Re: [PATCH 0/8] x86/fpu: Remove CR0.TS support

From: Paul Bolle
Date: Tue Nov 01 2016 - 03:52:09 EST

On Tue, 2016-11-01 at 00:48 +0100, Borislav Petkov wrote:
> --- a/drivers/lguest/Kconfig
> +++ b/drivers/lguest/Kconfig

> Âconfig LGUEST
> Â tristate "Linux hypervisor example code"
> - depends on X86_32 && EVENTFD && TTY && PCI_DIRECT
> > + depends on X86_32 && EVENTFD && TTY && PCI_DIRECT && !MICROCODE
> Â select HVC_DRIVER
> Â ---help---
> Â ÂÂThis is a very simple module which allows you to run

LGUEST is the symbol for host support. The symbol for guest support is
LGUEST_GUEST and it lives in arch/x86/. Yes, it's a bit of a gotcha.

> but maybe the better fix is to hack in MSR emulation in lguest and
> intercept the *MSR accesses and do the writes/reads in the exception
> fixup and ...
> I haven't looked at the lguest code, of course and whether that's easily
> doable and whether it even makes sense and whether one should simply use
> qemu/kvm instead and, and, and...

Yeah, I thought about adding negative dependencies (eg, "!OLPC &&
!MICROCODE") too. But that would be contrary to the neat lguest goal to
be able to use the same kernel image as a host and a guest. At least, I
think that is one of its goals.

And as probably everybody capable of hacking on lguest (ie, other
people than me) came up with doubts similar to yours, these two issues
never got fixed. ÂÂ


Paul Bolle