linux-kernel - Re: [RFCv1 7/7] KVM: unmap guest memory using poisoned pages

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Message-ID: <87zgyauqyr.fsf@linux.intel.com>
Date:   Wed, 07 Apr 2021 07:09:00 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Christophe de Dinechin <cdupontd@...hat.com>
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        David Hildenbrand <david@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        "Edgecombe\, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen\, Andi" <andi.kleen@...el.com>,
        "Yamahata\, Isaku" <isaku.yamahata@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFCv1 7/7] KVM: unmap guest memory using poisoned pages

Christophe de Dinechin <cdupontd@...hat.com> writes:

> Is there even a theoretical way to restore an encrypted page e.g. from (host)
> swap without breaking the integrity check? Or will that only be possible with
> assistance from within the encrypted enclave?

Only the later.

You would need balloning. It's in principle possible, but currently
not implemented.

In general host swap without balloning is usually a bad idea anyways
because it often just swaps a lot of cache data that could easily be
thrown away instead.

-andi