Re: kvm: RDTSCP on AMD

From: Eduardo Habkost
Date: Mon Dec 10 2018 - 14:47:30 EST

On Mon, Dec 10, 2018 at 07:41:53PM +0100, Borislav Petkov wrote:
> On Mon, Dec 10, 2018 at 04:37:30PM -0200, Eduardo Habkost wrote:
> > It isn't as simply as reverting commit 33b5e8c03ae7, but we can
> > surely re-add RDTSCP on pc-*-4.0 and newer.
> Sure. If you could only point me to an example how to add that to
> pc-*-4.0 and newer, I'll gladly cook up a patch and test it.

Sorry, I forgot to reply to this part.

See commit 33b5e8c03ae7 for reference. The differences will be:
* Instead of removing RDTSCP from builtin_x86_defs, you'll be adding it.
* Instead of adding rdtscp=on entries to PC_COMPAT_2_4, you'll
be adding rdtscp=off entries to PC_COMPAT_3_1.

PC_COMPAT_3_1 is added by the patch that creates the 4.0
machine-types. You can find it on my machine-next branch at: