From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH] x86: drop setup_idle_pagetable()
Date: Wed, 12 Jun 2013 16:06:47 +0100
Message-ID: <51B88E87.7020507@citrix.com>
References: <51B8A8F302000078000DDA29@nat28.tlf.novell.com>
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To: Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>, "Keir (Xen.org)" <keir@xen.org>, xen-devel <xen-devel@lists.xen.org>
List-Id: xen-devel@lists.xenproject.org

On 12/06/13 15:59, Jan Beulich wrote:
> With vcpu->domain->arch.perdomain_l3_pg no longer getting set up for
> the idle domain, this creates an invalid L4 entry (due to translating
> a NULL struct page_info pointer to a physical address).
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

Is it perhaps prudent to extend some of the $FOO_from_page() macros to
guard against NULL pointers in debug builds?

~Andrew

>
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -185,7 +185,6 @@ static void __init init_idle_domain(void
>      scheduler_init();
>      set_current(idle_vcpu[0]);
>      this_cpu(curr_vcpu) = current;
> -    setup_idle_pagetable();
>  }
>  
>  void __devinit srat_detect_node(int cpu)
> --- a/xen/arch/x86/x86_64/mm.c
> +++ b/xen/arch/x86/x86_64/mm.c
> @@ -810,14 +810,6 @@ void __init paging_init(void)
>      panic("Not enough memory for m2p table\n");    
>  }
>  
> -void __init setup_idle_pagetable(void)
> -{
> -    /* Install per-domain mappings for idle domain. */
> -    l4e_write(&idle_pg_table[l4_table_offset(PERDOMAIN_VIRT_START)],
> -              l4e_from_page(idle_vcpu[0]->domain->arch.perdomain_l3_pg,
> -                            __PAGE_HYPERVISOR));
> -}
> -
>  void __init zap_low_mappings(void)
>  {
>      BUG_ON(num_online_cpus() != 1);
> --- a/xen/include/asm-x86/page.h
> +++ b/xen/include/asm-x86/page.h
> @@ -286,7 +286,6 @@ extern l2_pgentry_t l2_identmap[4*L2_PAG
>  extern l1_pgentry_t l1_identmap[L1_PAGETABLE_ENTRIES],
>      l1_fixmap[L1_PAGETABLE_ENTRIES];
>  void paging_init(void);
> -void setup_idle_pagetable(void);
>  #endif /* !defined(__ASSEMBLY__) */
>  
>  #define _PAGE_PRESENT  _AC(0x001,U)
>
>
>