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

[Chao Peng]

On Tue, Jul 19, 2022 at 10:00:23AM +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.

> 
> > +
> >   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.

> 
> 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.

Chao
> 
> > +		break;
> > +	}
> > +#endif
> >   	case KVM_GET_DIRTY_LOG: {
> >   		struct kvm_dirty_log log;
> > @@ -4842,6 +4898,7 @@ static long kvm_vm_ioctl(struct file *filp,
> >   		r = kvm_vm_ioctl_get_stats_fd(kvm);
> >   		break;
> >   	default:
> > +arch_vm_ioctl:
> >   		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
> >   	}
> >   out:
>