@@ -104,7 +104,7 @@ extern struct arm64_ftr_reg arm64_ftr_re
* 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 two cases:
+ * 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
@@ -117,6 +117,11 @@ extern struct arm64_ftr_reg arm64_ftr_re
* 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.
@@ -136,6 +141,11 @@ extern struct arm64_ftr_reg arm64_ftr_re
* 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
@@ -144,12 +154,21 @@ extern struct arm64_ftr_reg arm64_ftr_re
* secondary_start_kernel()-> check_local_cpu_capabilities()
*
* As explained in (2) above, capabilities could be finalised at
- * different points in the execution. Each CPU is verified against the
- * "finalised" capabilities and 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.
+ * 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
@@ -198,15 +217,26 @@ extern struct arm64_ftr_reg arm64_ftr_re
*/
-/* Decide how the capability is detected. On a local CPU vs System wide */
+/*
+ * 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_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
/*
@@ -485,7 +485,7 @@ static void __init init_cpu_ftr_reg(u32
}
extern const struct arm64_cpu_capabilities arm64_errata[];
-static void update_cpu_capabilities(u16 scope_mask);
+static void __init setup_boot_cpu_capabilities(void);
void __init init_cpu_features(struct cpuinfo_arm64 *info)
{
@@ -525,10 +525,10 @@ void __init init_cpu_features(struct cpu
}
/*
- * Run the errata work around and local feature checks on the
- * boot CPU, once we have initialised the cpu feature infrastructure.
+ * Detect and enable early CPU capabilities based on the boot CPU,
+ * after we have initialised the CPU feature infrastructure.
*/
- update_cpu_capabilities(SCOPE_LOCAL_CPU);
+ setup_boot_cpu_capabilities();
}
static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new)
@@ -1219,13 +1219,24 @@ __enable_cpu_capabilities(const struct a
if (caps->cpu_enable) {
/*
- * Use stop_machine() as it schedules the work allowing
- * us to modify PSTATE, instead of on_each_cpu() which
- * uses an IPI, giving us a PSTATE that disappears when
- * we return.
+ * Capabilities with SCOPE_BOOT_CPU scope are finalised
+ * before any secondary CPU boots. Thus, each secondary
+ * will enable the capability as appropriate via
+ * check_local_cpu_capabilities(). The only exception is
+ * the boot CPU, for which the capability must be
+ * enabled here. This approach avoids costly
+ * stop_machine() calls for this case.
+ *
+ * Otherwise, use stop_machine() as it schedules the
+ * work allowing us to modify PSTATE, instead of
+ * on_each_cpu() which uses an IPI, giving us a PSTATE
+ * that disappears when we return.
*/
- stop_machine(__enable_cpu_capability, (void *)caps,
- cpu_online_mask);
+ if (scope_mask & SCOPE_BOOT_CPU)
+ caps->cpu_enable(caps);
+ else
+ stop_machine(__enable_cpu_capability,
+ (void *)caps, cpu_online_mask);
}
}
}
@@ -1323,6 +1334,12 @@ static void check_early_cpu_features(voi
{
verify_cpu_run_el();
verify_cpu_asid_bits();
+ /*
+ * Early features are used by the kernel already. If there
+ * is a conflict, we cannot proceed further.
+ */
+ if (!verify_local_cpu_caps(SCOPE_BOOT_CPU))
+ cpu_panic_kernel();
}
static void
@@ -1348,7 +1365,12 @@ verify_local_elf_hwcaps(const struct arm
*/
static void verify_local_cpu_capabilities(void)
{
- if (!verify_local_cpu_caps(SCOPE_ALL))
+ /*
+ * The capabilities with SCOPE_BOOT_CPU are checked from
+ * check_early_cpu_features(), as they need to be verified
+ * on all secondary CPUs.
+ */
+ if (!verify_local_cpu_caps(SCOPE_ALL & ~SCOPE_BOOT_CPU))
cpu_die_early();
verify_local_elf_hwcaps(arm64_elf_hwcaps);
@@ -1376,6 +1398,14 @@ void check_local_cpu_capabilities(void)
verify_local_cpu_capabilities();
}
+static void __init setup_boot_cpu_capabilities(void)
+{
+ /* Detect capabilities with either SCOPE_BOOT_CPU or SCOPE_LOCAL_CPU */
+ update_cpu_capabilities(SCOPE_BOOT_CPU | SCOPE_LOCAL_CPU);
+ /* Enable the SCOPE_BOOT_CPU capabilities alone right away */
+ enable_cpu_capabilities(SCOPE_BOOT_CPU);
+}
+
DEFINE_STATIC_KEY_FALSE(arm64_const_caps_ready);
EXPORT_SYMBOL(arm64_const_caps_ready);
@@ -1397,10 +1427,11 @@ static void __init setup_system_capabili
/*
* We have finalised the system-wide safe feature
* registers, finalise the capabilities that depend
- * on it. Also enable all the available capabilities.
+ * on it. Also enable all the available capabilities,
+ * that are not enabled already.
*/
update_cpu_capabilities(SCOPE_SYSTEM);
- enable_cpu_capabilities(SCOPE_ALL);
+ enable_cpu_capabilities(SCOPE_ALL & ~SCOPE_BOOT_CPU);
}
void __init setup_cpu_features(void)