Re: LOCKDEBUG kernel option crashes if vcpu > 1

[Roger Pau Monné <roger.pau%citrix.com@localhost>]

El 19/11/14 a les 19.54, Manuel Bouyer ha escrit:
> On Thu, Nov 20, 2014 at 01:11:45AM +0530, Cherry G. Mathew wrote:
>> Looking at pmap_growkernel(), it seems to be well placed for this ( I
>> see that you wrote the code for the early startup case ), although I
>> dislike the if() within a fairly hot codepath.
>>
>> I also just noticed in amd64/include/param.h:
>>
>> #ifndef XEN
>> /* Must be defined before cpu.h */
>> #define MAXCPUS 256
>> #endif
>>
>> which means that maxcpus is 32 for XEN ? (Not sure when this happened).
> 
> This is strange; I'm almost sure I tested it with more vcpus than that.

If you want to use more than 32 vcpus on a Xen PV guest you need to use
the VCPUOP_register_vcpu_info hypercall in order to register the
vcpu_info area for each vcpu > 32 (or simply all vcpus). This is because
the vcpu_info array in the shared_info page is limited to 32 elements.

Roger.