Re: [PATCH V3 4/4] acpi, apei: use EFI memmap to map GHES memory

[Zhang, Jonathan Zhixiong]

On 6/12/2015 9:29 AM, Borislav Petkov wrote:
> On Thu, Jun 11, 2015 at 11:26:00AM -0700, 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. When firmware
> > updated GHES memory region with uncached access attribute, Linux
> > reads stale data from cache.
> >
> > GHES memory region should be mapped with cache attributes
> > according to EFI memory map when applicable. On such system, if
> > firmware updates RAM directly without going through cache,
> > EFI memory map has GHES memory region defined as uncached;
> > If firmware updates cache, EFI memory map has GHES memory region
> > defined as cached.
> >
> > On EFI system, if GHES memory region has EFI_MEMORY_UC attribute
> > defined, map the page with arch defined UC page protection type.
> >
> > Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
> > ---
> >   drivers/acpi/apei/ghes.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> > index e82d0976a5d0..5cfd951ebf67 100644
> > --- a/drivers/acpi/apei/ghes.c
> > +++ b/drivers/acpi/apei/ghes.c
> > @@ -48,6 +48,7 @@
> >   #include <linux/pci.h>
> >   #include <linux/aer.h>
> >   #include <linux/nmi.h>
> > +#include <linux/efi.h>
> >
> >   #include <acpi/ghes.h>
> >   #include <acpi/apei.h>
> > @@ -164,8 +165,14 @@ 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,
> > +
> > +	if (efi_mem_attributes(pfn << PAGE_SHIFT) & EFI_MEMORY_UC) {
> > +		ioremap_page_range(vaddr, vaddr + PAGE_SIZE,
> > +				   pfn << PAGE_SHIFT, ARCH_APEI_PAGE_KERNEL_UC);
> > +	} else {
> > +		ioremap_page_range(vaddr, vaddr + PAGE_SIZE,
> >   			   pfn << PAGE_SHIFT, PAGE_KERNEL);
> > +	}
> >
> >   	return (void __iomem *)vaddr;
>
> This is still hacky. All of a sudden, ghes code gets to know about EFI
> which looks like a mishmash to me.
>
> Maybe it would be cleaner if you added an arch-specific
>
> 	arch_get_mem_attribute(phys_addr);
>
> which returns a pgprot_t thing which you can use directly above, like
> so:
>
>          ioremap_page_range(vaddr,
> 			   vaddr + PAGE_SIZE,
>                             pfn << PAGE_SHIFT,
> 			   arch_get_mem_attribute(pfn << PAGE_SHIFT));
>
> Each arch can then return what it likes with arch_get_mem_attribute().
>
Thanks for the review, Borislav. I will do that. Since such function
is only needed for APEI functionality, at least as of today, I will
name it arch_apei_get_mem_attribute().
I will add implementations for arm64 and x86 since those are the only
archs having HAVE_ACPI_APEI defined in Kconfig. The upstream kernel
today does not have HAVE_ACPI_APEI defined for arm64, but it needs to
be and will be.

--
Jonathan (Zhixiong) Zhang
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/