Re: [RFC][PATCH -mm 3/4] Hibernation: Use temporary kernel text mapping during restore on x86_64

[Pavel Machek <pavel@ucw.cz>]

Hi!

> Use temporary page tables for the kernel text mapping during hibernation restore
> on x86_64.
> 
> Without the patch, the original boot kernel's page tables that represent the
> kernel text mapping are used while the core of the image kernel is being
> restored.  However, in principle, if the boot kernel is not identical to the
> image kernel, the location of these page tables in the image kernel need not be
> the same, so we should create a safe copy of the kernel text mapping prior to
> restoring the core of the image kernel.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> ---
>  arch/x86_64/kernel/suspend.c |   41 ++++++++++++++++++++++++++++++++++-------
>  1 file changed, 34 insertions(+), 7 deletions(-)
> 
> Index: linux-2.6.23-rc3/arch/x86_64/kernel/suspend.c
> ===================================================================
> --- linux-2.6.23-rc3.orig/arch/x86_64/kernel/suspend.c	2007-08-14 01:06:28.000000000 +0200
> +++ linux-2.6.23-rc3/arch/x86_64/kernel/suspend.c	2007-08-14 01:06:34.000000000 +0200
> @@ -175,7 +175,7 @@ static int res_phys_pud_init(pud_t *pud,
>  
>  			if (paddr >= end)
>  				break;
> -			pe = _PAGE_NX | _PAGE_PSE | _KERNPG_TABLE | paddr;
> +			pe = __PAGE_KERNEL_LARGE | paddr;
>  			pe &= __supported_pte_mask;
>  			set_pmd(pmd, __pmd(pe));
>  		}
> @@ -183,25 +183,42 @@ static int res_phys_pud_init(pud_t *pud,
>  	return 0;
>  }
>  
> +static int res_kernel_text_pud_init(pud_t *pud, unsigned long start)
> +{
> +	pmd_t *pmd;
> +	unsigned long paddr;
> +
> +	pmd = (pmd_t *)get_safe_page(GFP_ATOMIC);
> +	if (!pmd)
> +		return -ENOMEM;
> +	set_pud(pud + pud_index(start), __pud(__pa(pmd) | _KERNPG_TABLE));
> +	for (paddr = 0; paddr < KERNEL_TEXT_SIZE; pmd++, paddr += PMD_SIZE) {

Should we have something like "< max possible kernel size here"? IOW
this needs to cover both suspend _and_ resume kernels, no?
									Pavel
-- 
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