[PATCH v5 15/22] arm64: capabilities: Change scope of VHE to Boot CPU feature

[Suzuki K Poulose]

We expect all CPUs to be running at the same EL inside the kernel
with or without VHE enabled and we have strict checks to ensure
that any mismatch triggers a kernel panic. If VHE is enabled,
we use the feature based on the boot CPU and all other CPUs
should follow. This makes it a perfect candidate for a capability
based on the boot CPU,  which should be matched by all the CPUs
(both when is ON and OFF). This saves us some not-so-pretty
hooks and special code, just for verifying the conflict.

The patch also makes the VHE capability entry depend on
CONFIG_ARM64_VHE.

Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Reviewed-by: Dave Martin <dave.martin@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
Changes since V4:
 - Fixed typo in the commit description pointed out by Dave
 - Added Dave's Reviewed-by
---
 arch/arm64/include/asm/cpufeature.h |  6 ++++++
 arch/arm64/include/asm/virt.h       |  6 ------
 arch/arm64/kernel/cpufeature.c      |  5 +++--
 arch/arm64/kernel/smp.c             | 38 -------------------------------------
 4 files changed, 9 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 2f5edef..6a12804 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -287,6 +287,12 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
 	(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;
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index c5f8944..9d1e24e 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -102,12 +102,6 @@ static inline bool has_vhe(void)
 	return false;
 }
 
-#ifdef CONFIG_ARM64_VHE
-extern void verify_cpu_run_el(void);
-#else
-static inline void verify_cpu_run_el(void) {}
-#endif
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* ! __ASM__VIRT_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b2903d5..17132a1 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1033,13 +1033,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = cpufeature_pan_not_uao,
 	},
 #endif /* CONFIG_ARM64_PAN */
+#ifdef CONFIG_ARM64_VHE
 	{
 		.desc = "Virtualization Host Extensions",
 		.capability = ARM64_HAS_VIRT_HOST_EXTN,
-		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
 		.matches = runs_at_el2,
 		.cpu_enable = cpu_copy_el2regs,
 	},
+#endif	/* CONFIG_ARM64_VHE */
 	{
 		.desc = "32-bit EL0 Support",
 		.capability = ARM64_HAS_32BIT_EL0,
@@ -1409,7 +1411,6 @@ static bool verify_local_cpu_caps(u16 scope_mask)
  */
 static void check_early_cpu_features(void)
 {
-	verify_cpu_run_el();
 	verify_cpu_asid_bits();
 	/*
 	 * Early features are used by the kernel already. If there
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 5cef114..f3e2e3a 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -85,43 +85,6 @@ enum ipi_msg_type {
 	IPI_WAKEUP
 };
 
-#ifdef CONFIG_ARM64_VHE
-
-/* Whether the boot CPU is running in HYP mode or not*/
-static bool boot_cpu_hyp_mode;
-
-static inline void save_boot_cpu_run_el(void)
-{
-	boot_cpu_hyp_mode = is_kernel_in_hyp_mode();
-}
-
-static inline bool is_boot_cpu_in_hyp_mode(void)
-{
-	return boot_cpu_hyp_mode;
-}
-
-/*
- * Verify that a secondary CPU is running the kernel at the same
- * EL as that of the boot CPU.
- */
-void verify_cpu_run_el(void)
-{
-	bool in_el2 = is_kernel_in_hyp_mode();
-	bool boot_cpu_el2 = is_boot_cpu_in_hyp_mode();
-
-	if (in_el2 ^ boot_cpu_el2) {
-		pr_crit("CPU%d: mismatched Exception Level(EL%d) with boot CPU(EL%d)\n",
-					smp_processor_id(),
-					in_el2 ? 2 : 1,
-					boot_cpu_el2 ? 2 : 1);
-		cpu_panic_kernel();
-	}
-}
-
-#else
-static inline void save_boot_cpu_run_el(void) {}
-#endif
-
 #ifdef CONFIG_HOTPLUG_CPU
 static int op_cpu_kill(unsigned int cpu);
 #else
@@ -447,7 +410,6 @@ void __init smp_prepare_boot_cpu(void)
 	 */
 	jump_label_init();
 	cpuinfo_store_boot_cpu();
-	save_boot_cpu_run_el();
 }
 
 static u64 __init of_get_cpu_mpidr(struct device_node *dn)
-- 
2.7.4