Re: [PATCH 10/18 V2]: PVH xen: introduce vmx_pvh.c and pvh.c

[Mukesh Rathor <mukesh.rathor@oracle.com>]

On Mon, 18 Mar 2013 12:32:06 -0400
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:

> On Fri, Mar 15, 2013 at 05:41:45PM -0700, Mukesh Rathor wrote:
> > +            return 1;
> > +        }
> > +
> > +        new_cr0 &= ~HVM_CR0_GUEST_RESERVED_BITS;
> > +        /* ET is reserved and should be always be 1. */
> > +        new_cr0 |= X86_CR0_ET;
> > +
> > +        /* pvh cannot change to real mode */
> > +        if ( (new_cr0 & (X86_CR0_PE|X86_CR0_PG)) !=
> > (X86_CR0_PG|X86_CR0_PE) ) {
> > +            printk("PVH attempting to turn off PE/PG. CR0:%lx\n",
> > new_cr0);
> > +            return 1;
> > +        }
> > +        /* TS going from 1 to 0 */
> > +        if ( (old_cr0 & X86_CR0_TS) && ((new_cr0 &
> > X86_CR0_TS)==0) )
> > +            vmx_fpu_enter(vp);
> 
> Does this really happen? I thought in the PV mode you would be using
> the hypercalls for the fpu swap? Should it be print out an error
> saying something to the effect:
> 
> 	"PVH guest is using cr0 instead of the paravirt lazy FPU
> switch!" and include the EIP?

Yes. At present in linux PVH, we use native_clts and not xen_clts pv
ops call. But another PVH guest might not want to use hypercalls, right?

thanks,
Mukesh