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From:   Fuad Tabba <tabba@google.com>
Date:   Mon, 6 Nov 2023 16:17:09 +0000
Message-ID: <CA+EHjTzc4zwN1atU1mSnbi3Lvb0c83MATQSk1uSWxae2iKi0aw@mail.gmail.com>
Subject: Re: [PATCH 27/34] KVM: selftests: Introduce VM "shape" to allow tests
 to specify the VM type
To:     Sean Christopherson <seanjc@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>, Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
        Huacai Chen <chenhuacai@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Anup Patel <anup@brainfault.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Xiaoyao Li <xiaoyao.li@intel.com>,
        Xu Yilun <yilun.xu@intel.com>,
        Chao Peng <chao.p.peng@linux.intel.com>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Anish Moorthy <amoorthy@google.com>,
        David Matlack <dmatlack@google.com>,
        Yu Zhang <yu.c.zhang@linux.intel.com>,
        Isaku Yamahata <isaku.yamahata@intel.com>,
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        Maciej Szmigiero <mail@maciej.szmigiero.name>,
        David Hildenbrand <david@redhat.com>,
        Quentin Perret <qperret@google.com>,
        Michael Roth <michael.roth@amd.com>,
        Wang <wei.w.wang@intel.com>,
        Liam Merwick <liam.merwick@oracle.com>,
        Isaku Yamahata <isaku.yamahata@gmail.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
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On Mon, Nov 6, 2023 at 4:04=E2=80=AFPM Sean Christopherson <seanjc@google.c=
om> wrote:
>
> On Mon, Nov 06, 2023, Fuad Tabba wrote:
> > On Sun, Nov 5, 2023 at 4:34=E2=80=AFPM Paolo Bonzini <pbonzini@redhat.c=
om> wrote:
> > >
> > > From: Sean Christopherson <seanjc@google.com>
> > >
> > > Add a "vm_shape" structure to encapsulate the selftests-defined "mode=
",
> > > along with the KVM-defined "type" for use when creating a new VM.  "m=
ode"
> > > tracks physical and virtual address properties, as well as the prefer=
red
> > > backing memory type, while "type" corresponds to the VM type.
> > >
> > > Taking the VM type will allow adding tests for KVM_CREATE_GUEST_MEMFD=
,
> > > a.k.a. guest private memory, without needing an entirely separate set=
 of
> > > helpers.  Guest private memory is effectively usable only by confiden=
tial
> > > VM types, and it's expected that x86 will double down and require uni=
que
> > > VM types for TDX and SNP guests.
> > >
> > > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > > Message-Id: <20231027182217.3615211-30-seanjc@google.com>
> > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > > ---
> >
> > nit: as in a prior selftest commit messages, references in the commit
> > message to guest _private_ memory. Should these be changed to just
> > guest memory?
>
> Hmm, no, "private" is mostly appropriate here.  At this point in time, on=
ly x86
> supports KVM_CREATE_GUEST_MEMFD, and x86 only supports it for private mem=
ory.
> And the purpose of letting x86 selftests specify KVM_X86_SW_PROTECTED_VM,=
 i.e.
> the reason this patch exists, is purely to get private memory.
>
> Maybe tweak the second paragraph to this?
>
> Taking the VM type will allow adding tests for KVM_CREATE_GUEST_MEMFD
> without needing an entirely separate set of helpers.  At this time,
> guest_memfd is effectively usable only by confidential VM types in the
> form of guest private memory, and it's expected that x86 will double down
> and require unique VM types for TDX and SNP guests.

sgtm
/fuad