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

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Date:	Sat, 4 Oct 2008 17:35:56 +0800
From:	"huang ying" <huang.ying.caritas@...il.com>
To:	"Yinghai Lu" <yhlu.kernel@...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

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.

[...]
> --- linux-2.6.orig/arch/x86/kernel/efi_64.c
> +++ linux-2.6/arch/x86/kernel/efi_64.c
> @@ -46,8 +46,8 @@ static void __init early_mapping_set_exe
>  {
>        unsigned long num_pages;
>
> -       start &= PMD_MASK;
> -       end = (end + PMD_SIZE - 1) & PMD_MASK;
> +       start &= PAGE_MASK;
> +       end = (end + PAGE_SIZE - 1) & PAGE_MASK;
>        num_pages = (end - start) >> PAGE_SHIFT;
>        if (executable)
>                set_memory_x((unsigned long)__va(start), num_pages);

early_mapping_set_exe() may be called before page allocator is
available. Using PAGE_MASK may make set_memory_x() allocate new page,
while using PMD_MASK will not.

Best Regards,
Huang Ying
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