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
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