Re: [PATCH v7 11/14] KVM: Register/unregister the guest private memory regions

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

On Tue, Jul 19, 2022 at 04:23:52PM +0200, Gupta, Pankaj wrote:
> 
> > > > +bool __weak kvm_arch_private_mem_supported(struct kvm *kvm)
> > > > +{
> > > > +	return false;
> > > > +}
> > > 
> > > Does this function has to be overriden by SEV and TDX to support the private
> > > regions?
> > 
> > Yes it should be overridden by architectures which want to support it.
> 
> o.k
> > 
> > > 
> > > > +
> > > >    static int check_memory_region_flags(const struct kvm_user_mem_region *mem)
> > > >    {
> > > >    	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
> > > > @@ -4689,6 +4729,22 @@ static long kvm_vm_ioctl(struct file *filp,
> > > >    		r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
> > > >    		break;
> > > >    	}
> > > > +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM
> > > > +	case KVM_MEMORY_ENCRYPT_REG_REGION:
> > > > +	case KVM_MEMORY_ENCRYPT_UNREG_REGION: {
> > > > +		struct kvm_enc_region region;
> > > > +
> > > > +		if (!kvm_arch_private_mem_supported(kvm))
> > > > +			goto arch_vm_ioctl;
> > > > +
> > > > +		r = -EFAULT;
> > > > +		if (copy_from_user(&region, argp, sizeof(region)))
> > > > +			goto out;
> > > > +
> > > > +		r = kvm_vm_ioctl_set_encrypted_region(kvm, ioctl, &region);
> > > 
> > > this is to store private region metadata not only the encrypted region?
> > 
> > Correct.
> 
> Sorry for not being clear, was suggesting name change of this function from:
> "kvm_vm_ioctl_set_encrypted_region" to "kvm_vm_ioctl_set_private_region"

Though I don't have strong reason to change it, I'm fine with this and
this name matches the above kvm_arch_private_mem_supported perfectly.

Thanks,
Chao
> 
> > 
> > > 
> > > Also, seems same ioctl can be used to put other regions (e.g firmware, later
> > > maybe DAX backend etc) into private memory?
> > 
> > Possibly. Depends on what exactly the semantics is. If just want to set
> > those regions as private current code already support that.
> 
> Agree. Sure!
> 
> 
> Thanks,
> Pankaj