[PATCH v3 04/15] KVM: Add common infrastructure for KVM Userfaults

[Sean Christopherson]

On Wed, Jun 18, 2025, Oliver Upton wrote:
> On Wed, Jun 18, 2025 at 01:33:17PM -0700, Sean Christopherson wrote:
> > On Wed, Jun 18, 2025, Oliver Upton wrote:
> > And this path is other motiviation for returning a boolean.  To me, return "success"
> > when a uaccess fails looks all kinds of wrong:
> > 
> > 	if (__get_user(chunk, user_chunk))
> > 		return 0;
> 
> Yeah, that's gross. Although I would imagine we want to express
> "failure" here, game over, out to userspace for resolution. So maybe:
> 
> 	if (__get_user(chunk, user_chunk))
> 		return -EFAULT;

I toyed with that idea too, but if kvm_do_userfault() returns a value, that it
bugs me to no end that the callers blindly convert all failures to -EFAULT.  To
avoid that, callers would have to be:

	r = kvm_do_userfault(vcpu, &fault);
	if (r)
		return r;

And that just annoyed me. :-)  But I'm a-ok with that direction if that's
preferrable to the boolean return.