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[2003:cb:c70b:db00:724d:8b0c:110e:3713]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438b31b1566sm28584345e9.24.2025.01.22.07.41.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Jan 2025 07:41:52 -0800 (PST) Message-ID: <03bbcd00-bd5e-47de-8b20-31636e361f52@redhat.com> Date: Wed, 22 Jan 2025 16:41:49 +0100 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 0/9] KVM: Mapping of guest_memfd at the host and a software protected VM type From: David Hildenbrand To: Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: 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, 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, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com References: <20250122152738.1173160-1-tabba@google.com> Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 22.01.25 16:35, David Hildenbrand wrote: > On 22.01.25 16:27, Fuad Tabba wrote: >> The purpose of this series is to serve as a potential base for >> restricted mmap() support for guest_memfd [1]. It would allow >> experimentation with what that support would be like, in the safe >> environment of a new VM type used for testing. >> >> This series adds a new VM type for arm64, >> KVM_VM_TYPE_ARM_SW_PROTECTED, analogous to the x86 >> KVM_X86_SW_PROTECTED_VM. This type is to serve as a development >> and testing vehicle for Confidential (CoCo) VMs. >> >> Similar to the x86 type, this is currently only for development >> and testing. It's not meant to be used for "real" VMs, and >> especially not in production. The behavior and effective ABI for >> software-protected VMs is unstable. >> >> This series enables mmap() support for guest_memfd specifically >> for the new software-protected VM type, only when explicitly >> enabled in the config. > > Hi! > > IIUC, in this series, there is no "private" vs "shared" distinction, > right? So all pages are mappable, and "conversion" does not exist? Ah, I spot: +#define kvm_arch_private_mem_inplace(kvm) \ + (IS_ENABLED(CONFIG_KVM_GMEM_MAPPABLE) && \ + ((kvm)->arch.vm_type & KVM_VM_TYPE_ARM_SW_PROTECTED)) Which makes me wonder, why don't we need the same way of making sure all references/mappings are gone (+ new page type) when doing the shared -> private conversion? Or is this somewhere in here where I didn't spot it yet? -- Cheers, David / dhildenb