Re: [Xen-devel] arch_init_memory() change

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

The code in arch/x86/setup.c with comment "Ensure all E820 RAM regions are
page-aligned and -sized" is supposed to fix this. In this case it should
turn the E820 entry into a zero-sized entry that is then discarded when the
e820 map is sanitized. Are you running a version of Xen that's missing this
code?

 -- Keir

On 22/6/07 17:28, "Altobelli, David" <david.altobelli@xxxxxx> wrote:

> In xen/arch/x86/mm.c, arch_init_memory() does not follow the same logic
> as find_max_pfn().  If a 4k non page aligned E820_RAM entry exists as
> the last RAM entry in the e820 map, it will be skipped by
> find_max_pfn(), but not by arch_init_memory(), triggering BUG_ON(pfn !=
> max_page).
> 
> The logic in arch_init_memory() could be changed to mirror
> find_max_pfn():
> --- xen/arch/x86/mm.c.orig      2007-06-22 10:10:19.000000000 -0500
> +++ xen/arch/x86/mm.c   2007-06-22 10:11:39.000000000 -0500
> @@ -220,6 +220,8 @@ void arch_init_memory(void)
>          /* Every page from cursor to start of next RAM region is I/O.
> */
>          rstart_pfn = PFN_UP(e820.map[i].addr);
>          rend_pfn   = PFN_DOWN(e820.map[i].addr + e820.map[i].size);
> +        if (rstart_pfn >= rend_pfn)
> +            continue;
>          for ( ; pfn < rstart_pfn; pfn++ )
>          {
>              BUG_ON(!mfn_valid(pfn));
> 
> But I think this breaks the sharing logic.  It might be better to just
> remove the BUG_ON():
> --- xen/arch/x86/mm.c.orig      2007-06-22 10:10:19.000000000 -0500
> +++ xen/arch/x86/mm.c   2007-06-22 11:20:42.000000000 -0500
> @@ -229,7 +229,6 @@ void arch_init_memory(void)
>          /* Skip the RAM region. */
>          pfn = rend_pfn;
>      }
> -    BUG_ON(pfn != max_page);
> 
>      subarch_init_memory();
>  }
> 
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> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel



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