x86/paravirt: groundwork for 64-bit Xen support, fix #2

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...

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 <[email protected]>
Cc: xen-devel <[email protected]>
Cc: Stephen Tweedie <[email protected]>
Cc: Eduardo Habkost <[email protected]>
Cc: Mark McLoughlin <[email protected]>
Cc: Vegard Nossum <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Yinghai Lu <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 5c3305e0507861321e9a81a3f344f6e04c726956..b10b7f17ea58d414576ded22b3c1b713fb06d6b6 100644 (file)
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -320,7 +320,8 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long address, unsigned long end)
                }
 
                if (pmd_val(*pmd)) {
-                       phys_pte_update(pmd, address, end);
+                       if (!pmd_large(*pmd))
+                               phys_pte_update(pmd, address, end);
                        continue;
                }