Re: [PATCH v2 29/30] KVM: PPC: add KVM_SET_ONE_REG/KVM_GET_ONE_REG to async ioctl

[Simon Guo <wei.guo.simon@xxxxxxxxx>]

Hi Paul,
On Tue, May 15, 2018 at 04:15:26PM +1000, Paul Mackerras wrote:
> On Wed, Feb 28, 2018 at 01:52:37AM +0800, wei.guo.simon@xxxxxxxxx wrote:
> > From: Simon Guo <wei.guo.simon@xxxxxxxxx>
> > 
> > In both HV/PR KVM, the KVM_SET_ONE_REG/KVM_GET_ONE_REG ioctl should
> > be able to perform without load vcpu. This patch adds
> > KVM_SET_ONE_REG/KVM_GET_ONE_REG implementation to async ioctl
> > function.
> > 
> > Signed-off-by: Simon Guo <wei.guo.simon@xxxxxxxxx>
> > ---
> >  arch/powerpc/kvm/powerpc.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> > index 7987fa3..6afd004 100644
> > --- a/arch/powerpc/kvm/powerpc.c
> > +++ b/arch/powerpc/kvm/powerpc.c
> > @@ -1619,6 +1619,19 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp,
> >  			return -EFAULT;
> >  		return kvm_vcpu_ioctl_interrupt(vcpu, &irq);
> >  	}
> > +
> > +	if ((ioctl == KVM_SET_ONE_REG) || (ioctl == KVM_GET_ONE_REG)) {
> > +		struct kvm_one_reg reg;
> > +
> > +		if (copy_from_user(&reg, argp, sizeof(reg)))
> > +			return -EFAULT;
> > +
> > +		if (ioctl == KVM_SET_ONE_REG)
> > +			return kvm_vcpu_ioctl_set_one_reg(vcpu, &reg);
> > +		else
> > +			return kvm_vcpu_ioctl_get_one_reg(vcpu, &reg);
> > +	}
> > +
> >  	return -ENOIOCTLCMD;
> >  }
> 
> This seems dangerous to me, since now we can have set/get one_reg
> running in parallel with vcpu execution.  Is there a really compelling
> reason to do this?  If not I'd rather not make this change.

I will remove this patch.
Thanks,
- Simon