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

Jeremy Fitzhardinge
2008-06-26T19:03:19Z

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@citrix.com>
---
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;
}