On Tue, Nov 23, 2021, Borislav Petkov wrote:

On Mon, Nov 22, 2021 at 02:51:35PM -0800, Dave Hansen wrote:

quoted

By "supporting", do you mean doing something functional?  I don't really
care if ptrace() to guest private memory returns -EINVAL or whatever.
The most important thing is not crashing the host.

Also, as Sean mentioned, this isn't really about ptrace() itself.  It's
really about ensuring that no kernel or devices accesses to guest
private memory can induce bad behavior.

I keep repeating this suggestion of mine that we should treat
guest-private pages as hw-poisoned pages which have experienced a
uncorrectable error in the past.

mm already knows how to stay away from those.

Kirill posted a few RFCs that did exactly that.  It's definitely a viable approach,
but it's a bit of a dead end, e.g. doesn't help solve page migration, is limited to
struct page, doesn't capture which KVM guest owns the memory, etc...

https://lore.kernel.org/kvm/20210416154106.23721-1-kirill.shutemov@linux.intel.com/ (local)