Re: [kvm-unit-tests RFC PATCH 09/16] lib: arm/arm64: Invalidate TLB before enabling MMU

[Andrew Jones <drjones@redhat.com>]

On Wed, Aug 28, 2019 at 02:38:24PM +0100, Alexandru Elisei wrote:
> Let's invalidate the TLB before enabling the MMU, not after, so we don't
> accidently use a stale TLB mapping. For arm64, we already do that in
> asm_mmu_enable, and we issue an extra invalidation after the function
> returns. Invalidate the TLB in asm_mmu_enable for arm also, and remove the
> redundant call to tlb_flush_all.
> 
> 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 161f7a8e607c..66a05d789386 100644
> --- a/lib/arm/mmu.c
> +++ b/lib/arm/mmu.c
> @@ -57,7 +57,6 @@ 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 5d4fe4b1570b..316672545551 100644
> --- a/arm/cstart.S
> +++ b/arm/cstart.S
> @@ -160,6 +160,10 @@ halt:
>  .equ	NMRR,	0xff000004		@ MAIR1 (from Linux kernel)
>  .globl asm_mmu_enable
>  asm_mmu_enable:
> +	/* TLBIALL */
> +	mcr	p15, 0, r2, c8, c7, 0
> +	dsb	ish
> +
>  	/* TTBCR */
>  	mrc	p15, 0, r2, c2, c0, 2
>  	orr	r2, #(1 << 31)		@ TTB_EAE
> -- 
> 2.7.4
>

Reviewed-by: Andrew Jones <drjones@redhat.com>
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