[PATCH 3/5] arm64: Workaround Cortex-A77 erratum 1542418 on boot due to kexec

[Suzuki K Poulose]

From: James Morse <james.morse@xxxxxxx>

Kexec allows us to inherit dirty ASIDs from a previous kernel. We can't
wait until the next ASID rollover to cleanup, do it early as part of
the cpu-errata's enable callback.

This extends __arm64_workaround_1542418_asid_rollover() to put everything
back as it was.

Signed-off-by: James Morse <james.morse@xxxxxxx>
[ skip CPUs not affected, refactor cpu_enable callback ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
 arch/arm64/include/asm/mmu_context.h |  1 +
 arch/arm64/kernel/cpu_errata.c       | 14 ++++++++++++++
 arch/arm64/mm/context.c              | 17 +++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 3827ff4040a3..434a5c661d78 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -247,6 +247,7 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
 
 void verify_cpu_asid_bits(void);
 void post_ttbr_update_workaround(void);
+void arm64_workaround_1542418_asid_rollover(void);
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index a66d433d0113..4656157ffa36 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -12,6 +12,7 @@
 #include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/cpufeature.h>
+#include <asm/mmu_context.h>
 #include <asm/smp_plat.h>
 
 static bool __maybe_unused
@@ -650,6 +651,18 @@ needs_tx2_tvm_workaround(const struct arm64_cpu_capabilities *entry,
 	return false;
 }
 
+#ifdef CONFIG_ARM64_ERRATUM_1542418
+static void run_workaround_1542418_asid_rollover(const struct arm64_cpu_capabilities *c)
+{
+	/*
+	 * If this CPU is affected by the erratum, run the workaround
+	 * to protect us in case we are running on a kexec'ed kernel.
+	 */
+	if (c->matches(c, SCOPE_LOCAL_CPU))
+		arm64_workaround_1542418_asid_rollover();
+}
+#endif
+
 #ifdef CONFIG_HARDEN_EL2_VECTORS
 
 static const struct midr_range arm64_harden_el2_vectors[] = {
@@ -932,6 +945,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		.desc = "ARM erratum 1542418",
 		.capability = ARM64_WORKAROUND_1542418,
 		ERRATA_MIDR_RANGE(MIDR_CORTEX_A77, 0, 0, 1, 0),
+		.cpu_enable = run_workaround_1542418_asid_rollover,
 	},
 #endif
 	{
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index ae3ee8e101d6..ad4e78bb68ed 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -129,6 +129,23 @@ static void __arm64_workaround_1542418_asid_rollover(void)
 	 */
 }
 
+void arm64_workaround_1542418_asid_rollover(void)
+{
+	u64 ttbr0 = read_sysreg(ttbr0_el1);
+
+	lockdep_assert_irqs_disabled();
+
+	/* Mirror check_and_switch_context() */
+	if (system_supports_cnp())
+		cpu_set_reserved_ttbr0();
+
+	__arm64_workaround_1542418_asid_rollover();
+	isb();
+
+	write_sysreg(ttbr0, ttbr0_el1);
+	isb();
+}
+
 static void flush_context(void)
 {
 	int i;
-- 
2.23.0