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

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Message-ID: <5373625B.4050401@linaro.org>
Date:	Wed, 14 May 2014 14:32:27 +0200
From:	Tomasz Nowicki <tomasz.nowicki@...aro.org>
To:	Borislav Petkov <bp@...en8.de>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Will Deacon <will.deacon@....com>
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 13.05.2014 22:11, Borislav Petkov wrote:
> 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.
>

Thanks for comment. I am not sure if maintainers will allow me to add 
sth like __flush_tlb_one() for arm/arm64. Let me ask them directly. 
Catalin, Russell what do you think?

Regards,
Tomasz
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