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

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Date:	Thu, 23 Aug 2012 16:57:29 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"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 Thu, 23 Aug 2012, Konrad Rzeszutek Wilk wrote:
> >From 43fd7a5d9ecd31c2fc26851523cd4b5f7650fb39 Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Date: Thu, 12 Jul 2012 13:59:36 -0400
> Subject: [PATCH] xen/mmu: For 64-bit do not call xen_map_identity_early
> 
> B/c we do not need it. During the startup the Xen provides
                                            ^ remove the
> us with all the initial memory mapped that we need to function.
> 
> The initial memory mapped is up to the bootstack, which means
> we can reference using __ka up to 4.f):

Thanks, that is what I was looking for.

> (from xen/interface/xen.h):
> 
>  4. This the order of bootstrap elements in the initial virtual region:
>    a. relocated kernel image
>    b. initial ram disk              [mod_start, mod_len]
>    c. list of allocated page frames [mfn_list, nr_pages]
>    d. start_info_t structure        [register ESI (x86)]
>    e. bootstrap page tables         [pt_base, CR3 (x86)]
>    f. bootstrap stack               [register ESP (x86)]
> 
> (initial ram disk may be ommitted).
> 
> [v1: More comments in git commit]
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Acked-by: Stefano Stabellini <stefano.stabellini@...citrix.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
> 
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