register checking */ u32 sys_reg; u8 field_pos; @@ -115,9 +323,38 @@ struct arm64_cpu_capabilities { bool sign; unsigned long hwcap; }; + /* + * A list of "matches/cpu_enable" pair for the same + * "capability" of the same "type" as described by the parent. + * Only matches(), cpu_enable() and fields relevant to these + * methods are significant in the list. The cpu_enable is + * invoked only if the corresponding entry "matches()". + * However, if a cpu_enable() method is associated + * with multiple matches(), care should be taken that either + * the match criteria are mutually exclusive, or that the + * method is robust against being called multiple times. + */ + const struct arm64_cpu_capabilities *match_list; }; }; +static inline int cpucap_default_scope(const struct arm64_cpu_capabilities *cap) +{ + return cap->type & ARM64_CPUCAP_SCOPE_MASK; +} + +static inline bool +cpucap_late_cpu_optional(const struct arm64_cpu_capabilities *cap) +{ + return !!(cap->type & ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU); +} + +static inline bool +cpucap_late_cpu_permitted(const struct arm64_cpu_capabilities *cap) +{ + return !!(cap->type & ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU); +} + extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS); extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS]; extern struct static_key_false arm64_const_caps_ready; @@ -236,15 +473,8 @@ static inline bool id_aa64pfr0_sve(u64 pfr0) } void __init setup_cpu_features(void); - -void update_cpu_capabilities(const struct arm64_cpu_capabilities *caps, - const char *info); -void enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps); void check_local_cpu_capabilities(void); -void update_cpu_errata_workarounds(void); -void __init enable_errata_workarounds(void); -void verify_local_cpu_errata_workarounds(void); u64 read_sanitised_ftr_reg(u32 id); |