RE: [Xen-ia64-devel] Floating-point software assist (FPSWA) on Xen-ia64 - Magenheimer, Dan (HP Labs Fort Collins) - com.xensource.lists.xen-ia64-devel

8 messages in com.xensource.lists.xen-ia64-develRE: [Xen-ia64-devel] Floating-point s...

From	Sent On	Attachments
Magenheimer, Dan (HP Labs Fort Collins)	26 Jan 2006 09:29
Yang, Fred	26 Jan 2006 13:36
Magenheimer, Dan (HP Labs Fort Collins)	26 Jan 2006 14:30
Yang, Fred	26 Jan 2006 16:58
Magenheimer, Dan (HP Labs Fort Collins)	26 Jan 2006 20:44
Yang, Fred	26 Jan 2006 22:49
Magenheimer, Dan (HP Labs Fort Collins)	29 Jan 2006 16:36
Xu, Anthony	05 Feb 2006 19:21

Subject:	RE: [Xen-ia64-devel] Floating-point software assist (FPSWA) on Xen-ia64
From:	Magenheimer, Dan (HP Labs Fort Collins) (dan....@hp.com)
Date:	01/26/2006 02:30:55 PM
List:	com.xensource.lists.xen-ia64-devel

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...@intel.com] Sent: Thursday, January 26, 2006 2:37 PM To: Magenheimer, Dan (HP Labs Fort Collins); xen-...@lists.xensource.com 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.