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    From"Rafael J. Wysocki" <>
    SubjectRe: [discuss] Re: [PATCH][Fix][Resend] Fix Bug #4959: Page tables corrupted during resume on x86-64 (take 3)
    DateSat, 1 Oct 2005 09:47:25 +0200
    Hi,
    
    On Saturday, 1 of October 2005 03:25, Siddha, Suresh B wrote:
    > On Fri, Sep 30, 2005 at 08:51:08AM +0200, Rafael J. Wysocki wrote:
    > > On Friday, 30 of September 2005 07:26, Rafael J. Wysocki wrote:
    > > > Of course.  The .config is attached.  Generally, it's a non-SMP box, and commenting
    > > > out the zap_low_mappings((0) in setup_arch() makes the box boot again.
    > > 
    > > One more datapoint: The box boots if I move the zap_low_mappings((0)
    > > in the following way:
    > > 
    > > --- linux-2.6.14-rc2-git7.orig/arch/x86_64/kernel/setup.c	2005-09-30 07:39:35.000000000 +0200
    > > +++ linux-2.6.14-rc2-git7/arch/x86_64/kernel/setup.c	2005-09-30 08:31:20.000000000 +0200
    > > @@ -571,8 +571,6 @@
    > > 
    > >  	init_memory_mapping(0, (end_pfn_map << PAGE_SHIFT));
    > > 
    > > -	zap_low_mappings(0);
    > > -
    > >  #ifdef CONFIG_ACPI
    > >  	/*
    > >  	 * Initialize the ACPI boot-time table parser (gets the RSDP and SDT).
    > > @@ -680,6 +678,8 @@
    > >  		get_smp_config();
    > >  	init_apic_mappings();
    > >  #endif
    > > +	zap_low_mappings(0);
    > > +
    > 
    > Rafael, I still can't reproduce the issue. All of my EM64T systems are SMP
    > and looks like this problem happens only on an UP system. Looks like
    > there is some code flow which is still assuming the presence of low mappings.
    
    I think so too.
    
    > Andi, can you please see if you can reproduce this on one of your systems
    > similar to Rafael's.
    > 
    > >  	/*
    > >  	 * Request address space for all standard RAM and ROM resources
    > > 
    > > iHowever, if I place the zap_low_mappings((0) before the
    > > #define CONFIG_X86_LOCAL_APIC in line 673, it doesn't boot.
    > > 
    > > Certainly init_apic_mappings() is at fault.  Could that be a reult of a call to
    > > alloc_bootmem_pages()?.
    > 
    > I looked at init_apic_mappings() and didn't give me any clue.
    > alloc_bootmem_pages() don't use low direct mappings.
    
    OK, I'll try to narrow this a bit more.
    
    > > And one more: I have to boot with "noapic".
    > 
    > Are you saying "noapic" is the second data point or you need to use "noapic"
    > along with moving zap_low_mappings(0) 
    
    It could be the second data point.  I always boot with "noapic", since otherwise
    the sharing of IRQs is not handled properly on my box.
    
    Greetings
    Rafael
    -
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