[PATCH 1/2][Bionic] Revert "arm64: capabilities: Change scope of VHE to Boot CPU feature"

[Ike Panhc]

BugLink: http://bugs.launchpad.net/bugs/1852723

The 4.15.0-71.80 generic kernel can not boot on several arm64 machines.
Bisect patches and find out we can solve this problem by reverting
a single patch which comes from stable kernel update.

This reverts commit 628859e8621cbb105cfbfa2138a68ddbd72958a7.

Signed-off-by: Ike Panhc <ike.pan at canonical.com>
---
 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, 46 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index f3aa281b97cb..513570cd3e6f 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -289,12 +289,6 @@ 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 9d1e24e030b3..c5f89442785c 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -102,6 +102,12 @@ 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 d19a7b8bb6fb..672443860341 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1113,15 +1113,13 @@ 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_STRICT_BOOT_CPU_FEATURE,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
 		.matches = runs_at_el2,
 		.cpu_enable = cpu_copy_el2regs,
 	},
-#endif	/* CONFIG_ARM64_VHE */
 	{
 		.desc = "32-bit EL0 Support",
 		.capability = ARM64_HAS_32BIT_EL0,
@@ -1491,6 +1489,7 @@ 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 2faa9863d2e5..a077c3d2fd73 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -85,6 +85,43 @@ 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
@@ -410,6 +447,7 @@ 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)
-- 
2.17.1