[RFC PATCH 03/17] KVM: PPC64: booke: Add EPCR support in sregs

[Caraman Mihai Claudiu-B02008]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Wednesday, June 27, 2012 1:35 AM
> To: Caraman Mihai Claudiu-B02008
> Cc: kvm-ppc at vger.kernel.org; kvm at vger.kernel.org; linuxppc-
> dev at lists.ozlabs.org; qemu-ppc at nongnu.org
> Subject: Re: [RFC PATCH 03/17] KVM: PPC64: booke: Add EPCR support in
> sregs
> 
> On 06/25/2012 07:26 AM, Mihai Caraman wrote:
> > Add KVM_SREGS_E_64 feature and EPCR spr support in get/set sregs for
> > 64-bit hosts.
> >
> > Signed-off-by: Mihai Caraman <mihai.caraman at freescale.com>
> > ---
> >  arch/powerpc/kvm/booke.c |   14 ++++++++++++++
> >  1 files changed, 14 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c index
> > f9fa260..d15c4b5 100644
> > --- a/arch/powerpc/kvm/booke.c
> > +++ b/arch/powerpc/kvm/booke.c
> > @@ -1052,6 +1052,9 @@ static void get_sregs_base(struct kvm_vcpu *vcpu,
> >  	u64 tb = get_tb();
> >
> >  	sregs->u.e.features |= KVM_SREGS_E_BASE;
> > +#ifdef CONFIG_64BIT
> > +	sregs->u.e.features |= KVM_SREGS_E_64;0 #endif
> >
> >  	sregs->u.e.csrr0 = vcpu->arch.csrr0;
> >  	sregs->u.e.csrr1 = vcpu->arch.csrr1; @@ -1063,6 +1066,9 @@ static
> > void get_sregs_base(struct kvm_vcpu *vcpu,
> >  	sregs->u.e.dec = kvmppc_get_dec(vcpu, tb);
> >  	sregs->u.e.tb = tb;
> >  	sregs->u.e.vrsave = vcpu->arch.vrsave;
> > +#ifdef CONFIG_64BIT
> > +	sregs->u.e.epcr = vcpu->arch.epcr;
> > +#endif
> >  }
> >
> >  static int set_sregs_base(struct kvm_vcpu *vcpu, @@ -1071,6 +1077,11
> > @@ static int set_sregs_base(struct kvm_vcpu *vcpu,
> >  	if (!(sregs->u.e.features & KVM_SREGS_E_BASE))
> >  		return 0;
> >
> > +#ifdef CONFIG_64BIT
> > +	if (!(sregs->u.e.features & KVM_SREGS_E_64))
> > +		return 0;
> > +#endif
> 
> This means that a QEMU targeting a 32-bit guest won't be able to set any
> special registers, if it sets feature bits manually rather than getting
> them from GET_SREGS.

I had some concerns about his. I only check qemu ppc code which uses get/set
approach and I followed the BASE model. Now I see that qemu x86 set them manually :(
Why do we care if the caller set or not BASE?

-Mike