Re: [PATCH 2/2] acpi, apei: use appropriate pgprot_t to map GHES memory

[Zhang, Jonathan Zhixiong]

On 8/17/2015 6:13 AM, Matt Fleming wrote:
> On Fri, 14 Aug, at 03:37:30PM, Jonathan (Zhixiong) Zhang wrote:
> > From: "Jonathan (Zhixiong) Zhang" <zjzhang@xxxxxxxxxxxxxx>
> >
> > With ACPI APEI firmware first handling, generic hardware error
> > record is updated by firmware in GHES memory region. On an arm64
> > platform, firmware updates GHES memory region with uncached
> > access attribute, and then Linux reads stale data from cache.
> >
> > With current code, GHES memory region is mapped with PAGE_KERNEL
> > based on the assumption that cache coherency of GHES memory region
> > is maintained by firmware on all platforms. This assumption is
> > not true for above mentioned arm64 platform.
> >
> > Instead GHES memory region should be mapped with page protection type
> > according to what is returned from arch_apei_get_mem_attribute().
> >
> > Acked-by: Borislav Petkov <bp@xxxxxxx>
> > Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
> > ---
> >   drivers/acpi/apei/ghes.c | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> > index 23981ac1c6c2..f742335bd8bb 100644
> > --- a/drivers/acpi/apei/ghes.c
> > +++ b/drivers/acpi/apei/ghes.c
> > @@ -160,8 +160,10 @@ static void __iomem *ghes_ioremap_pfn_irq(u64 pfn)
> >   	unsigned long vaddr;
> >
> >   	vaddr = (unsigned long)GHES_IOREMAP_IRQ_PAGE(ghes_ioremap_area->addr);
> > -	ioremap_page_range(vaddr, vaddr + PAGE_SIZE,
> > -			   pfn << PAGE_SHIFT, PAGE_KERNEL);
> > +	ioremap_page_range(vaddr,
> > +			   vaddr + PAGE_SIZE,
> > +			   pfn << PAGE_SHIFT,
> > +			   arch_apei_get_mem_attribute(pfn << PAGE_SHIFT));
> >
> >   	return (void __iomem *)vaddr;
> >   }
>
> Y'know, this would be more readable if written as,
>
> 	unsigned long vaddr, paddr;
> 	pgprot_t prot;
>
>    	vaddr = (unsigned long)GHES_IOREMAP_IRQ_PAGE(ghes_ioremap_area->addr);
>
> 	paddr = pfn << PAGE_SHIFT;
> 	prot = arch_apei_get_mem_attribute(paddr);
>
> 	ioremap_page_range(vaddr, vaddr + PAGE_SIZE, paddr, prot);
>
> But either way,
>
> Reviewed-by: Matt Fleming <matt.fleming@xxxxxxxxx>
Thanks. I will go with the easier to read way.
>

--
Jonathan (Zhixiong) Zhang
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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