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

Tomasz Nowicki
2014-05-14T12:52:01Z

On 14.05.2014 14:48, Will Deacon wrote:
> On Wed, May 14, 2014 at 01:45:07PM +0100, Catalin Marinas wrote:
>> On Wed, May 14, 2014 at 01:35:42PM +0100, Will Deacon wrote:
>>> On Wed, May 14, 2014 at 01:32:27PM +0100, Tomasz Nowicki wrote:
>>>> 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@linaro.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?
>>>
>>> I don't have the background for this, but if you don't need broadcasting
>>> (if this avoids IPIs on x86, I guess you don't) then why not use
>>> local_flush_tlb_kernel_range instead?
>>
>> Is this generic enough (we don't have it on arm64)?
>
> Well, it's more popular than __flush_tlb_one and the naming is more
> descriptive imo.

I am aiming ARM64 but ideally it should work for x86, arm64 and arm.

Tomasz