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

[Will Deacon]

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@xxxxxxxxxx>
> >> ---
> >>   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?

Will
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