arm64: unify idmap removal

We currently open-code the removal of the idmap and restoration of the
current task's MMU state in a few places.

Before introducing yet more copies of this sequence, unify these to call
a new helper, cpu_uninstall_idmap.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 600eacb9f7d5..b1b2514d8883 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -27,6 +27,7 @@
 #include <asm-generic/mm_hooks.h>
 #include <asm/cputype.h>
 #include <asm/pgtable.h>
+#include <asm/tlbflush.h>
 
 #ifdef CONFIG_PID_IN_CONTEXTIDR
 static inline void contextidr_thread_switch(struct task_struct *next)
@@ -90,6 +91,30 @@ static inline void cpu_set_default_tcr_t0sz(void)
 }
 
 /*
+ * Remove the idmap from TTBR0_EL1 and install the pgd of the active mm.
+ *
+ * The idmap lives in the same VA range as userspace, but uses global entries
+ * and may use a different TCR_EL1.T0SZ. To avoid issues resulting from
+ * speculative TLB fetches, we must temporarily install the reserved page
+ * tables while we invalidate the TLBs and set up the correct TCR_EL1.T0SZ.
+ *
+ * If current is a not a user task, the mm covers the TTBR1_EL1 page tables,
+ * which should not be installed in TTBR0_EL1. In this case we can leave the
+ * reserved page tables in place.
+ */
+static inline void cpu_uninstall_idmap(void)
+{
+	struct mm_struct *mm = current->active_mm;
+
+	cpu_set_reserved_ttbr0();
+	local_flush_tlb_all();
+	cpu_set_default_tcr_t0sz();
+
+	if (mm != &init_mm)
+		cpu_switch_mm(mm->pgd, mm);
+}
+
+/*
  * It would be nice to return ASIDs back to the allocator, but unfortunately
  * that introduces a race with a generation rollover where we could erroneously
  * free an ASID allocated in a future generation. We could workaround this by