lkcd-devel

[Rajesham G. <raj...@ya...>]

Sachin/Alek,

I also faced the very similar issue & Sachin analysis 
is correct. The fix that is working for me is:

diff -urN -X kernel-2.6.7-dontdiff
kernel-2.6.7-orig/drivers/dump/dump_x8664.c
kernel-2.6.7-modif/drivers/dump/dump_x8664.c
--- kernel-2.6.7-orig/drivers/dump/dump_x8664.c
+++ kernel-2.6.7-modif/drivers/dump/dump_x8664.c
@@ -330,7 +330,8 @@
 int
 __dump_page_valid(unsigned long index)
 {
-       if (!pfn_valid(index))
+       if (!pfn_valid(index) ||
+           !kern_addr_valid((unsigned
long)pfn_to_kaddr(index)))
                return 0;

        return page_is_ram(index);



Rajesham


--- Sachin Sant <sa...@in...> wrote:
> Aleks , my guess is that you have more than 4G of
> RAM on the system.
> I recently came across this problem with lkcd on
> machines having ram > 
> 4G . When the RAM is > 4 GB a 64 k chunk of RAM is
> reserved for IOMMU
> pages. This chunk resides in low memory [ typically
> 0x4000000 - 
> 0x7ffffff] hence page_is_ram fails to find this
> hole.
> If the ammount of memory is restricted to less than
> 4G the dump will 
> work fine.
> 
> Give the attached patch a try. This is for 2.6 based
> kernel. Let me know 
> if it sounds ok.
> 
> Aleksandar Markovic wrote:
> > Hi, Sachin,
> > 
> > I am setting up lkcd on several x86_64 machines,
> and
> > it works fine on EM64T machines, however lkcd
> crashes
> > during panic handling on Opterons, producing
> unusable
> > dumps.
> > 
> > The crash is in memcpy, during copying a page into
> > internal buffer. Call stack is:
> > 
> > memcpy()
> > dump_lcrash_add_data()
> > dump_generic_save_data()
> > dump_execute_savedump()
> > dump_generic_execute()
> > dump_execute()
> > manual_handle_crashdump()
> > capable()
> > sys_ioctl()
> > 
> > Ir looks to me that for some reason LKCD tries to
> dump
> > a page that is not suitable for dumping. This is
> > related to code containing page_is_ram(), etc.
> > 
> > I can gicve you more info, but I was wondering
> maybe
> > you can tell me some hint on what to do.
> > 
> > Thanks!
> > 
> > Aleks
> > 
> > 
> > 
> > 
> > __________________________________________________
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> > 
> 
> 
> -- 
> Thanks
> -Sachin
> -----------------------------------
> Sachin Sant
> Linux Technology Center
> IBM Software Lab
> Bangalore, INDIA.
> 
> sa...@in...
> Ph: 91-80-5044647
> -----------------------------------
> > diff -urNpa old/arch/x86_64/kernel/pci-gart.c
> new/arch/x86_64/kernel/pci-gart.c
> --- old/arch/x86_64/kernel/pci-gart.c	2005-01-24
> 15:21:50.000000000 +0530
> +++ new/arch/x86_64/kernel/pci-gart.c	2005-03-23
> 16:43:13.335241840 +0530
> @@ -621,6 +621,9 @@
> EXPORT_SYMBOL(pci_dma_supported);
>  EXPORT_SYMBOL(no_iommu);
>  EXPORT_SYMBOL(force_iommu); 
>  EXPORT_SYMBOL(bad_dma_address);
> +/* Export the following so that the dump driver can
> use it */
> +EXPORT_SYMBOL(iommu_bus_base);
> +EXPORT_SYMBOL(iommu_size);
>  
>  static __init unsigned long
> check_iommu_size(unsigned long aper, u64 aper_size)
>  { 
> diff -urNpa old/drivers/dump/dump_x8664.c
> new/drivers/dump/dump_x8664.c
> --- old/drivers/dump/dump_x8664.c	2005-01-24
> 15:22:26.000000000 +0530
> +++ new/drivers/dump/dump_x8664.c	2005-03-23
> 16:41:56.000000000 +0530
> @@ -335,6 +335,10 @@ __dump_cleanup(void)
>  	return;
>  }
>  
> +#ifdef CONFIG_GART_IOMMU
> +extern unsigned long iommu_size;
> +extern unsigned long iommu_bus_base;
> +#endif
>  extern int page_is_ram(unsigned long);
>  
>  /*
> @@ -347,6 +351,13 @@ __dump_page_valid(unsigned long
> index)
>  	if (!pfn_valid(index))
>  		return 0;
>  
> +        /* See if the page falls in the IOMMU hole
> */
> +#ifdef CONFIG_GART_IOMMU
> +        if (((index << PAGE_SHIFT) >=
> iommu_bus_base) &&
> +            ((index << PAGE_SHIFT) <
> (iommu_bus_base + iommu_size)))
> +                return 0;
> +#endif
> +
>  	return page_is_ram(index);
>  }
>  
> 

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