RE: [Xen-ia64-devel] Floating-point software assist (FPSWA) on Xen-ia64

["Yang, Fred" <fred.yang@xxxxxxxxx>]

How about minic how native Linux does for FPSWA instead for Xen to
handle extra FP stuff.

Somehow the FPSWA information should be passed to Domains for them to
map into their own address space.  It seems Domain0 doesn't get FPSWA
info, so will happen on DomainU.

Somehow how FPSWA info got passed to native kernel should be understood,
then Xen can also pass the info accordingly for Domains to map it.

-Fred

Magenheimer, Dan (HP Labs Fort Collins) wrote:
> OK, so no conflict with VT-I.
> 
> I'm thinking the best non-VTI implementation for now will
> be to call fpswa from inside Xen.  This will appear
> to guests as if all the complex floating point ops
> that were previously handled by FPSWA are now handled
> "in hardware".  The disadvantage of this approach is
> that uses of fpswa will not be able to be tracked and
> reported (as they are today in Linux/ia64) because the
> guest will never see them.
> 
> Any comments?
> 
> Dan
> 
>> -----Original Message-----
>> From: Yang, Fred [mailto:fred.yang@xxxxxxxxx]
>> Sent: Thursday, January 26, 2006 2:37 PM
>> To: Magenheimer, Dan (HP Labs Fort Collins);
>> xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: RE: [Xen-ia64-devel] Floating-point software assist (FPSWA)
>> on Xen-ia64 
>> 
>> For native, the platform firmware comes with build-in FPSWA.  If
>> there is a new FPSWA.efi presented in the disk, the firmware will
>> drop its default FPSWA. 
>> 
>> For DomainVTI to run, there is a Guest Firmware (GFW), with default
>> FPSWA build-in, presented to domain.
>> 
>> -Fred
>> 
>> There is Guest Firmware (GFW) used for DomainVTI.
>> Magenheimer, Dan (HP
>> Labs Fort Collins) wrote:
>>> Yongkang has discovered that some LTP tests fail
>>> because Xen/ia64 (non-VTI) does not support FPSWA.
>>> Non-support of FPSWA is a known problem that has
>>> been on the to-do list for some time:
>>> 
>>> 
>> http://lists.xensource.com/archives/html/xen-devel/2004-12/msg
>> 00382.html
>>> 
>>> but this is the first time that it has been seen
>>> in real (test) usage.
>>> 
>>> Yongkang says that the test works with VTI.  How does
>>> VTI handle FPSWA?  Is direct access to fpswa.efi provided
>>> to every domain or is fpswa.efi "owned" by the hypervisor
>>> and floating-point assist traps handled by Xen invisibly to domains?
>>> 
>>> A couple of related questions:  Is fpswa.efi re-entrant?
>>> Does fpswa.efi ever disable interrupts?
>>> 
>>> I don't think this will be hard to fix, but it would
>>> be best if the implementation is consistent between
>>> VTI and non-VTI.
>>> 
>>> Thanks,
>>> Dan
>>> 
>>> _______________________________________________
>>> Xen-ia64-devel mailing list
>>> Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-ia64-devel


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