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Diffstat (limited to 'arch/arm64/include/asm/cpufeature.h')
-rw-r--r--arch/arm64/include/asm/cpufeature.h262
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);