[Crash-utility] [PATCH] increase __PHYSICAL_MASK_SHIFT_XEN

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> The current value of __PHYSICAL_MASK_SHIFT_XEN in crash (40) is
> smaller than the kernel (52) since kernel commit 6f0e8bf167 (xen:
> support 52 bit physical addresses in pv guests).
> 
> This can cause x86_64_pud_offset() to lose the most significant
> bits of pgd_pte, leading to a failed xen_m2p() translation,
> resulting in crash failing with an error message like this:
>    crash: read error: physical address: ffffffffffffffff  type: "pud page"
> 
> Both Intel and AMD documentation mandate that unused physical
> address bits must be 0, so there is no need to explicitly mask them
> out with a mask narrower than the architecture limit of 52. This
> is also confirmed by this kernel commit: b83ce5ee91.
> 
> Increase the value of __PHYSICAL_MASK_SHIFT_XEN to 52.
> 
> Signed-off-by: Jiri Bohac <jbohac at suse.cz>

Looks good and tested ok with several old xen dumpfiles on hand.

Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>

Thanks,
Kazu


> 
> diff --git a/defs.h b/defs.h
> index e468b1d..848c1f6 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -3583,7 +3583,7 @@ struct arm64_stackframe {
>   *  PHYSICAL_PAGE_MASK changed (enlarged) between 2.4 and 2.6, so
>   *  for safety, use the 2.6 values to generate it.
>   */
> -#define __PHYSICAL_MASK_SHIFT_XEN     40
> +#define __PHYSICAL_MASK_SHIFT_XEN     52
>  #define __PHYSICAL_MASK_SHIFT_2_6     46
>  #define __PHYSICAL_MASK_SHIFT_5LEVEL  52
>  #define __PHYSICAL_MASK_SHIFT  (machdep->machspec->physical_mask_shift)
> 
> 
> --
> Jiri Bohac <jbohac at suse.cz>
> SUSE Labs, Prague, Czechia
> 
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