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AJvYcCXkMR+4gpmQBlsUS2KT15+xsXu+IJ7XXn+FR9ZXr2uR/EzBszyHJt8FpL2i7g5N14/RXlGKeVeL/A==@kvack.org X-Gm-Message-State: AOJu0YyFk/Wwh7yhOMPrzJGbYZVaAF+Rp6GC7ke6DtTKQzX7DL6+uZRq 1eXR9OXzMXogqZL/itMbiA+/jVXhNoWR4JNWa1u8Gr9lXNcbM2LHpIDHn4/zzydWbgxcpggNPw= = X-Google-Smtp-Source: AGHT+IEk7whKV8qDP3YJYflDIlm8Cb6VQQ/o4v2sTpWwI0tdVBtFPk7h94MV+FENYUw5CL+bP9BAxRH9cQ== X-Received: from wmqe5.prod.google.com ([2002:a05:600c:4e45:b0:439:8333:1efb]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:1d1e:b0:439:6118:c188 with SMTP id 5b1f17b1804b1-43999dd1dc6mr3930085e9.19.1739899508877; Tue, 18 Feb 2025 09:25:08 -0800 (PST) Date: Tue, 18 Feb 2025 17:24:53 +0000 In-Reply-To: <20250218172500.807733-1-tabba@google.com> Mime-Version: 1.0 References: <20250218172500.807733-1-tabba@google.com> X-Mailer: git-send-email 2.48.1.601.g30ceb7b040-goog Message-ID: <20250218172500.807733-4-tabba@google.com> Subject: [PATCH v4 03/10] KVM: guest_memfd: Allow host to map guest_memfd() pages From: Fuad Tabba To: 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, 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, 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, tabba@google.com X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 418CEA000D X-Stat-Signature: ijz556omy8i91noiq8tgnkdpyi4awwjt X-HE-Tag: 1739899510-285682 X-HE-Meta: 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 AhxAK4FU 8RTGkOQDI7VIWLo4GHRH9oZwHVQtGtTUaAvblcZAHxCY2LXLeqqQNMxzyzSV5TCica32lpOKtw6ZgtGUfF1ZnG5sww8R/B6QP507Q8cTRREP+RsUHkIlqP4KrZp8MTzAytxMcX34cGLeMs9J1Z3L63O+5E04G18QfcvGySm4QNaDFE8FxA6ksRGm+6TJ8lM6He3+tBFRfbpjC1jcLGoxI0NLPRnSkjQQ1N8/SrHLSv9Iw7yvp85qe9tWrX5H9NCqC/8RF7tW3DXz1gRxhZvixkJtsMlKTComqyX7AnFYzoe9RUR2NJrzULSZSHB03kgA5U4sHCN49Ty8sg3uB0Wnp6acXZl+c6I5pwqGNnuIHZ5QEu4Fdr85tCHFb3B0gFypJJIGyr7+Jt1WxzpQgwHKGNG1FKJv+S/9O+4uJ00IfuCGuuR9nBzdSXJeVXxEhvuDDAAdLrXP5DMx0EurXFDRzjI3NoW3R/7bM7RrWa+UX8r3fbgGwaFogSLI6R/k1eEUPJFjdhaGXfTYHCstQcOqyNOlOmsgysEboOhj4EmhdATY6dsbyzzWY03VRzyKqIJwtd/vRETakJKwKQ2936Bt9RZXvc/AgoO+8TBSadZ3i4eZcaSN5+au0XovidMY0IDit0u6cyofCGOp0C//Ja9M+SiqagA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Add support for mmap() and fault() for guest_memfd backed memory in the host for VMs that support in-place conversion between shared and private. To that end, this patch adds the ability to check whether the VM type supports in-place conversion, and only allows mapping its memory if that's the case. This behavior is also gated by the configuration option KVM_GMEM_SHARED_MEM. Signed-off-by: Fuad Tabba --- include/linux/kvm_host.h | 11 +++++ virt/kvm/guest_memfd.c | 103 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 114 insertions(+) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 3ad0719bfc4f..f9e8b10a4b09 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -728,6 +728,17 @@ static inline bool kvm_arch_has_private_mem(struct kvm *kvm) } #endif +/* + * Arch code must define kvm_arch_gmem_supports_shared_mem if support for + * private memory is enabled and it supports in-place shared/private conversion. + */ +#if !defined(kvm_arch_gmem_supports_shared_mem) && !IS_ENABLED(CONFIG_KVM_PRIVATE_MEM) +static inline bool kvm_arch_gmem_supports_shared_mem(struct kvm *kvm) +{ + return false; +} +#endif + #ifndef kvm_arch_has_readonly_mem static inline bool kvm_arch_has_readonly_mem(struct kvm *kvm) { diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index c6f6792bec2a..30b47ff0e6d2 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -317,9 +317,112 @@ void kvm_gmem_handle_folio_put(struct folio *folio) { WARN_ONCE(1, "A placeholder that shouldn't trigger. Work in progress."); } + +static bool kvm_gmem_offset_is_shared(struct file *file, pgoff_t index) +{ + struct kvm_gmem *gmem = file->private_data; + + /* For now, VMs that support shared memory share all their memory. */ + return kvm_arch_gmem_supports_shared_mem(gmem->kvm); +} + +static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf) +{ + struct inode *inode = file_inode(vmf->vma->vm_file); + struct folio *folio; + vm_fault_t ret = VM_FAULT_LOCKED; + + filemap_invalidate_lock_shared(inode->i_mapping); + + folio = kvm_gmem_get_folio(inode, vmf->pgoff); + if (IS_ERR(folio)) { + switch (PTR_ERR(folio)) { + case -EAGAIN: + ret = VM_FAULT_RETRY; + break; + case -ENOMEM: + ret = VM_FAULT_OOM; + break; + default: + ret = VM_FAULT_SIGBUS; + break; + } + goto out_filemap; + } + + if (folio_test_hwpoison(folio)) { + ret = VM_FAULT_HWPOISON; + goto out_folio; + } + + /* Must be called with folio lock held, i.e., after kvm_gmem_get_folio() */ + if (!kvm_gmem_offset_is_shared(vmf->vma->vm_file, vmf->pgoff)) { + ret = VM_FAULT_SIGBUS; + goto out_folio; + } + + /* + * Only private folios are marked as "guestmem" so far, and we never + * expect private folios at this point. + */ + if (WARN_ON_ONCE(folio_test_guestmem(folio))) { + ret = VM_FAULT_SIGBUS; + goto out_folio; + } + + /* No support for huge pages. */ + if (WARN_ON_ONCE(folio_test_large(folio))) { + ret = VM_FAULT_SIGBUS; + goto out_folio; + } + + if (!folio_test_uptodate(folio)) { + clear_highpage(folio_page(folio, 0)); + kvm_gmem_mark_prepared(folio); + } + + vmf->page = folio_file_page(folio, vmf->pgoff); + +out_folio: + if (ret != VM_FAULT_LOCKED) { + folio_unlock(folio); + folio_put(folio); + } + +out_filemap: + filemap_invalidate_unlock_shared(inode->i_mapping); + + return ret; +} + +static const struct vm_operations_struct kvm_gmem_vm_ops = { + .fault = kvm_gmem_fault, +}; + +static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct kvm_gmem *gmem = file->private_data; + + if (!kvm_arch_gmem_supports_shared_mem(gmem->kvm)) + return -ENODEV; + + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) != + (VM_SHARED | VM_MAYSHARE)) { + return -EINVAL; + } + + file_accessed(file); + vm_flags_set(vma, VM_DONTDUMP); + vma->vm_ops = &kvm_gmem_vm_ops; + + return 0; +} +#else +#define kvm_gmem_mmap NULL #endif /* CONFIG_KVM_GMEM_SHARED_MEM */ static struct file_operations kvm_gmem_fops = { + .mmap = kvm_gmem_mmap, .open = generic_file_open, .release = kvm_gmem_release, .fallocate = kvm_gmem_fallocate,