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[2003:cb:c70f:8b00:ed48:6d18:2152:1cda]) by smtp.gmail.com with ESMTPSA id n9-20020a056000170900b0033d5fab6781sm12335002wrc.96.2024.02.22.08.28.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Feb 2024 08:28:38 -0800 (PST) Message-ID: <86461043-fa5b-405d-bd2e-dc1aba9977c5@redhat.com> Date: Thu, 22 Feb 2024 17:28:35 +0100 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 03/26] KVM: Add restricted support for mapping guestmem by the host To: Fuad Tabba , kvm@vger.kernel.org, kvmarm@lists.linux.dev 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 References: <20240222161047.402609-1-tabba@google.com> <20240222161047.402609-4-tabba@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit > +static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf) > +{ > + struct folio *folio; > + > + folio = kvm_gmem_get_folio(file_inode(vmf->vma->vm_file), vmf->pgoff); > + if (!folio) > + return VM_FAULT_SIGBUS; > + > + /* > + * Check if the page is allowed to be faulted to the host, with the > + * folio lock held to ensure that the check and incrementing the page > + * count are protected by the same folio lock. > + */ > + if (!kvm_gmem_isfaultable(vmf)) { > + folio_unlock(folio); > + return VM_FAULT_SIGBUS; > + } > + > + vmf->page = folio_file_page(folio, vmf->pgoff); We won't currently get hugetlb (or even THP) here. It mimics what shmem would do. finish_fault->set_pte_range() will call folio_add_file_rmap_ptes(), getting the rmap involved. Do we have some tests in place that make sure that fallocate(FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE) will properly unmap the page again (IOW, that the rmap does indeed work?). -- Cheers, David / dhildenb