[Xen-devel] Re: [PATCH 00 of 36] x86/paravirt: groundwork for 64-bit Xen support

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Ingo Molnar wrote:
> that fixed the build but now we've got a boot crash with this config:
>
>  time.c: Detected 2010.304 MHz processor.
>  spurious 8259A interrupt: IRQ7.
>  BUG: unable to handle kernel NULL pointer dereference at  0000000000000000
>  IP: [<0000000000000000>]
>  PGD 0
>  Thread overran stack, or stack corrupted
>  Oops: 0010 [1] SMP
>  CPU 0
>   
I don't know if this will fix this bug, but it's definitely a bugfix.  
It was trashing random pages by overwriting them with pagetables...
Subject: x86_64: memory mapping: don't trash large pmd mapping

Don't trash a large pmd's data when mapping physical memory.
This is a bugfix for "x86_64: adjust mapping of physical pagetables
to work with Xen".

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
arch/x86/mm/init_64.c |    3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

===================================================================
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -311,7 +311,8 @@
                }

                if (pmd_val(*pmd)) {
-                       phys_pte_update(pmd, address, end);
+                       if (!pmd_large(*pmd))
+                               phys_pte_update(pmd, address, end);
                        continue;
                }




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