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Subject: Re: [PATCH] x86: efi/e820 table merge fix
From: Huang Ying <ying.huang@intel.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Cliff Wickman <cpw@sgi.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "mingo@elte.hu" <mingo@elte.hu>,
       "yinghai@kernel.org" <yinghai@kernel.org>
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Date: Wed, 17 Jun 2009 09:44:59 +0800
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On Wed, 2009-06-17 at 09:38 +0800, H. Peter Anvin wrote:
> Huang Ying wrote:
> > On Wed, 2009-06-17 at 05:43 +0800, Cliff Wickman wrote:
> >> From: Cliff Wickman <cpw@sgi.com>
> >> --- linux.orig/arch/x86/kernel/efi.c
> >> +++ linux/arch/x86/kernel/efi.c
> >> @@ -240,10 +240,35 @@ static void __init do_add_efi_memmap(voi
> >>  		unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
> >>  		int e820_type;
> >>  
> >> -		if (md->attribute & EFI_MEMORY_WB)
> >> -			e820_type = E820_RAM;
> >> -		else
> >> +		switch (md->type) {
> >> +		case EFI_LOADER_CODE:
> >> +		case EFI_LOADER_DATA:
> >> +		case EFI_BOOT_SERVICES_CODE:
> >> +		case EFI_BOOT_SERVICES_DATA:
> >> +		case EFI_CONVENTIONAL_MEMORY:
> >> +			if (md->attribute & EFI_MEMORY_WB)
> >> +				e820_type = E820_RAM;
> >> +			else
> >> +				e820_type = E820_RESERVED;
> >> +			break;
> > 
> > Why does BIOS mark memory region without EFI_MEMORY_WB as these types?
> > Any example?
> > 
> Probably not, but if it does, it's broken, and the memory should be
> ignored. The original code had the EFI_MEMORY_WB check already, so it
> seems prudent to keep it.

Maybe we need a real life example for that "fix". And attribute that to
the vendor in comments.

Best Regards,
Huang Ying