linux-kernel - Re: [PATCH 6/7] acpi, apei, ghes: Make unmapping functionality independent from architecture.

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Message-ID: <20140513201118.GF8760@pd.tnic>
Date:	Tue, 13 May 2014 22:11:18 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Tomasz Nowicki <tomasz.nowicki@...aro.org>
Cc:	rjw@...ysocki.net, lenb@...nel.org, tony.luck@...el.com,
	bp@...e.de, m.chehab@...sung.com, linux-edac@...r.kernel.org,
	x86@...nel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org
Subject: Re: [PATCH 6/7] acpi, apei, ghes: Make unmapping functionality
 independent from architecture.

On Wed, Apr 09, 2014 at 05:14:34PM +0200, Tomasz Nowicki wrote:
> Till now __flush_tlb_one was used for unmapping virtual memory which
> is x86 specific function. Replace it with more generic
> flush_tlb_kernel_range.
> 
> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@...aro.org>
> ---
>  drivers/acpi/apei/ghes.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index aaf8db3..624878b 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -185,7 +185,7 @@ static void ghes_iounmap_nmi(void __iomem *vaddr_ptr)
>  
>  	BUG_ON(vaddr != (unsigned long)GHES_IOREMAP_NMI_PAGE(base));
>  	unmap_kernel_range_noflush(vaddr, PAGE_SIZE);
> -	__flush_tlb_one(vaddr);
> +	flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
>  }
>  
>  static void ghes_iounmap_irq(void __iomem *vaddr_ptr)
> @@ -195,7 +195,7 @@ static void ghes_iounmap_irq(void __iomem *vaddr_ptr)
>  
>  	BUG_ON(vaddr != (unsigned long)GHES_IOREMAP_IRQ_PAGE(base));
>  	unmap_kernel_range_noflush(vaddr, PAGE_SIZE);
> -	__flush_tlb_one(vaddr);
> +	flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);

flush_tlb_kernel_range() does send an IPI to every core on x86 which is
much more expensive than what __flush_tlb_one does.

Fairer it would be if you added a __flush_tlb_one() version for arm
which does flush_tlb_kernel_range for you.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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