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Date:   Fri, 13 Jan 2023 16:17:30 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Borislav Petkov <bp@alien8.de>
Cc:     Michael Roth <michael.roth@amd.com>, kvm@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org,
        linux-crypto@vger.kernel.org, x86@kernel.org,
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        dgilbert@redhat.com, jarkko@kernel.org, ashish.kalra@amd.com,
        harald@profian.com, Nikunj A Dadhania <nikunj@amd.com>
Subject: Re: [PATCH RFC v7 07/64] KVM: SEV: Handle KVM_HC_MAP_GPA_RANGE
 hypercall
Message-ID: <Y8GEGnmD90bySl8C@google.com>
References: <20221214194056.161492-1-michael.roth@amd.com>
 <20221214194056.161492-8-michael.roth@amd.com>
 <Y8GAGB73ZKElDYPI@zn.tnic>
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On Fri, Jan 13, 2023, Borislav Petkov wrote:
> On Wed, Dec 14, 2022 at 01:39:59PM -0600, Michael Roth wrote:
> > From: Nikunj A Dadhania <nikunj@amd.com>
> > 
> > KVM_HC_MAP_GPA_RANGE hypercall is used by the SEV guest to notify a
> > change in the page encryption status to the hypervisor.
> > 
> > The hypercall exits to userspace with KVM_EXIT_HYPERCALL exit code,
> > currently this is used for explicit memory conversion between
> > shared/private for memfd based private memory.
> 
> So Tom and I spent a while to figure out what this is doing...
> 
> Please explain in more detail what that is. Like the hypercall gets ignored for
> memslots which cannot be private...?

Don't bother, just drop the patch.  It's perfectly legal for userspace to create
the private memslot in response to a guest request.