Re: [Xen-devel] [PATCH 1/2] Revert "kexec/x86: do not map crash kernel area"

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.01.14 at 16:56, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
> 
> This reverts commit 7113a45451a9f656deeff070e47672043ed83664.

As indicated before - I don't think reverting is the right thing here.
Just add the necessary code in the same (or another, if more
suitable) place.

Jan

> The kexec code uses map_domain_page() on pages within the crash
> region, so this mapping is required if the crash region is within the
> direct map area.
> 
> Wthout this revert, loading a crash kernel may cause a fatal page
> fault when trying to zero the first control page allocated from the
> crash area.  The fault will occur on non-debug builds of Xen when the
> crash area is below 5 TiB (which will be most systems).
> 
> Reported-by: Don Slutz <dslutz@xxxxxxxxxxx>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
>  xen/arch/x86/setup.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 4833ca3..f07ee2b 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1097,7 +1097,9 @@ void __init __start_xen(unsigned long mbi_p)
>                           mod[i].mod_start,
>                           PFN_UP(mod[i].mod_end), PAGE_HYPERVISOR);
>      }
> -
> +    map_pages_to_xen((unsigned long)__va(kexec_crash_area.start),
> +                     kexec_crash_area.start >> PAGE_SHIFT,
> +                     PFN_UP(kexec_crash_area.size), PAGE_HYPERVISOR);
>      xen_virt_end = ((unsigned long)_end + (1UL << L2_PAGETABLE_SHIFT) - 1) &
>                     ~((1UL << L2_PAGETABLE_SHIFT) - 1);
>      destroy_xen_mappings(xen_virt_end, XEN_VIRT_START + 
> BOOTSTRAP_MAP_BASE);
> -- 
> 1.7.2.5
> 
> 
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