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[34.91.112.229]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5dece1d3738sm2872600a12.46.2025.02.14.03.13.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Feb 2025 03:13:46 -0800 (PST) Date: Fri, 14 Feb 2025 11:13:41 +0000 From: Quentin Perret To: Patrick Roy Cc: Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, yu.c.zhang@linux.intel.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, keirf@google.com, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com Subject: Re: [PATCH v3 09/11] KVM: arm64: Introduce KVM_VM_TYPE_ARM_SW_PROTECTED machine type Message-ID: References: <20250211121128.703390-1-tabba@google.com> <20250211121128.703390-10-tabba@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 838EF180002 X-Rspamd-Server: rspam12 X-Stat-Signature: zjo63aprkuuy3orp88f14wzapf5357ua X-HE-Tag: 1739531629-53532 X-HE-Meta: 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 x+Avdlx8 yzvOZBSChZEc7ccF85rj8d27ZMNHfbNWdXAncrDrecog4a17RxtMzNRxUWK3hwM9wANH27V9UOkpV+ebLhjanY98xfkz/HiA9CCwdkm5yF0jJn/5XPX2Y6qn6NvzxqZ0jEXwfhhSq3piT9zZJne1pL5dgJukut2G/qrr8ECn8Bmjw+hD7mpzMhsN8Rq6e+dsesZFl+CPQEJB93QVJ/e/KsVYmApM2l3/FwFtTaeY6vEy9p4JvFPqDAySo0tgNwSHOJ77xaZA+LZYqe3tvp4yXPOGJ87YZd+cBMhv0k1W7EApz7KUbJQRkW0vIgDOEiDgD0q/fb7TaWNUmhV/RbfcBcQiIY5uOBa7RgaUzhGz+i6qX8G3HvTuxFodzWaN7km9corjc60jMdD73QVnJG2ZhQktRom2lkrrAjNvA4T2fW4ihxFr2yhyNebZj5uqKMuwThlzDMB/+ZYhAMpJVRoErErETjBHzCzi19oy+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.013554, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tuesday 11 Feb 2025 at 17:09:20 (+0000), Quentin Perret wrote: > Hi Patrick, > > On Tuesday 11 Feb 2025 at 16:32:31 (+0000), Patrick Roy wrote: > > I was hoping that SW_PROTECTED_VM will be the VM type that something > > like Firecracker could use, e.g. an interface to guest_memfd specifically > > _without_ pKVM, as Fuad was saying. > > I had, probably incorrectly, assumed that we'd eventually want to allow > gmem for all VMs, including traditional KVM VMs that don't have anything > special. Perhaps the gmem support could be exposed via a KVM_CAP in this > case? > > Anyway, no objection to the proposed approach in this patch assuming we > will eventually have HW_PROTECTED_VM for pKVM VMs, and that _that_ can be > bit 31 :). Thinking about this a bit deeper, I am still wondering what this new SW_PROTECTED VM type is buying us? Given that SW_PROTECTED VMs accept both guest-memfd backed memslots and traditional HVA-backed memslots, we could just make normal KVM guests accept guest-memfd memslots and get the same thing? Is there any reason not to do that instead? Even though SW_PROTECTED VMs are documented as 'unstable', the reality is this is UAPI and you can bet it will end up being relied upon, so I would prefer to have a solid reason for introducing this new VM type. Cheers, Quentin