linux-kernel - Re: [PATCH V9 2/5] x86: acpi: implement arch_apei_get_mem

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Date:	Mon, 3 Aug 2015 17:22:23 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	"Jonathan (Zhixiong) Zhang" <zjzhang@...eaurora.org>
Cc:	Matt Fleming <matt.fleming@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	ying.huang@...el.com, tony.luck@...il.com, fu.wei@...aro.org,
	al.stone@...aro.org, bp@...en8.de, rjw@...ysocki.net,
	catalin.marinas@....com, will.deacon@....com,
	hanjun.guo@...aro.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	timur@...eaurora.org
Subject: Re: [PATCH V9 2/5] x86: acpi: implement
 arch_apei_get_mem_attributes()

On Thu, 30 Jul, at 02:35:06PM, Jonathan (Zhixiong) Zhang wrote:
> From: "Jonathan (Zhixiong) Zhang" <zjzhang@...eaurora.org>
> 
> ... to allow arch specific implementation of getting page
> protection type associated with a physical address.
> 
> On x86, we currently have no way to lookup the EFI memory map
> attributes for a region in a consistent way because the
> memmap is discarded after efi_free_boot_services(). So if
> you call efi_mem_attributes() during boot and at runtime,
> you could theoretically see different attributes.
> 
> Since we are yet to see any x86 platforms that require
> anything other than PAGE_KERNEL (some arm64 platforms
> require the equivalent of PAGE_KERNEL_NOCACHE), return that
> until we know differently.
> 
> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@...eaurora.org>
> ---
>  arch/x86/kernel/acpi/apei.c | 19 +++++++++++++++++++
>  include/acpi/apei.h         |  1 +
>  2 files changed, 20 insertions(+)
> 
> diff --git a/arch/x86/kernel/acpi/apei.c b/arch/x86/kernel/acpi/apei.c
> index c280df6b2aa2..675bd46c4e17 100644
> --- a/arch/x86/kernel/acpi/apei.c
> +++ b/arch/x86/kernel/acpi/apei.c
> @@ -60,3 +60,22 @@ void arch_apei_flush_tlb_one(unsigned long addr)
>  {
>  	__flush_tlb_one(addr);
>  }
> +
> +static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
> +{
> +
> +	/*
> +	 * We currently have no way to lookup the EFI memory map
> +	 * attributes for a region in a consistent way because the
> +	 * memmap is discarded after efi_free_boot_services(). So if
> +	 * you call efi_mem_attributes() during boot and at runtime,
> +	 * you could theoretically see different attributes.
> +	 *
> +	 * Since we are yet to see any x86 platforms that require
> +	 * anything other than PAGE_KERNEL (some arm64 platforms
> +	 * require the equivalent of PAGE_KERNEL_NOCACHE), return that
> +	 * until we know differently.
> +	 */
> +
> +	return __pgprot(PAGE_KERNEL);
> +}
> diff --git a/include/acpi/apei.h b/include/acpi/apei.h
> index 284801ac7042..64a12ce9880b 100644
> --- a/include/acpi/apei.h
> +++ b/include/acpi/apei.h
> @@ -46,6 +46,7 @@ int erst_clear(u64 record_id);
>  int arch_apei_enable_cmcff(struct acpi_hest_header *hest_hdr, void *data);
>  void arch_apei_report_mem_error(int sev, struct cper_sec_mem_err *mem_err);
>  void arch_apei_flush_tlb_one(unsigned long addr);
> +pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr);
>  
>  #endif
>  #endif

This doesn't compile :(

/home/matt/src/kernels/efi/arch/x86/kernel/acpi/apei.c:64:24: error: static declaration of ‘arch_apei_get_mem_attribute’ follows non-static declaration
 static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
                        ^
In file included from /home/matt/src/kernels/efi/arch/x86/kernel/acpi/apei.c:15:0:
/home/matt/src/kernels/efi/include/acpi/apei.h:48:10: note: previous declaration of ‘arch_apei_get_mem_attribute’ was here
 pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr);
          ^
/home/matt/src/kernels/efi/arch/x86/kernel/acpi/apei.c: In function ‘arch_apei_get_mem_attribute’:
/home/matt/src/kernels/efi/arch/x86/kernel/acpi/apei.c:80:2: error: incompatible types when initializing type ‘long unsigned int’ using type ‘pgprot_t’
  return __pgprot(PAGE_KERNEL);

-- 
Matt Fleming, Intel Open Source Technology Center
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