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

[Borislav Petkov]

On Tue, Nov 23, 2021 at 03:36:35PM +0000, Sean Christopherson wrote:
> Kirill posted a few RFCs that did exactly that.  It's definitely a viable approach,
> but it's a bit of a dead end,

One thing at a time...

> e.g. doesn't help solve page migration,

AFAICR, that needs a whole explicit and concerted effort with the
migration helper - that was one of the approaches, at least, guest's
explicit involvement, remote attestation and a bunch of other things...

> is limited to struct page

I'm no mm guy so maybe you can elaborate further.

> doesn't capture which KVM guest owns the memory, etc...

So I don't think we need this for the problem at hand. But from the
sound of it, it probably is a good idea to be able to map the guest
owner to the memory anyway.

> https://lore.kernel.org/kvm/20210416154106.23721-1-kirill.shutemov@xxxxxxxxxxxxxxx/

Right, there it is in the last patch.

Hmmkay, so we need some generic machinery which unmaps memory from
the host kernel's pagetables so that it doesn't do any stray/unwanted
accesses to it. I'd look in the direction of mm folks for what to do
exactly, though.

Thx.

-- 
Regards/Gruss,
    Boris.

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