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

[Tomasz Nowicki]

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@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?
> >
> > 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
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