Vista - multibyte nops

Virtual PC 2007 does not allow guest operating systems to use multibyte
NOPs (0x0f 0x1f). Modern compilers and operating systems are starting
to use these NOPs as an optimization. We really need Virtual PC to
support this.
David

Hi David,

I seem to remember this issue - but did not know of any guest OS that
actually used this instruction. What are you running in a VM to hit this?

Cheers,
Benjamin Armstrong
============================
Windows Virtualization Program Manager
Blog: http://blogs.msdn.com/Virtual_PC_Guy
Book: http://tinyurl.com/ysxcbm

This posting is provided "AS IS" with no warranties, and confers no
rights. You assume all risk for your use.

David Sanders wrote:

Benjamin Armstrong [MSFT] wrote:Linux kernels 2.6.24 - 2.6.26 include this code depending on the options
you select when you build it.

Recent versions of the gnu assembler (like in Fedora 9) will generate
such code if the target is 686 or later and you use -mtune=x.

I have been in a heated discussion on the linux-kernel mailing list
about this and I think it will be fixed for 2.6.27 and later kernels.

On certain kernels you can get around the issue by a kernel boot-time
parameter (noreplace-paravirt) since the offending code is usually in
the Paravirtualization stuff. But on other kernels you can't boot at
all because of using the multibyte nops in other places.

It is important to fix it now before use of the multibyte nops becomes
too widespread.

David

I have been out of the office - but just came back to find that the VPC
team was aware of this and is currently investigating the best way to
address it. Thanks for the heads up though.

Cheers,
Benjamin Armstrong
============================
Windows Virtualization Program Manager
Blog: http://blogs.msdn.com/Virtual_PC_Guy
Book: http://tinyurl.com/ysxcbm

This posting is provided "AS IS" with no warranties, and confers no
rights. You assume all risk for your use.

David Sanders wrote:

Benjamin Armstrong [MSFT] wrote:Thanks.