[kvm-unit-tests PATCH v2 17/18] arm/arm64: Invalidate TLB before enabling MMU

[Alexandru Elisei <alexandru.elisei@arm.com>]

Let's invalidate the TLB before enabling the MMU, not after, so we don't
accidently use a stale TLB mapping. For arm, we add a TLBIALL operation,
which applies only to the PE that executed the instruction [1]. For arm64,
we already do that in asm_mmu_enable.

We now find ourselves in a situation where we issue an extra invalidation
after asm_mmu_enable returns. Remove this redundant call to tlb_flush_all.

[1] ARM DDI 0406C.d, section B3.10.6

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
 lib/arm/mmu.c | 1 -
 arm/cstart.S  | 4 ++++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
index 773c764c4836..530d6b825398 100644
--- a/lib/arm/mmu.c
+++ b/lib/arm/mmu.c
@@ -59,7 +59,6 @@ void mmu_enable(pgd_t *pgtable)
 	struct thread_info *info = current_thread_info();
 
 	asm_mmu_enable(__pa(pgtable));
-	flush_tlb_all();
 
 	info->pgtable = pgtable;
 	mmu_mark_enabled(info->cpu);
diff --git a/arm/cstart.S b/arm/cstart.S
index 3c2a3bcde61a..32b2b4f03098 100644
--- a/arm/cstart.S
+++ b/arm/cstart.S
@@ -161,6 +161,10 @@ halt:
 .equ	NMRR,	0xff000004		@ MAIR1 (from Linux kernel)
 .globl asm_mmu_enable
 asm_mmu_enable:
+	/* TLBIALL */
+	mcr	p15, 0, r2, c8, c7, 0
+	dsb	nsh
+
 	/* TTBCR */
 	ldr	r2, =(TTBCR_EAE | 				\
 		      TTBCR_SH0_SHARED | 			\
-- 
2.20.1