linux-kernel - Re: [PATCH] arm64: Add flush_cache_vmap call in __early_set

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Date:	Fri, 06 Jun 2014 10:37:29 -0400
From:	Mark Salter <msalter@...hat.com>
To:	Leif Lindholm <leif.lindholm@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	catalin.marinas@....com, will.deacon@....com,
	steve.capper@...aro.org
Subject: Re: [PATCH] arm64: Add flush_cache_vmap call in __early_set_fixmap

On Fri, 2014-06-06 at 11:29 +0100, Leif Lindholm wrote:
> __early_set_fixmap does not do any synchronization when called to set a
> fixmap entry. Add call to flush_vmap_cache().
> 
> Tested on hardware.
> 
> Signed-off-by: Leif Lindholm <leif.lindholm@...aro.org>
> Tested-by: Graeme Gregory <graeme.gregory@...aro.org>
> Cc: Steve Capper <steve.capper@...aro.org>
> ---
>  arch/arm64/mm/ioremap.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
> index 7ec3283..5b8766c 100644
> --- a/arch/arm64/mm/ioremap.c
> +++ b/arch/arm64/mm/ioremap.c
> @@ -176,9 +176,10 @@ void __init __early_set_fixmap(enum fixed_addresses idx,
>  
>  	pte = early_ioremap_pte(addr);
>  
> -	if (pgprot_val(flags))
> +	if (pgprot_val(flags)) {
>  		set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
> -	else {
> +		flush_cache_vmap(addr, addr + PAGE_SIZE);
> +	} else {
>  		pte_clear(&init_mm, addr, pte);
>  		flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
>  	}

I'm confused by the commit message mentioning synchronization but
the code doing a cache flush. I see that arm64 implementation of
flush_cache_vmap() is just a dsb(). If it is synchronization that
we need here (and it certainly looks like we do), why not just add
the dsb() directly to make that clear?


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