Re: [Xen-devel] Kernel panic with tboot E820_UNUSABLE region

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.05.13 at 18:49, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> On 14/05/13 15:46, Jan Beulich wrote:
>>>>> On 14.05.13 at 16:33, Aurelien Chartier <aurelien.chartier@xxxxxxxxxx> 
>>>>> wrote:
>>> Calls to update_va_mapping show the following error messages (with mfn
>>> going from 800 to 974):
>>>
>>> (XEN) mm.c:911:d0 Error getting mfn 800 (pfn 5555555555555555) from L1
>>> entry 0000000000800463 for l1e_owner=0, pg_owner=0
>> 
>> Yes, the kernel has no business mapping that region, and the
>> hypervisor rightly refuses the attempt.
> 
> Ok, so this is Xen checking the new PTE supplied in the
> update_va_mapping hypercall and saying no.
> 
> I think there are two things the kernel can do here.
> 
> a) Change the type of UNUSABLE regions to RAM.
> 
> b) Release pages overlapping UNUSABLE regions, destroy their mapping and
> clear/invalidate the region in the p2m.
> 
> Option a) is probably the easiest.

But the wrong one - no matter what the kernel changes the region
type to, Xen will still know it as UNUSABLE, and refuse the
mapping.

Jan


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