linux-kernel - Re: [PATCH V7 4/5] arm64: apei: implement arch_apei_get_mem

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Date:	Fri, 24 Jul 2015 15:57:08 +0100
From:	Will Deacon <will.deacon@....com>
To:	"Jonathan (Zhixiong) Zhang" <zjzhang@...eaurora.org>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"fu.wei@...aro.org" <fu.wei@...aro.org>,
	"al.stone@...aro.org" <al.stone@...aro.org>,
	"bp @ alien8 . de Matt Fleming" <matt.fleming@...el.com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [PATCH V7 4/5] arm64: apei: implement
 arch_apei_get_mem_attributes()

On Tue, Jul 21, 2015 at 10:59:19PM +0100, Jonathan (Zhixiong) Zhang wrote:
> From: "Jonathan (Zhixiong) Zhang" <zjzhang@...eaurora.org>
> 
> If the physical address has memory attributes defined by EFI
> memmap as EFI_MEMORY_UC, the page protection type is
> PROT_DEVICE_nGnRE. Otherwise, the page protection type is
> PAGE_KERNEL.
> 
> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@...eaurora.org>
> ---
> This patch applies cleanly to efi-next-14364 of efi/next and
> arm64-upstream-13521 of arm64/master, but needed slight change
> to apply to next-20150720 of linux-next/master and
> pm+acpi-4.2-rc3 of linux-pm/master. The later two branches
> has newer arch/arm64/include/asm/acpi.h with following patch:
>   b6cfb277378e ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro
> ---
>  arch/arm64/include/asm/acpi.h | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)

[...]

> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> +static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
> +{
> +	pgprot_t prot;
> +
> +	prot = efi_mem_attributes(addr);
> +	if (prot & EFI_MEMORY_UC)
> +		return PROT_DEVICE_nGnRnE;
> +	if (prot & EFI_MEMORY_WC)
> +		return PROT_NORMAL_NC;

Can we not use pgprot_noncached and pgprot_writecombine for these two?

> +	if (prot & EFI_MEMORY_WT)
> +		return PROT_NORMAL_WT;

Then you could add pgprot_writethrough for this guy.

Will
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