x86-64 32bit applications support discussion

x86-64 32bit applications support discussion

[Jerone Young]

	This thread is intended for discussion of 32bit application support
under x86-64 virtual domains. To all reading this is for development
purposes (x86-64 support is not done yet).
	
	I've been actively looking into 32bit application support for the
x86-64 Virutal Domains. I do have a question that I wanted to bring to
the list to start the discussion.

	Since the virtual domain & applications are all running in ring 3. Does
the hypervisor need to know how to tell the CPU when and when not to go
into compatibility mode to  run running 32bit applications properly
under virtual domains? As you may know while under Long mode you have
two sub modes: 64-bit mode & compatibility (for 32bit stuff). The
problem I see is that since we are in Long Mode the virutal domain needs
to tell CPU to go into the sub mode compatibility mode for it's 32
applications but does not have the access to do so. I'm not sure the
best way of going about this (new hypercall?) ?
	

-- 
Jerone Young
IBM Linux Technology Center
jyoung5@us.ibm.com
512-838-1157 (T/L: 678-1157)



-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click

Re: x86-64 32bit applications support discussion

[Kurt Garloff]

[-- Attachment #1: Type: text/plain, Size: 462 bytes --]

Hi,

On Mon, Mar 14, 2005 at 11:02:27AM -0600, Jerone Young wrote:
> 	Since the virtual domain & applications are all running in ring 3.

You mean the kernel is running in ring 3 as well?

> Does
> the hypervisor need to know how to tell the CPU when and when not to go
> into compatibility mode to  run running 32bit applications properly
> under virtual domains? 

I would think so.

Regards,
-- 
Kurt Garloff, Director SUSE Labs, Novell Inc.

[-- Attachment #2: Type: application/pgp-signature, Size: 189 bytes --]

Re: x86-64 32bit applications support discussion

[Kip Macy]

Segment protection checks don't work in long mode. So - yes.


On Mon, 14 Mar 2005 18:20:27 +0100, Kurt Garloff <garloff@suse.de> wrote:
> Hi,
> 
> On Mon, Mar 14, 2005 at 11:02:27AM -0600, Jerone Young wrote:
> >       Since the virtual domain & applications are all running in ring 3.
> 
> You mean the kernel is running in ring 3 as well?
> 
> > Does
> > the hypervisor need to know how to tell the CPU when and when not to go
> > into compatibility mode to  run running 32bit applications properly
> > under virtual domains?
> 
> I would think so.
> 
> Regards,
> --
> Kurt Garloff, Director SUSE Labs, Novell Inc.
> 
> 
>


-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click

RE: x86-64 32bit applications support discussion

[Nakajima, Jun]

Jerone Young wrote:
> 	This thread is intended for discussion of 32bit application
support
> under x86-64 virtual domains. To all reading this is for development
> purposes (x86-64 support is not done yet).
> 
> 	I've been actively looking into 32bit application support for
the
> x86-64 Virutal Domains. I do have a question that I wanted to bring to
> the list to start the discussion.
> 
> 	Since the virtual domain & applications are all running in ring
3.
> Does the hypervisor need to know how to tell the CPU when and when
> not to go into compatibility mode to  run running 32bit applications
> properly under virtual domains? As you may know while under Long mode
> you have two sub modes: 64-bit mode & compatibility (for 32bit
> stuff). The problem I see is that since we are in Long Mode the
> virutal domain needs to tell CPU to go into the sub mode
> compatibility mode for it's 32 applications but does not have the
> access to do so. I'm not sure the best way of going about this (new
> hypercall?) ? 
The switch_to_user hypercall should allow you to switch to compatibility
mode as long as you provide one for that. Look at struct switch_to_user
and the do_switch_to_user. Xenolinux will set the same cs as the native
x86-64 Linux does for 32-bit processes. 

Jun


-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_ide95&alloc_id\x14396&op=click