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From:   Andi Kleen <ak@linux.intel.com>
To:     Christophe de Dinechin <cdupontd@redhat.com>
Cc:     "Kirill A. Shutemov" <kirill@shutemov.name>,
        David Hildenbrand <david@redhat.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Sean Christopherson <seanjc@google.com>,
        Jim Mattson <jmattson@google.com>,
        David Rientjes <rientjes@google.com>,
        "Edgecombe\, Rick P" <rick.p.edgecombe@intel.com>,
        "Kleen\, Andi" <andi.kleen@intel.com>,
        "Yamahata\, Isaku" <isaku.yamahata@intel.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [RFCv1 7/7] KVM: unmap guest memory using poisoned pages
In-Reply-To: <C841A818-7BBE-48B5-8CCB-1F8850CA52AD@redhat.com> (Christophe de
        Dinechin's message of "Wed, 7 Apr 2021 15:31:28 +0200")
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        <20210402152645.26680-8-kirill.shutemov@linux.intel.com>
        <c5f2580d-0733-4523-d1e8-c43b487f0aaf@redhat.com>
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        <d94d3042-098a-8df7-9ef6-b869851a4134@redhat.com>
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        <C841A818-7BBE-48B5-8CCB-1F8850CA52AD@redhat.com>
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Date:   Wed, 07 Apr 2021 07:09:00 -0700
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Christophe de Dinechin <cdupontd@redhat.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