arm64: capabilities: Add support for features enabled early

The kernel detects and uses some of the features based on the boot
CPU and expects that all the following CPUs conform to it. e.g,
with VHE and the boot CPU running at EL2, the kernel decides to
keep the kernel running at EL2. If another CPU is brought up without
this capability, we use custom hooks (via check_early_cpu_features())
to handle it. To handle such capabilities add support for detecting
and enabling capabilities based on the boot CPU.

A bit is added to indicate if the capability should be detected
early on the boot CPU. The infrastructure then ensures that such
capabilities are probed and "enabled" early on in the boot CPU
and, enabled on the subsequent CPUs.

Cc: Julien Thierry <julien.thierry@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 39 insertions, 9 deletions

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 4f050259dff3..2f5edefdff99 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -108,7 +108,7 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
  *    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
@@ -121,6 +121,11 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
  *        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.
@@ -140,6 +145,11 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
  *    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
@@ -148,12 +158,21 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
  *	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
@@ -202,15 +221,26 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
  */
 
 
-/* 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
 
 /*