linux-kernel - Re: [RFC PATCH] x86: make 64bit efi to use ioremap_cache for efi

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Date:	Sat, 4 Oct 2008 10:44:00 -0700
From:	"Yinghai Lu" <yinghai@...nel.org>
To:	"huang ying" <huang.ying.caritas@...il.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Huang Ying" <ying.huang@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] x86: make 64bit efi to use ioremap_cache for efi_ioremap

On Sat, Oct 4, 2008 at 2:35 AM, huang ying <huang.ying.caritas@...il.com> wrote:
> Hi, Yinghai,
>
> On Sat, Oct 4, 2008 at 2:23 PM, Yinghai Lu <yhlu.kernel@...il.com> wrote:
> [...]
>> --- linux-2.6.orig/arch/x86/kernel/efi.c
>> +++ linux-2.6/arch/x86/kernel/efi.c
>> @@ -475,10 +475,7 @@ void __init efi_enter_virtual_mode(void)
>>                size = md->num_pages << EFI_PAGE_SHIFT;
>>                end = md->phys_addr + size;
>>
>> -               if (PFN_UP(end) <= max_low_pfn_mapped)
>> -                       va = __va(md->phys_addr);
>> -               else
>> -                       va = efi_ioremap(md->phys_addr, size);
>> +               va = efi_ioremap(md->phys_addr, size);
>
> Using __va and efi_ioremap() here is to make EFI support compatible
> with kexec. Because EFI provide only efi_enter_virtual_mode(), no
> efi_leave_virtual_mode(), we should make EFI runtime memory area
> mapped to same virtual memory area in original kernel and kexeced
> kernel, so that the EFI runtime services can be used in kexeced
> kernel.

so need to make efi range all under direct-mapping like E820-RAM?

if so we need to update
e820_end_of_low_ram_pfn to return correct max_low_pfn, and then
max_low_pfn_mapped...

YH
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