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

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Tuesday, 21 August 2007 09:59, Pavel Machek wrote:
> 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"?

AFAICS, KERNEL_TEXT_SIZE == "max possible kernel text size".  This even is
documented. :-)

Greetings,
Rafael