linux-kernel - Re: [Xen-devel] [PATCH 06/11] xen/mmu: For 64-bit do not call xen_map_identity

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Date:	Fri, 17 Aug 2012 13:45:49 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [Xen-devel] [PATCH 06/11] xen/mmu: For 64-bit do not call
 xen_map_identity_early

On Fri, Aug 17, 2012 at 06:41:23PM +0100, Stefano Stabellini wrote:
> On Thu, 16 Aug 2012, Konrad Rzeszutek Wilk wrote:
> > B/c we do not need it. During the startup the Xen provides
> > us with all the memory mapped that we need to function.
> 
> Shouldn't we check to make sure that is actually true (I am thinking at
> nr_pt_frames)?

I was looking at the source code (hypervisor) to figure it out and
that is certainly true.


> Or is it actually stated somewhere in the Xen headers?

Couldn't find it, but after looking so long at the source code
I didn't even bother looking for it.

Thought to be honest - I only looked at how the 64-bit pagetables
were set up, so I didn't dare to touch the 32-bit. Hence the #ifdef

> 
> 
> 
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > ---
> >  arch/x86/xen/mmu.c |   11 +++++------
> >  1 files changed, 5 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> > index 7247e5a..a59070b 100644
> > --- a/arch/x86/xen/mmu.c
> > +++ b/arch/x86/xen/mmu.c
> > @@ -84,6 +84,7 @@
> >   */
> >  DEFINE_SPINLOCK(xen_reservation_lock);
> >  
> > +#ifdef CONFIG_X86_32
> >  /*
> >   * Identity map, in addition to plain kernel map.  This needs to be
> >   * large enough to allocate page table pages to allocate the rest.
> > @@ -91,7 +92,7 @@ DEFINE_SPINLOCK(xen_reservation_lock);
> >   */
> >  #define LEVEL1_IDENT_ENTRIES	(PTRS_PER_PTE * 4)
> >  static RESERVE_BRK_ARRAY(pte_t, level1_ident_pgt, LEVEL1_IDENT_ENTRIES);
> > -
> > +#endif
> >  #ifdef CONFIG_X86_64
> >  /* l3 pud for userspace vsyscall mapping */
> >  static pud_t level3_user_vsyscall[PTRS_PER_PUD] __page_aligned_bss;
> > @@ -1628,7 +1629,7 @@ static void set_page_prot(void *addr, pgprot_t prot)
> >  	if (HYPERVISOR_update_va_mapping((unsigned long)addr, pte, 0))
> >  		BUG();
> >  }
> > -
> > +#ifdef CONFIG_X86_32
> >  static void __init xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
> >  {
> >  	unsigned pmdidx, pteidx;
> > @@ -1679,7 +1680,7 @@ static void __init xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
> >  
> >  	set_page_prot(pmd, PAGE_KERNEL_RO);
> >  }
> > -
> > +#endif
> >  void __init xen_setup_machphys_mapping(void)
> >  {
> >  	struct xen_machphys_mapping mapping;
> > @@ -1765,14 +1766,12 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
> >  	/* Note that we don't do anything with level1_fixmap_pgt which
> >  	 * we don't need. */
> >  
> > -	/* Set up identity map */
> > -	xen_map_identity_early(level2_ident_pgt, max_pfn);
> > -
> >  	/* Make pagetable pieces RO */
> >  	set_page_prot(init_level4_pgt, PAGE_KERNEL_RO);
> >  	set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
> >  	set_page_prot(level3_kernel_pgt, PAGE_KERNEL_RO);
> >  	set_page_prot(level3_user_vsyscall, PAGE_KERNEL_RO);
> > +	set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO);
> >  	set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
> >  	set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
> >  
> > -- 
> > 1.7.7.6
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@...ts.xen.org
> > http://lists.xen.org/xen-devel
> > 
> --
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