[Xen-devel] Re: A shadow bug?

[Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>]

Hi,

At 16:49 +0800 on 14 Nov (1163522982), Li, Xin B wrote:
> Hi Tim,
> I'm running OLTP on x86_64 SMP FC5 HVM guest, but I saw this messages on
> guest console:
> 
> mysqld: Corrupted page table at address 2aaaae717000
> PGD 33ae0067 PUD 33ae1067 PMD 2ea4c067 PTE 0
> Bad pagetable: 000f [1] SMP

Ah; it looks like x86_64 linux doesn't handle spurious reserved-bit page
faults.  Does this patch fix things for you?

diff -r 032578b83641 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Tue Nov 14 10:39:49 2006 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c    Tue Nov 14 10:43:08 2006 +0000
@@ -2623,6 +2623,10 @@ static int sh_page_fault(struct vcpu *v,
              * Fall through to the normal fault handing logic */
             perfc_incrc(shadow_fault_fast_fail);
             SHADOW_PRINTK("fast path false alarm!\n");
+            /* Don't pass the reserved-bit bit: if we look at the fault 
+             * below and decide to pass it to the guest, the reserved-bit
+             * bit won't make sense there. */
+            regs->error_code &= ~PFEC_reserved_bit;
         }
     }
 #endif /* SHOPT_FAST_FAULT_PATH */


Cheers,

Tim.

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