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Mon, 5 Aug 2024 18:35:14 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Mon, 5 Aug 2024 11:35:13 -0700 From: Elliot Berman Date: Mon, 5 Aug 2024 11:34:47 -0700 Subject: [PATCH RFC 1/4] mm: Introduce guest_memfd Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <20240805-guest-memfd-lib-v1-1-e5a29a4ff5d7@quicinc.com> References: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> In-Reply-To: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> To: Andrew Morton , Paolo Bonzini , Sean Christopherson , Fuad Tabba , David Hildenbrand , Patrick Roy , , Ackerley Tng CC: , , , , , Elliot Berman X-Mailer: b4 0.13.0 X-ClientProxiedBy: nalasex01a.na.qualcomm.com (10.47.209.196) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: ZGxuxUGqCP_Vrg127mms6-uSzdAQx_Ti X-Proofpoint-GUID: ZGxuxUGqCP_Vrg127mms6-uSzdAQx_Ti X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-05_07,2024-08-02_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 bulkscore=0 suspectscore=0 adultscore=0 spamscore=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 mlxlogscore=902 phishscore=0 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408050133 In preparation for adding more features to KVM's guest_memfd, refactor and introduce a library which abstracts some of the core-mm decisions about managing folios associated with the file. The goal of the refactor serves two purposes: Provide an easier way to reason about memory in guest_memfd. With KVM supporting multiple confidentiality models (TDX, SEV-SNP, pKVM, ARM CCA), and coming support for allowing kernel and userspace to access this memory, it seems necessary to create a stronger abstraction between core-mm concerns and hypervisor concerns. Provide a common implementation for other hypervisors (Gunyah) to use. Signed-off-by: Elliot Berman --- include/linux/guest_memfd.h | 44 +++++++ mm/Kconfig | 3 + mm/Makefile | 1 + mm/guest_memfd.c | 285 ++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 333 insertions(+) diff --git a/include/linux/guest_memfd.h b/include/linux/guest_memfd.h new file mode 100644 index 000000000000..be56d9d53067 --- /dev/null +++ b/include/linux/guest_memfd.h @@ -0,0 +1,44 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved. + */ + +#ifndef _LINUX_GUEST_MEMFD_H +#define _LINUX_GUEST_MEMFD_H + +#include + +/** + * struct guest_memfd_operations - ops provided by owner to manage folios + * @invalidate_begin: called when folios should be unmapped from guest. + * May fail if folios couldn't be unmapped from guest. + * Required. + * @invalidate_end: called after invalidate_begin returns success. Optional. + * @prepare: called before a folio is mapped into the guest address space. + * Optional. + * @release: Called when releasing the guest_memfd file. Required. + */ +struct guest_memfd_operations { + int (*invalidate_begin)(struct inode *inode, pgoff_t offset, unsigned long nr); + void (*invalidate_end)(struct inode *inode, pgoff_t offset, unsigned long nr); + int (*prepare)(struct inode *inode, pgoff_t offset, struct folio *folio); + int (*release)(struct inode *inode); +}; + +/** + * @GUEST_MEMFD_GRAB_UPTODATE: Ensure pages are zeroed/up to date. + * If trusted hyp will do it, can ommit this flag + * @GUEST_MEMFD_PREPARE: Call the ->prepare() op, if present. + */ +enum { + GUEST_MEMFD_GRAB_UPTODATE = BIT(0), + GUEST_MEMFD_PREPARE = BIT(1), +}; + +struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags); +struct file *guest_memfd_alloc(const char *name, + const struct guest_memfd_operations *ops, + loff_t size, unsigned long flags); +bool is_guest_memfd(struct file *file, const struct guest_memfd_operations *ops); + +#endif diff --git a/mm/Kconfig b/mm/Kconfig index b72e7d040f78..333f46525695 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1168,6 +1168,9 @@ config SECRETMEM memory areas visible only in the context of the owning process and not mapped to other processes and other kernel page tables. +config GUEST_MEMFD + tristate + config ANON_VMA_NAME bool "Anonymous VMA name support" depends on PROC_FS && ADVISE_SYSCALLS && MMU diff --git a/mm/Makefile b/mm/Makefile index d2915f8c9dc0..e15a95ebeac5 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -122,6 +122,7 @@ obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o obj-$(CONFIG_PAGE_TABLE_CHECK) += page_table_check.o obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o obj-$(CONFIG_SECRETMEM) += secretmem.o +obj-$(CONFIG_GUEST_MEMFD) += guest_memfd.o obj-$(CONFIG_CMA_SYSFS) += cma_sysfs.o obj-$(CONFIG_USERFAULTFD) += userfaultfd.o obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o diff --git a/mm/guest_memfd.c b/mm/guest_memfd.c new file mode 100644 index 000000000000..580138b0f9d4 --- /dev/null +++ b/mm/guest_memfd.c @@ -0,0 +1,285 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved. + */ + +#include +#include +#include +#include + +struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags) +{ + struct inode *inode = file_inode(file); + struct guest_memfd_operations *ops = inode->i_private; + struct folio *folio; + int r; + + /* TODO: Support huge pages. */ + folio = filemap_grab_folio(inode->i_mapping, index); + if (IS_ERR(folio)) + return folio; + + /* + * Use the up-to-date flag to track whether or not the memory has been + * zeroed before being handed off to the guest. There is no backing + * storage for the memory, so the folio will remain up-to-date until + * it's removed. + */ + if ((flags & GUEST_MEMFD_GRAB_UPTODATE) && + !folio_test_uptodate(folio)) { + unsigned long nr_pages = folio_nr_pages(folio); + unsigned long i; + + for (i = 0; i < nr_pages; i++) + clear_highpage(folio_page(folio, i)); + + folio_mark_uptodate(folio); + } + + if (flags & GUEST_MEMFD_PREPARE && ops->prepare) { + r = ops->prepare(inode, index, folio); + if (r < 0) + goto out_err; + } + + /* + * Ignore accessed, referenced, and dirty flags. The memory is + * unevictable and there is no storage to write back to. + */ + return folio; +out_err: + folio_unlock(folio); + folio_put(folio); + return ERR_PTR(r); +} +EXPORT_SYMBOL_GPL(guest_memfd_grab_folio); + +static long gmem_punch_hole(struct file *file, loff_t offset, loff_t len) +{ + struct inode *inode = file_inode(file); + const struct guest_memfd_operations *ops = inode->i_private; + pgoff_t start = offset >> PAGE_SHIFT; + unsigned long nr = len >> PAGE_SHIFT; + long ret; + + /* + * Bindings must be stable across invalidation to ensure the start+end + * are balanced. + */ + filemap_invalidate_lock(inode->i_mapping); + + ret = ops->invalidate_begin(inode, start, nr); + if (ret) + goto out; + + truncate_inode_pages_range(inode->i_mapping, offset, offset + len - 1); + + if (ops->invalidate_end) + ops->invalidate_end(inode, start, nr); + +out: + filemap_invalidate_unlock(inode->i_mapping); + + return 0; +} + +static long gmem_allocate(struct file *file, loff_t offset, loff_t len) +{ + struct inode *inode = file_inode(file); + struct address_space *mapping = inode->i_mapping; + pgoff_t start, index, end; + int r; + + /* Dedicated guest is immutable by default. */ + if (offset + len > i_size_read(inode)) + return -EINVAL; + + filemap_invalidate_lock_shared(mapping); + + start = offset >> PAGE_SHIFT; + end = (offset + len) >> PAGE_SHIFT; + + r = 0; + for (index = start; index < end;) { + struct folio *folio; + + if (signal_pending(current)) { + r = -EINTR; + break; + } + + folio = guest_memfd_grab_folio(file, index, + GUEST_MEMFD_GRAB_UPTODATE | + GUEST_MEMFD_PREPARE); + if (!folio) { + r = -ENOMEM; + break; + } + + index = folio_next_index(folio); + + folio_unlock(folio); + folio_put(folio); + + /* 64-bit only, wrapping the index should be impossible. */ + if (WARN_ON_ONCE(!index)) + break; + + cond_resched(); + } + + filemap_invalidate_unlock_shared(mapping); + + return r; +} + +static long gmem_fallocate(struct file *file, int mode, loff_t offset, + loff_t len) +{ + int ret; + + if (!(mode & FALLOC_FL_KEEP_SIZE)) + return -EOPNOTSUPP; + + if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)) + return -EOPNOTSUPP; + + if (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len)) + return -EINVAL; + + if (mode & FALLOC_FL_PUNCH_HOLE) + ret = gmem_punch_hole(file, offset, len); + else + ret = gmem_allocate(file, offset, len); + + if (!ret) + file_modified(file); + return ret; +} + +static int gmem_release(struct inode *inode, struct file *file) +{ + struct guest_memfd_operations *ops = inode->i_private; + + return ops->release(inode); +} + +static struct file_operations gmem_fops = { + .open = generic_file_open, + .llseek = generic_file_llseek, + .release = gmem_release, + .fallocate = gmem_fallocate, + .owner = THIS_MODULE, +}; + +static int gmem_migrate_folio(struct address_space *mapping, struct folio *dst, + struct folio *src, enum migrate_mode mode) +{ + WARN_ON_ONCE(1); + return -EINVAL; +} + +static int gmem_error_folio(struct address_space *mapping, struct folio *folio) +{ + struct inode *inode = mapping->host; + struct guest_memfd_operations *ops = inode->i_private; + off_t offset = folio->index; + size_t nr = folio_nr_pages(folio); + int ret; + + filemap_invalidate_lock_shared(mapping); + + ret = ops->invalidate_begin(inode, offset, nr); + if (!ret && ops->invalidate_end) + ops->invalidate_end(inode, offset, nr); + + filemap_invalidate_unlock_shared(mapping); + + return ret; +} + +static bool gmem_release_folio(struct folio *folio, gfp_t gfp) +{ + struct inode *inode = folio_inode(folio); + struct guest_memfd_operations *ops = inode->i_private; + off_t offset = folio->index; + size_t nr = folio_nr_pages(folio); + int ret; + + ret = ops->invalidate_begin(inode, offset, nr); + if (ret) + return false; + if (ops->invalidate_end) + ops->invalidate_end(inode, offset, nr); + + return true; +} + +static const struct address_space_operations gmem_aops = { + .dirty_folio = noop_dirty_folio, + .migrate_folio = gmem_migrate_folio, + .error_remove_folio = gmem_error_folio, + .release_folio = gmem_release_folio, +}; + +static inline bool guest_memfd_check_ops(const struct guest_memfd_operations *ops) +{ + return ops->invalidate_begin && ops->release; +} + +struct file *guest_memfd_alloc(const char *name, + const struct guest_memfd_operations *ops, + loff_t size, unsigned long flags) +{ + struct inode *inode; + struct file *file; + + if (size <= 0 || !PAGE_ALIGNED(size)) + return ERR_PTR(-EINVAL); + + if (!guest_memfd_check_ops(ops)) + return ERR_PTR(-EINVAL); + + if (flags) + return ERR_PTR(-EINVAL); + + /* + * Use the so called "secure" variant, which creates a unique inode + * instead of reusing a single inode. Each guest_memfd instance needs + * its own inode to track the size, flags, etc. + */ + file = anon_inode_create_getfile(name, &gmem_fops, (void *)flags, + O_RDWR, NULL); + if (IS_ERR(file)) + return file; + + file->f_flags |= O_LARGEFILE; + + inode = file_inode(file); + WARN_ON(file->f_mapping != inode->i_mapping); + + inode->i_private = (void *)ops; /* discards const qualifier */ + inode->i_mapping->a_ops = &gmem_aops; + inode->i_mode |= S_IFREG; + inode->i_size = size; + mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); + mapping_set_inaccessible(inode->i_mapping); + /* Unmovable mappings are supposed to be marked unevictable as well. */ + WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); + + return file; +} +EXPORT_SYMBOL_GPL(guest_memfd_alloc); + +bool is_guest_memfd(struct file *file, const struct guest_memfd_operations *ops) +{ + if (file->f_op != &gmem_fops) + return false; + + struct inode *inode = file_inode(file); + struct guest_memfd_operations *gops = inode->i_private; 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Mon, 5 Aug 2024 18:35:14 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Mon, 5 Aug 2024 11:35:14 -0700 From: Elliot Berman Date: Mon, 5 Aug 2024 11:34:48 -0700 Subject: [PATCH RFC 2/4] kvm: Convert to use mm/guest_memfd Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <20240805-guest-memfd-lib-v1-2-e5a29a4ff5d7@quicinc.com> References: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> In-Reply-To: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> To: Andrew Morton , Paolo Bonzini , Sean Christopherson , Fuad Tabba , David Hildenbrand , Patrick Roy , , Ackerley Tng CC: , , , , , Elliot Berman X-Mailer: b4 0.13.0 X-ClientProxiedBy: nalasex01a.na.qualcomm.com (10.47.209.196) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: MTWcnK-X0sCx-AQ_MiaF48nCefXYbKNb X-Proofpoint-GUID: MTWcnK-X0sCx-AQ_MiaF48nCefXYbKNb X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-05_07,2024-08-02_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 priorityscore=1501 adultscore=0 mlxscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 mlxlogscore=999 clxscore=1011 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408050132 Use the recently created mm/guest_memfd implementation. No functional change intended. Signed-off-by: Elliot Berman --- virt/kvm/Kconfig | 1 + virt/kvm/guest_memfd.c | 299 ++++++++----------------------------------------- virt/kvm/kvm_main.c | 2 - virt/kvm/kvm_mm.h | 6 - 4 files changed, 49 insertions(+), 259 deletions(-) diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index b14e14cdbfb9..1147e004fcbd 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -106,6 +106,7 @@ config KVM_GENERIC_MEMORY_ATTRIBUTES config KVM_PRIVATE_MEM select XARRAY_MULTI + select GUEST_MEMFD bool config KVM_GENERIC_PRIVATE_MEM diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 1c509c351261..2fe3ff9e5793 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -1,9 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 -#include -#include +#include #include #include -#include #include "kvm_mm.h" @@ -13,9 +11,16 @@ struct kvm_gmem { struct list_head entry; }; -static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio) +static inline struct kvm_gmem *inode_to_kvm_gmem(struct inode *inode) { + struct list_head *gmem_list = &inode->i_mapping->i_private_list; + + return list_first_entry_or_null(gmem_list, struct kvm_gmem, entry); +} + #ifdef CONFIG_HAVE_KVM_GMEM_PREPARE +static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio) +{ struct list_head *gmem_list = &inode->i_mapping->i_private_list; struct kvm_gmem *gmem; @@ -45,57 +50,14 @@ static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct fol } } -#endif return 0; } +#endif -static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index, bool prepare) -{ - struct folio *folio; - - /* TODO: Support huge pages. */ - folio = filemap_grab_folio(inode->i_mapping, index); - if (IS_ERR(folio)) - return folio; - - /* - * Use the up-to-date flag to track whether or not the memory has been - * zeroed before being handed off to the guest. There is no backing - * storage for the memory, so the folio will remain up-to-date until - * it's removed. - * - * TODO: Skip clearing pages when trusted firmware will do it when - * assigning memory to the guest. - */ - if (!folio_test_uptodate(folio)) { - unsigned long nr_pages = folio_nr_pages(folio); - unsigned long i; - - for (i = 0; i < nr_pages; i++) - clear_highpage(folio_page(folio, i)); - - folio_mark_uptodate(folio); - } - - if (prepare) { - int r = kvm_gmem_prepare_folio(inode, index, folio); - if (r < 0) { - folio_unlock(folio); - folio_put(folio); - return ERR_PTR(r); - } - } - - /* - * Ignore accessed, referenced, and dirty flags. The memory is - * unevictable and there is no storage to write back to. - */ - return folio; -} - -static void kvm_gmem_invalidate_begin(struct kvm_gmem *gmem, pgoff_t start, +static int kvm_gmem_invalidate_begin(struct inode *inode, pgoff_t start, pgoff_t end) { + struct kvm_gmem *gmem = inode_to_kvm_gmem(inode); bool flush = false, found_memslot = false; struct kvm_memory_slot *slot; struct kvm *kvm = gmem->kvm; @@ -126,11 +88,14 @@ static void kvm_gmem_invalidate_begin(struct kvm_gmem *gmem, pgoff_t start, if (found_memslot) KVM_MMU_UNLOCK(kvm); + + return 0; } -static void kvm_gmem_invalidate_end(struct kvm_gmem *gmem, pgoff_t start, +static void kvm_gmem_invalidate_end(struct inode *inode, pgoff_t start, pgoff_t end) { + struct kvm_gmem *gmem = inode_to_kvm_gmem(inode); struct kvm *kvm = gmem->kvm; if (xa_find(&gmem->bindings, &start, end - 1, XA_PRESENT)) { @@ -140,106 +105,9 @@ static void kvm_gmem_invalidate_end(struct kvm_gmem *gmem, pgoff_t start, } } -static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len) -{ - struct list_head *gmem_list = &inode->i_mapping->i_private_list; - pgoff_t start = offset >> PAGE_SHIFT; - pgoff_t end = (offset + len) >> PAGE_SHIFT; - struct kvm_gmem *gmem; - - /* - * Bindings must be stable across invalidation to ensure the start+end - * are balanced. - */ - filemap_invalidate_lock(inode->i_mapping); - - list_for_each_entry(gmem, gmem_list, entry) - kvm_gmem_invalidate_begin(gmem, start, end); - - truncate_inode_pages_range(inode->i_mapping, offset, offset + len - 1); - - list_for_each_entry(gmem, gmem_list, entry) - kvm_gmem_invalidate_end(gmem, start, end); - - filemap_invalidate_unlock(inode->i_mapping); - - return 0; -} - -static long kvm_gmem_allocate(struct inode *inode, loff_t offset, loff_t len) +static int kvm_gmem_release(struct inode *inode) { - struct address_space *mapping = inode->i_mapping; - pgoff_t start, index, end; - int r; - - /* Dedicated guest is immutable by default. */ - if (offset + len > i_size_read(inode)) - return -EINVAL; - - filemap_invalidate_lock_shared(mapping); - - start = offset >> PAGE_SHIFT; - end = (offset + len) >> PAGE_SHIFT; - - r = 0; - for (index = start; index < end; ) { - struct folio *folio; - - if (signal_pending(current)) { - r = -EINTR; - break; - } - - folio = kvm_gmem_get_folio(inode, index, true); - if (IS_ERR(folio)) { - r = PTR_ERR(folio); - break; - } - - index = folio_next_index(folio); - - folio_unlock(folio); - folio_put(folio); - - /* 64-bit only, wrapping the index should be impossible. */ - if (WARN_ON_ONCE(!index)) - break; - - cond_resched(); - } - - filemap_invalidate_unlock_shared(mapping); - - return r; -} - -static long kvm_gmem_fallocate(struct file *file, int mode, loff_t offset, - loff_t len) -{ - int ret; - - if (!(mode & FALLOC_FL_KEEP_SIZE)) - return -EOPNOTSUPP; - - if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)) - return -EOPNOTSUPP; - - if (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len)) - return -EINVAL; - - if (mode & FALLOC_FL_PUNCH_HOLE) - ret = kvm_gmem_punch_hole(file_inode(file), offset, len); - else - ret = kvm_gmem_allocate(file_inode(file), offset, len); - - if (!ret) - file_modified(file); - return ret; -} - -static int kvm_gmem_release(struct inode *inode, struct file *file) -{ - struct kvm_gmem *gmem = file->private_data; + struct kvm_gmem *gmem = inode_to_kvm_gmem(inode); struct kvm_memory_slot *slot; struct kvm *kvm = gmem->kvm; unsigned long index; @@ -265,8 +133,8 @@ static int kvm_gmem_release(struct inode *inode, struct file *file) * Zap all SPTEs pointed at by this file. Do not free the backing * memory, as its lifetime is associated with the inode, not the file. */ - kvm_gmem_invalidate_begin(gmem, 0, -1ul); - kvm_gmem_invalidate_end(gmem, 0, -1ul); + kvm_gmem_invalidate_begin(inode, 0, -1ul); + kvm_gmem_invalidate_end(inode, 0, -1ul); list_del(&gmem->entry); @@ -293,56 +161,6 @@ static inline struct file *kvm_gmem_get_file(struct kvm_memory_slot *slot) return get_file_active(&slot->gmem.file); } -static struct file_operations kvm_gmem_fops = { - .open = generic_file_open, - .release = kvm_gmem_release, - .fallocate = kvm_gmem_fallocate, -}; - -void kvm_gmem_init(struct module *module) -{ - kvm_gmem_fops.owner = module; -} - -static int kvm_gmem_migrate_folio(struct address_space *mapping, - struct folio *dst, struct folio *src, - enum migrate_mode mode) -{ - WARN_ON_ONCE(1); - return -EINVAL; -} - -static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *folio) -{ - struct list_head *gmem_list = &mapping->i_private_list; - struct kvm_gmem *gmem; - pgoff_t start, end; - - filemap_invalidate_lock_shared(mapping); - - start = folio->index; - end = start + folio_nr_pages(folio); - - list_for_each_entry(gmem, gmem_list, entry) - kvm_gmem_invalidate_begin(gmem, start, end); - - /* - * Do not truncate the range, what action is taken in response to the - * error is userspace's decision (assuming the architecture supports - * gracefully handling memory errors). If/when the guest attempts to - * access a poisoned page, kvm_gmem_get_pfn() will return -EHWPOISON, - * at which point KVM can either terminate the VM or propagate the - * error to userspace. - */ - - list_for_each_entry(gmem, gmem_list, entry) - kvm_gmem_invalidate_end(gmem, start, end); - - filemap_invalidate_unlock_shared(mapping); - - return MF_DELAYED; -} - #ifdef CONFIG_HAVE_KVM_GMEM_INVALIDATE static void kvm_gmem_free_folio(struct folio *folio) { @@ -354,34 +172,25 @@ static void kvm_gmem_free_folio(struct folio *folio) } #endif -static const struct address_space_operations kvm_gmem_aops = { - .dirty_folio = noop_dirty_folio, - .migrate_folio = kvm_gmem_migrate_folio, - .error_remove_folio = kvm_gmem_error_folio, +static const struct guest_memfd_operations kvm_gmem_ops = { + .invalidate_begin = kvm_gmem_invalidate_begin, + .invalidate_end = kvm_gmem_invalidate_end, +#ifdef CONFIG_HAVE_KVM_GMEM_PREAPRE + .prepare = kvm_gmem_prepare_folio, +#endif #ifdef CONFIG_HAVE_KVM_GMEM_INVALIDATE .free_folio = kvm_gmem_free_folio, #endif + .release = kvm_gmem_release, }; -static int kvm_gmem_getattr(struct mnt_idmap *idmap, const struct path *path, - struct kstat *stat, u32 request_mask, - unsigned int query_flags) +static inline struct kvm_gmem *file_to_kvm_gmem(struct file *file) { - struct inode *inode = path->dentry->d_inode; - - generic_fillattr(idmap, request_mask, inode, stat); - return 0; -} + if (!is_guest_memfd(file, &kvm_gmem_ops)) + return NULL; -static int kvm_gmem_setattr(struct mnt_idmap *idmap, struct dentry *dentry, - struct iattr *attr) -{ - return -EINVAL; + return inode_to_kvm_gmem(file_inode(file)); } -static const struct inode_operations kvm_gmem_iops = { - .getattr = kvm_gmem_getattr, - .setattr = kvm_gmem_setattr, -}; static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) { @@ -401,31 +210,16 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) goto err_fd; } - file = anon_inode_create_getfile(anon_name, &kvm_gmem_fops, gmem, - O_RDWR, NULL); + file = guest_memfd_alloc(anon_name, &kvm_gmem_ops, size, 0); if (IS_ERR(file)) { err = PTR_ERR(file); goto err_gmem; } - file->f_flags |= O_LARGEFILE; - - inode = file->f_inode; - WARN_ON(file->f_mapping != inode->i_mapping); - - inode->i_private = (void *)(unsigned long)flags; - inode->i_op = &kvm_gmem_iops; - inode->i_mapping->a_ops = &kvm_gmem_aops; - inode->i_mode |= S_IFREG; - inode->i_size = size; - mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); - mapping_set_inaccessible(inode->i_mapping); - /* Unmovable mappings are supposed to be marked unevictable as well. */ - WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); - kvm_get_kvm(kvm); gmem->kvm = kvm; xa_init(&gmem->bindings); + inode = file_inode(file); list_add(&gmem->entry, &inode->i_mapping->i_private_list); fd_install(fd, file); @@ -469,11 +263,8 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, if (!file) return -EBADF; - if (file->f_op != &kvm_gmem_fops) - goto err; - - gmem = file->private_data; - if (gmem->kvm != kvm) + gmem = file_to_kvm_gmem(file); + if (!gmem || gmem->kvm != kvm) goto err; inode = file_inode(file); @@ -530,7 +321,9 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) if (!file) return; - gmem = file->private_data; + gmem = file_to_kvm_gmem(file); + if (!gmem) + return; filemap_invalidate_lock(file->f_mapping); xa_store_range(&gmem->bindings, start, end - 1, NULL, GFP_KERNEL); @@ -548,20 +341,24 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot, struct kvm_gmem *gmem = file->private_data; struct folio *folio; struct page *page; - int r; + int r, flags = GUEST_MEMFD_GRAB_UPTODATE; if (file != slot->gmem.file) { WARN_ON_ONCE(slot->gmem.file); return -EFAULT; } - gmem = file->private_data; - if (xa_load(&gmem->bindings, index) != slot) { - WARN_ON_ONCE(xa_load(&gmem->bindings, index)); + gmem = file_to_kvm_gmem(file); + if (WARN_ON_ONCE(!gmem)) + return -EINVAL; + + if (WARN_ON_ONCE(xa_load(&gmem->bindings, index) != slot)) return -EIO; - } - folio = kvm_gmem_get_folio(file_inode(file), index, prepare); + if (prepare) + flags |= GUEST_MEMFD_PREPARE; + + folio = guest_memfd_grab_folio(file, index, flags); if (IS_ERR(folio)) return PTR_ERR(folio); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index d0788d0a72cc..cad798f4e135 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -6516,8 +6516,6 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module) if (WARN_ON_ONCE(r)) goto err_vfio; - kvm_gmem_init(module); - /* * Registration _must_ be the very last thing done, as this exposes * /dev/kvm to userspace, i.e. all infrastructure must be setup! diff --git a/virt/kvm/kvm_mm.h b/virt/kvm/kvm_mm.h index 715f19669d01..6336a4fdcf50 100644 --- a/virt/kvm/kvm_mm.h +++ b/virt/kvm/kvm_mm.h @@ -36,17 +36,11 @@ static inline void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, #endif /* HAVE_KVM_PFNCACHE */ #ifdef CONFIG_KVM_PRIVATE_MEM -void kvm_gmem_init(struct module *module); int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args); int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned int fd, loff_t offset); 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Mon, 5 Aug 2024 18:35:14 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Mon, 5 Aug 2024 11:35:14 -0700 From: Elliot Berman Date: Mon, 5 Aug 2024 11:34:49 -0700 Subject: [PATCH RFC 3/4] mm: guest_memfd: Add option to remove guest private memory from direct map Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <20240805-guest-memfd-lib-v1-3-e5a29a4ff5d7@quicinc.com> References: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> In-Reply-To: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> To: Andrew Morton , Paolo Bonzini , Sean Christopherson , Fuad Tabba , David Hildenbrand , Patrick Roy , , Ackerley Tng CC: , , , , , Elliot Berman X-Mailer: b4 0.13.0 X-ClientProxiedBy: nalasex01a.na.qualcomm.com (10.47.209.196) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: Km60UcZQKmFHYOSjr87yEZONp7TaX5Yo X-Proofpoint-GUID: Km60UcZQKmFHYOSjr87yEZONp7TaX5Yo X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-05_07,2024-08-02_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 bulkscore=0 suspectscore=0 adultscore=0 spamscore=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 mlxlogscore=885 phishscore=0 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408050133 This patch was reworked from Patrick's patch: https://lore.kernel.org/all/20240709132041.3625501-6-roypat@amazon.co.uk/ While guest_memfd is not available to be mapped by userspace, it is still accessible through the kernel's direct map. This means that in scenarios where guest-private memory is not hardware protected, it can be speculatively read and its contents potentially leaked through hardware side-channels. Removing guest-private memory from the direct map, thus mitigates a large class of speculative execution issues [1, Table 1]. Direct map removal do not reuse the `.prepare` machinery, since `prepare` can be called multiple time, and it is the responsibility of the preparation routine to not "prepare" the same folio twice [2]. Thus, instead explicitly check if `filemap_grab_folio` allocated a new folio, and remove the returned folio from the direct map only if this was the case. The patch uses release_folio instead of free_folio to reinsert pages back into the direct map as by the time free_folio is called, folio->mapping can already be NULL. This means that a call to folio_inode inside free_folio might deference a NULL pointer, leaving no way to access the inode which stores the flags that allow determining whether the page was removed from the direct map in the first place. [1]: https://download.vusec.net/papers/quarantine_raid23.pdf Cc: Patrick Roy Signed-off-by: Elliot Berman --- include/linux/guest_memfd.h | 8 ++++++ mm/guest_memfd.c | 65 ++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 72 insertions(+), 1 deletion(-) diff --git a/include/linux/guest_memfd.h b/include/linux/guest_memfd.h index be56d9d53067..f9e4a27aed67 100644 --- a/include/linux/guest_memfd.h +++ b/include/linux/guest_memfd.h @@ -25,6 +25,14 @@ struct guest_memfd_operations { int (*release)(struct inode *inode); }; +/** + * @GUEST_MEMFD_FLAG_NO_DIRECT_MAP: When making folios inaccessible by host, also + * remove them from the kernel's direct map. + */ +enum { + GUEST_MEMFD_FLAG_NO_DIRECT_MAP = BIT(0), +}; + /** * @GUEST_MEMFD_GRAB_UPTODATE: Ensure pages are zeroed/up to date. * If trusted hyp will do it, can ommit this flag diff --git a/mm/guest_memfd.c b/mm/guest_memfd.c index 580138b0f9d4..e9d8cab72b28 100644 --- a/mm/guest_memfd.c +++ b/mm/guest_memfd.c @@ -7,9 +7,55 @@ #include #include #include +#include + +static inline int guest_memfd_folio_private(struct folio *folio) +{ + unsigned long nr_pages = folio_nr_pages(folio); + unsigned long i; + int r; + + for (i = 0; i < nr_pages; i++) { + struct page *page = folio_page(folio, i); + + r = set_direct_map_invalid_noflush(page); + if (r < 0) + goto out_remap; + } + + folio_set_private(folio); + return 0; +out_remap: + for (; i > 0; i--) { + struct page *page = folio_page(folio, i - 1); + + BUG_ON(set_direct_map_default_noflush(page)); + } + return r; +} + +static inline void guest_memfd_folio_clear_private(struct folio *folio) +{ + unsigned long start = (unsigned long)folio_address(folio); + unsigned long nr = folio_nr_pages(folio); + unsigned long i; + + if (!folio_test_private(folio)) + return; + + for (i = 0; i < nr; i++) { + struct page *page = folio_page(folio, i); + + BUG_ON(set_direct_map_default_noflush(page)); + } + flush_tlb_kernel_range(start, start + folio_size(folio)); + + folio_clear_private(folio); +} struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags) { + unsigned long gmem_flags = (unsigned long)file->private_data; struct inode *inode = file_inode(file); struct guest_memfd_operations *ops = inode->i_private; struct folio *folio; @@ -43,6 +89,12 @@ struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags goto out_err; } + if (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP) { + r = guest_memfd_folio_private(folio); + if (r) + goto out_err; + } + /* * Ignore accessed, referenced, and dirty flags. The memory is * unevictable and there is no storage to write back to. @@ -213,14 +265,25 @@ static bool gmem_release_folio(struct folio *folio, gfp_t gfp) if (ops->invalidate_end) ops->invalidate_end(inode, offset, nr); + guest_memfd_folio_clear_private(folio); + return true; } +static void gmem_invalidate_folio(struct folio *folio, size_t offset, size_t len) +{ + /* not yet supported */ + BUG_ON(offset || len != folio_size(folio)); + + BUG_ON(!gmem_release_folio(folio, 0)); +} + static const struct address_space_operations gmem_aops = { .dirty_folio = noop_dirty_folio, .migrate_folio = gmem_migrate_folio, .error_remove_folio = gmem_error_folio, .release_folio = gmem_release_folio, + .invalidate_folio = gmem_invalidate_folio, }; static inline bool guest_memfd_check_ops(const struct guest_memfd_operations *ops) @@ -241,7 +304,7 @@ struct file *guest_memfd_alloc(const char *name, if (!guest_memfd_check_ops(ops)) return ERR_PTR(-EINVAL); - if (flags) + if (flags & ~GUEST_MEMFD_FLAG_NO_DIRECT_MAP) return ERR_PTR(-EINVAL); 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Mon, 5 Aug 2024 18:35:15 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Mon, 5 Aug 2024 11:35:14 -0700 From: Elliot Berman Date: Mon, 5 Aug 2024 11:34:50 -0700 Subject: [PATCH RFC 4/4] mm: guest_memfd: Add ability for mmap'ing pages Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <20240805-guest-memfd-lib-v1-4-e5a29a4ff5d7@quicinc.com> References: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> In-Reply-To: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> To: Andrew Morton , Paolo Bonzini , Sean Christopherson , Fuad Tabba , David Hildenbrand , Patrick Roy , , Ackerley Tng CC: , , , , , Elliot Berman X-Mailer: b4 0.13.0 X-ClientProxiedBy: nalasex01a.na.qualcomm.com (10.47.209.196) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: sfX1xQ5G9G6F0uigExaJMuPsByDlTZno X-Proofpoint-GUID: sfX1xQ5G9G6F0uigExaJMuPsByDlTZno X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-05_07,2024-08-02_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 spamscore=0 mlxlogscore=999 phishscore=0 clxscore=1015 suspectscore=0 adultscore=0 mlxscore=0 malwarescore=0 bulkscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408050132 Confidential/protected guest virtual machines want to share some memory back with the host Linux. For example, virtqueues allow host and protected guest to exchange data. In MMU-only isolation of protected guest virtual machines, the transition between "shared" and "private" can be done in-place without a trusted hypervisor copying pages. Add support for this feature and allow Linux to mmap host-accessible pages. When the owner provides an ->accessible() callback in the struct guest_memfd_operations, guest_memfd allows folios to be mapped when the ->accessible() callback returns 0. To safely make inaccessible: ``` folio = guest_memfd_grab_folio(inode, index, flags); r = guest_memfd_make_inaccessible(inode, folio); if (r) goto err; hypervisor_does_guest_mapping(folio); folio_unlock(folio); ``` hypervisor_does_s2_mapping(folio) should make it so ops->accessible(...) on those folios fails. The folio lock ensures atomicity. Signed-off-by: Elliot Berman --- include/linux/guest_memfd.h | 7 ++++ mm/guest_memfd.c | 81 ++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 87 insertions(+), 1 deletion(-) diff --git a/include/linux/guest_memfd.h b/include/linux/guest_memfd.h index f9e4a27aed67..edcb4ba60cb0 100644 --- a/include/linux/guest_memfd.h +++ b/include/linux/guest_memfd.h @@ -16,12 +16,18 @@ * @invalidate_end: called after invalidate_begin returns success. Optional. * @prepare: called before a folio is mapped into the guest address space. * Optional. + * @accessible: called after prepare returns success and before it's mapped + * into the guest address space. Returns 0 if the folio can be + * accessed. + * Optional. If not present, assumes folios are never accessible. * @release: Called when releasing the guest_memfd file. Required. */ struct guest_memfd_operations { int (*invalidate_begin)(struct inode *inode, pgoff_t offset, unsigned long nr); void (*invalidate_end)(struct inode *inode, pgoff_t offset, unsigned long nr); int (*prepare)(struct inode *inode, pgoff_t offset, struct folio *folio); + int (*accessible)(struct inode *inode, struct folio *folio, + pgoff_t offset, unsigned long nr); int (*release)(struct inode *inode); }; @@ -48,5 +54,6 @@ struct file *guest_memfd_alloc(const char *name, const struct guest_memfd_operations *ops, loff_t size, unsigned long flags); bool is_guest_memfd(struct file *file, const struct guest_memfd_operations *ops); +int guest_memfd_make_inaccessible(struct file *file, struct folio *folio); #endif diff --git a/mm/guest_memfd.c b/mm/guest_memfd.c index e9d8cab72b28..6b5609932ca5 100644 --- a/mm/guest_memfd.c +++ b/mm/guest_memfd.c @@ -9,6 +9,8 @@ #include #include +#include "internal.h" + static inline int guest_memfd_folio_private(struct folio *folio) { unsigned long nr_pages = folio_nr_pages(folio); @@ -89,7 +91,7 @@ struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags goto out_err; } - if (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP) { + if (!ops->accessible && (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP)) { r = guest_memfd_folio_private(folio); if (r) goto out_err; @@ -107,6 +109,82 @@ struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags } EXPORT_SYMBOL_GPL(guest_memfd_grab_folio); +int guest_memfd_make_inaccessible(struct file *file, struct folio *folio) +{ + unsigned long gmem_flags = (unsigned long)file->private_data; + unsigned long i; + int r; + + unmap_mapping_folio(folio); + + /** + * We can't use the refcount. It might be elevated due to + * guest/vcpu trying to access same folio as another vcpu + * or because userspace is trying to access folio for same reason + * + * folio_lock serializes the transitions between (in)accessible + */ + if (folio_maybe_dma_pinned(folio)) + return -EBUSY; + + if (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP) { + r = guest_memfd_folio_private(folio); + if (r) + return r; + } + + return 0; +} + +static vm_fault_t gmem_fault(struct vm_fault *vmf) +{ + struct file *file = vmf->vma->vm_file; + struct inode *inode = file_inode(file); + const struct guest_memfd_operations *ops = inode->i_private; + struct folio *folio; + pgoff_t off; + int r; + + folio = guest_memfd_grab_folio(file, vmf->pgoff, GUEST_MEMFD_GRAB_UPTODATE); + if (!folio) + return VM_FAULT_SIGBUS; + + off = vmf->pgoff & (folio_nr_pages(folio) - 1); + r = ops->accessible(inode, folio, off, 1); + if (r) { + folio_unlock(folio); + folio_put(folio); + return VM_FAULT_SIGBUS; + } + + guest_memfd_folio_clear_private(folio); + + vmf->page = folio_page(folio, off); + + return VM_FAULT_LOCKED; +} + +static const struct vm_operations_struct gmem_vm_ops = { + .fault = gmem_fault, +}; + +static int gmem_mmap(struct file *file, struct vm_area_struct *vma) +{ + const struct guest_memfd_operations *ops = file_inode(file)->i_private; + + if (!ops->accessible) + return -EPERM; + + /* No support for private mappings to avoid COW. */ + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) != + (VM_SHARED | VM_MAYSHARE)) + return -EINVAL; + + file_accessed(file); + vma->vm_ops = &gmem_vm_ops; + return 0; +} + static long gmem_punch_hole(struct file *file, loff_t offset, loff_t len) { struct inode *inode = file_inode(file); @@ -220,6 +298,7 @@ static int gmem_release(struct inode *inode, struct file *file) static struct file_operations gmem_fops = { .open = generic_file_open, .llseek = generic_file_llseek, + .mmap = gmem_mmap, .release = gmem_release, .fallocate = gmem_fallocate, .owner = THIS_MODULE,