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

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

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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