Re: Cross vendor migration ideas

[Anthony Liguori <anthony@codemonkey.ws>]

Alexander Graf wrote:
> Hi,
>
> I was thinking a bit about cross vendor migration recently and since 
> we're doing open source development, I figured it might be a good idea 
> to talk to everyone about this.
>
> So why are we having a problem?
>
> In normal operation we don't. If we're running a 32-bit kernel, we can 
> use SYSENTER to jump from kernel<->userspace. If we're on a 64-bit 
> kernel with 64-bit userspace, every CPU supports SYSCALL. At least 
> Linux is being smart on this and does use exactly these two 
> capabilities in these two cases.
> But if we're running in compat mode (64-bit kernel with 32-bit 
> userspace), things differ. Intel supports only SYSENTER here, while 
> AMD only supports SYSCALL. Both can still use int80.

Obviously we can trap-and-emulate but that would be slow in a relatively 
fast past.

I wonder if patching is an option?

Regards,

Anthony Liguori