Re: [Xen-devel] [Bug 198497] handle_mm_fault / xen_pmd_val / radix_tree_lookup_slot Null pointer

[Juergen Gross <jgross@suse.com>]

On 21/04/18 16:35, Matthew Wilcox wrote:
> On Fri, Apr 20, 2018 at 10:02:29AM -0600, Jan Beulich wrote:
>>>>>> Skylake 32bit PAE Dom0:
>>>>>> Bad swp_entry: 80000000
>>>>>> mm/swap_state.c:683: bad pte d3a39f1c(8000000400000000)
>>>>>>
>>>>>> Ivy Bridge 32bit PAE Dom0:
>>>>>> Bad swp_entry: 40000000
>>>>>> mm/swap_state.c:683: bad pte d3a05f1c(8000000200000000)
>>>>>>
>>>>>> Other 32bit DomU:
>>>>>> Bad swp_entry: 4000000
>>>>>> mm/swap_state.c:683: bad pte e2187f30(8000000200000000)
>>>>>>
>>>>>> Other 32bit:
>>>>>> Bad swp_entry: 2000000
>>>>>> mm/swap_state.c:683: bad pte ef3a3f38(8000000100000000)
> 
>> As said in my previous reply - both of the bits Andrew has mentioned can
>> only ever be set when the present bit is also set (which doesn't appear to
>> be the case here). The set bits above are actually in the range of bits
>> designated to the address, which Xen wouldn't ever play with.
> 
> Is it relevant that all the crashes we've seen are with PAE in the guest?
> Is it possible that Xen thinks the guest is not using PAE?
> 

All Xen 32-bit PV guests are using PAE. Its part of the PV ABI.


Juergen