Re: [PATCH v14 00/20] Introduce PVH domU support

[George Dunlap <george.dunlap@eu.citrix.com>]

On 08/11/13 15:41, George Dunlap wrote:
> On 04/11/13 17:34, Tim Deegan wrote:
>> At 17:23 +0000 on 04 Nov (1383582187), George Dunlap wrote:
>>> On 04/11/13 16:59, Konrad Rzeszutek Wilk wrote:
>>>>> This also means no support for "legacy" forced invalid ops -- only 
>>>>> native
>>>>> cpuid is supported in this series.
>>>> OK.
>>> (FWIW, support for legacy forced invalid ops was requested by Tim.)
>> I was worried about existing PV kernel code that used the fake-CPUID,
>> which would break if the 'core' kernel code went from PV to PVH.  But
>> I guess I could be convinced that such kernel code is buggy? Really,
>> the high-order bit was consistency.  The version I commented on
>> supported them for user-space but not for kernel, which seemed like
>> risking trouble for no benefit.
>
> Oh right -- I think Mukesh we do need to support forced invalid ops 
> for user space so that we can use the same xen tools binaries on PV 
> and PVH kernels.
>
> Hmm, Mukesh / Konrad, what tools are you actually thinking about 
> here?  Are these Oracle-specific tools?  I can't seem to find 
> XEN_CPUID or XEN_EMULATE_PREFIX anywhere in the tools/ directory of 
> the xen repo...

It's misc/xen-detect.c, for the curious (which helpfully does not use 
the macros above).

Handling forced invalid ops it is, then.

I think it would make sense to handle them in the plain HVM case as well 
-- that way xen-detect could also work inside of PVHVM domains.

  -George