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

Will Deacon
2014-05-14T12:48:39Z

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.

Will