Re: [RFC][PATCH] ignore set_cr3 GP fault in non-pae mode

[Ryan Harper <ryanh-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

* Nakajima, Jun <jun.nakajima-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> [2007-09-18 16:22]:
> Anthony Liguori wrote:
> > Ryan Harper wrote:
> > > Playing around with running VMware-server within a KVM guest and
> noticed
> > > that whenever we launch a VM within the guest, KVM reports a GP
> fault in
> > > set_cr3.  Removing the fault injection (raised for attempting to set
> > > reserved bits) for the non-pae case allows memtest to boot and run
> > > within VMWare Server, running in a KVM Linux guest.
> > > 
> > > This same test (Linux, VMware-server, booting/running memtest iso)
> works
> > > fine on bare-metal.  Thoughts?
> > > 
> > 
> > Setting reserved bits is different from setting MBZ bits since the
> > behaviors undefined.  If something as common as VMware is depending on
> > being able to set a reserved bit then perhaps the right thing to do
> from
> > KVM's perspective is to let it.
> > 
> > I'm curious if Zach or Jun have any comments about the right thing to
> do
> > here.
> > 
> 
> As long as the guest is protected mode (unlike the long mode), the Intel
> spec does _not_ say that reserved bits checking is enforced for CR3. As
> far as I looked at the AMD spec, looks like #GP is caused even in
> protected mode... Does the test work for AMD systems?

I ran my test on an AMD host.

> 
> > Regards,
> > 
> > Anthony Liguori
> > 
> 
> 
> Jun
> ---
> Intel Open Source Technology Center

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
ryanh-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org

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