linux-kernel - Re: [PATCH 27/34] KVM: selftests: Introduce VM "shape" to allow tests to specify the VM type

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Message-ID: <CA+EHjTzc4zwN1atU1mSnbi3Lvb0c83MATQSk1uSWxae2iKi0aw@mail.gmail.com>
Date:   Mon, 6 Nov 2023 16:17:09 +0000
From:   Fuad Tabba <tabba@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Anish Moorthy <amoorthy@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH 27/34] KVM: selftests: Introduce VM "shape" to allow tests
 to specify the VM type

On Mon, Nov 6, 2023 at 4:04 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Mon, Nov 06, 2023, Fuad Tabba wrote:
> > On Sun, Nov 5, 2023 at 4:34 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
> > >
> > > From: Sean Christopherson <seanjc@...gle.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.  "mode"
> > > tracks physical and virtual address properties, as well as the preferred
> > > 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 confidential
> > > VM types, and it's expected that x86 will double down and require unique
> > > VM types for TDX and SNP guests.
> > >
> > > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > > Message-Id: <20231027182217.3615211-30-seanjc@...gle.com>
> > > Signed-off-by: Paolo Bonzini <pbonzini@...hat.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, only x86
> supports KVM_CREATE_GUEST_MEMFD, and x86 only supports it for private memory.
> 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