Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support

[Sean Christopherson]

On Tue, Nov 23, 2021, Borislav Petkov wrote:
> On Mon, Nov 22, 2021 at 02:51:35PM -0800, Dave Hansen wrote:
> > 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@xxxxxxxxxxxxxxx/