Re: [Xen-devel] 3.1/2 live migration panic

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 22:25 +0000 on 17 Jan (1200608703), John Levon wrote:
> (XEN) Xen call trace:
> (XEN)    [<ffff828c801b26ba>] shadow_set_l1e+0x4f/0x14c
> (XEN)    [<ffff828c801b5efe>] sh_page_fault__shadow_4_guest_4+0x6fe/0xb9e
> (XEN)    [<ffff828c8016234f>] paging_fault+0x3c/0x3e
> (XEN)    [<ffff828c801622f9>] fixup_page_fault+0x22b/0x245
> (XEN)    [<ffff828c80162391>] do_page_fault+0x40/0x15c
> (XEN)    
> (XEN) Pagetable walk from ffff81ff80d64ff0:
> (XEN)  L4[0x103] = 00000001cb03f063 000000000000063b
> (XEN)  L3[0x1fe] = 00000001d358e067 00000000000005d4
> (XEN)  L2[0x006] = 0000000000000000 ffffffffffffffff 

Hmmm.  This is the same error, one function further down the chain,
which tells us something interesting.  In this case, the shadow l3e has
been written into the l3 linear map and then used successfully via the
l2 linear map to write the l2e, but is now missing when we come to the
l1 linear map.  Bizarre.

Either something has changed the sl4e or sl3e under our feet (surely not
- we have the shadow lock), or it could still be a missing TLB flush.
If we changed the sl4e (from one present entry to another) but didn't
flush the TLB it could cause this.

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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