On 18.10.24 09:15, Patrick Roy wrote:
On Thu, 2024-10-17 at 20:18 +0100, Jason Gunthorpe wrote:
On Thu, Oct 17, 2024 at 03:11:10PM -0400, Peter Xu wrote:
On Thu, Oct 17, 2024 at 02:10:10PM -0300, Jason Gunthorpe wrote:
If so, maybe that's a non-issue for non-CoCo, where the VM object /
gmemfd object (when created) can have a flag marking that it's
always shared and can never be converted to private for any page
within.
What is non-CoCo? Does it include the private/shared concept?
I used that to represent the possible gmemfd use cases outside confidential
computing.
So the private/shared things should still be around as fundamental property
of gmemfd, but it should be always shared and no convertion needed for the
whole lifecycle of the gmemfd when marked !CoCo.
But what does private mean in this context?
Is it just like a bit of additional hypervisor security that the page
is not mapped anyplace except the KVM stage 2 and the hypervisor can
cause it to become mapped/shared at any time? But the guest has no
idea about this?
Jason
Yes, this is pretty much exactly what I'm after when I say "non-CoCo".
It's likely not what Peter meant, though.
I think there are three scenarios:
(a) Secure CoCo VMs: private is protected by HW
(b) Semi-secured non-CoCo VMs: private is removed from the directmap
(c) Non-CoCo VMs: only shared memory
Does that match what you have in mind? Are there other cases?
--
Cheers,
David / dhildenb
