On 01.12.2020 15:24, Dr. David Alan Gilbert wrote:
* Andrey Gruzdev (andrey.gruz...@virtuozzo.com) wrote:Implemented support for the whole RAM block memory protection/un-protection. Introduced higher level ram_write_tracking_start() and ram_write_tracking_stop() to start/stop tracking guest memory writes.Signed-off-by: Andrey Gruzdev <andrey.gruz...@virtuozzo.com> --- include/exec/memory.h | 7 ++ include/qemu/userfaultfd.h | 29 +++++ migration/ram.c | 120 +++++++++++++++++++++ migration/ram.h | 4 + util/meson.build | 1 + util/userfaultfd.c | 215 +++++++++++++++++++++++++++++++++++++ 6 files changed, 376 insertions(+) create mode 100644 include/qemu/userfaultfd.h create mode 100644 util/userfaultfd.c diff --git a/include/exec/memory.h b/include/exec/memory.h index 0f3e6bcd5e..3d798fce16 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -139,6 +139,13 @@ typedef struct IOMMUNotifier IOMMUNotifier; /* RAM is a persistent kind memory */ #define RAM_PMEM (1 << 5)+/*+ * UFFDIO_WRITEPROTECT is used on this RAMBlock to + * support 'write-tracking' migration type. + * Implies ram_state->ram_wt_enabled. + */ +#define RAM_UF_WRITEPROTECT (1 << 6) + static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, IOMMUNotifierFlag flags, hwaddr start, hwaddr end, diff --git a/include/qemu/userfaultfd.h b/include/qemu/userfaultfd.h new file mode 100644 index 0000000000..fb843c76db --- /dev/null +++ b/include/qemu/userfaultfd.h @@ -0,0 +1,29 @@ +/* + * Linux UFFD-WP support + * + * Copyright Virtuozzo GmbH, 2020 + * + * Authors: + * Andrey Gruzdev <andrey.gruz...@virtuozzo.com> + * + * This work is licensed under the terms of the GNU GPL, version 2 or + * later. See the COPYING file in the top-level directory. + */ + +#ifndef USERFAULTFD_H +#define USERFAULTFD_H + +#include "qemu/osdep.h" +#include "exec/hwaddr.h" +#include <linux/userfaultfd.h> + +int uffd_create_fd(void); +void uffd_close_fd(int uffd); +int uffd_register_memory(int uffd, hwaddr start, hwaddr length, + bool track_missing, bool track_wp); +int uffd_unregister_memory(int uffd, hwaddr start, hwaddr length); +int uffd_protect_memory(int uffd, hwaddr start, hwaddr length, bool wp); +int uffd_read_events(int uffd, struct uffd_msg *msgs, int count); +bool uffd_poll_events(int uffd, int tmo); + +#endif /* USERFAULTFD_H */ diff --git a/migration/ram.c b/migration/ram.c index 7811cde643..3adfd1948d 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -56,6 +56,11 @@ #include "savevm.h" #include "qemu/iov.h" #include "multifd.h" +#include "sysemu/runstate.h" + +#ifdef CONFIG_LINUX +#include "qemu/userfaultfd.h" +#endif/***********************************************************//* ram save/restore */ @@ -298,6 +303,8 @@ struct RAMSrcPageRequest { struct RAMState { /* QEMUFile used for this migration */ QEMUFile *f; + /* UFFD file descriptor, used in 'write-tracking' migration */ + int uffdio_fd; /* Last block that we have visited searching for dirty pages */ RAMBlock *last_seen_block; /* Last block from where we have sent data */ @@ -3788,6 +3795,119 @@ static int ram_resume_prepare(MigrationState *s, void *opaque) return 0; }+/*+ * ram_write_tracking_start: start UFFD-WP memory tracking + * + * Returns 0 for success or negative value in case of error + * + */ +int ram_write_tracking_start(void)Please split this stuff off into a separate patch; just make this one the userfaultfd.[ch] and then a separate one for gluing it into ram.c
Yep, I'm separating it now - userfaultdf.c and ram_write_tracking stuff, they go to different patches.
+{ +#ifdef CONFIG_LINUX + int uffd; + RAMState *rs = ram_state; + RAMBlock *bs; + + /* Open UFFD file descriptor */ + uffd = uffd_create_fd(); + if (uffd < 0) { + return uffd; + } + rs->uffdio_fd = uffd; + + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + /* Nothing to do with read-only and MMIO-writable regions */ + if (bs->mr->readonly || bs->mr->rom_device) { + continue; + } + + bs->flags |= RAM_UF_WRITEPROTECT; + /* Register block memory with UFFD to track writes */ + if (uffd_register_memory(rs->uffdio_fd, (hwaddr) bs->host, + bs->max_length, false, true)) { + goto fail; + } + /* Apply UFFD write protection to the block memory range */ + if (uffd_protect_memory(rs->uffdio_fd, (hwaddr) bs->host, + bs->max_length, true)) { + goto fail; + } + + info_report("UFFD-WP write-tracking enabled: " + "block_id=%s page_size=%zu start=%p length=%lu " + "romd_mode=%i ram=%i readonly=%i nonvolatile=%i rom_device=%i", + bs->idstr, bs->page_size, bs->host, bs->max_length, + bs->mr->romd_mode, bs->mr->ram, bs->mr->readonly, + bs->mr->nonvolatile, bs->mr->rom_device); + } + + return 0; + +fail: + error_report("ram_write_tracking_start() failed: restoring initial memory state"); + + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + if ((bs->flags & RAM_UF_WRITEPROTECT) == 0) { + continue; + } + /* + * In case some memory block failed to be write-protected + * remove protection and unregister all succeeded RAM blocks + */ + uffd_protect_memory(rs->uffdio_fd, (hwaddr) bs->host, bs->max_length, false); + uffd_unregister_memory(rs->uffdio_fd, (hwaddr) bs->host, bs->max_length); + /* Cleanup flags */ + bs->flags &= ~RAM_UF_WRITEPROTECT; + } + + uffd_close_fd(uffd); + rs->uffdio_fd = -1; + return -1; +#else + rs->uffdio_fd = -1; + error_setg(&migrate_get_current()->error, + "Background-snapshot not supported on non-Linux hosts"); + return -1; +#endif /* CONFIG_LINUX */ +} + +/** + * ram_write_tracking_stop: stop UFFD-WP memory tracking and remove protection + */ +void ram_write_tracking_stop(void) +{ +#ifdef CONFIG_LINUX + RAMState *rs = ram_state; + RAMBlock *bs; + assert(rs->uffdio_fd >= 0); + + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + if ((bs->flags & RAM_UF_WRITEPROTECT) == 0) { + continue; + } + /* Remove protection and unregister all affected RAM blocks */ + uffd_protect_memory(rs->uffdio_fd, (hwaddr) bs->host, bs->max_length, false); + uffd_unregister_memory(rs->uffdio_fd, (hwaddr) bs->host, bs->max_length); + /* Cleanup flags */ + bs->flags &= ~RAM_UF_WRITEPROTECT; + + info_report("UFFD-WP write-tracking disabled: " + "block_id=%s page_size=%zu start=%p length=%lu " + "romd_mode=%i ram=%i readonly=%i nonvolatile=%i rom_device=%i", + bs->idstr, bs->page_size, bs->host, bs->max_length, + bs->mr->romd_mode, bs->mr->ram, bs->mr->readonly, + bs->mr->nonvolatile, bs->mr->rom_device); + } + + /* Finally close UFFD file descriptor */ + uffd_close_fd(rs->uffdio_fd); + rs->uffdio_fd = -1; +#else + error_setg(&migrate_get_current()->error, + "Background-snapshot not supported on non-Linux hosts"); +#endif /* CONFIG_LINUX */ +} + static SaveVMHandlers savevm_ram_handlers = { .save_setup = ram_save_setup, .save_live_iterate = ram_save_iterate, diff --git a/migration/ram.h b/migration/ram.h index 011e85414e..0ec63e27ee 100644 --- a/migration/ram.h +++ b/migration/ram.h @@ -79,4 +79,8 @@ void colo_flush_ram_cache(void); void colo_release_ram_cache(void); void colo_incoming_start_dirty_log(void);+/* Background snapshots */+int ram_write_tracking_start(void); +void ram_write_tracking_stop(void); + #endif diff --git a/util/meson.build b/util/meson.build index f359af0d46..c64bfe94b3 100644 --- a/util/meson.build +++ b/util/meson.build @@ -50,6 +50,7 @@ endifif have_systemutil_ss.add(when: 'CONFIG_GIO', if_true: [files('dbus.c'), gio]) + util_ss.add(when: 'CONFIG_LINUX', if_true: files('userfaultfd.c')) endifif have_blockdiff --git a/util/userfaultfd.c b/util/userfaultfd.c new file mode 100644 index 0000000000..038953d7ed --- /dev/null +++ b/util/userfaultfd.c @@ -0,0 +1,215 @@ +/* + * Linux UFFD-WP support + * + * Copyright Virtuozzo GmbH, 2020 + * + * Authors: + * Andrey Gruzdev <andrey.gruz...@virtuozzo.com> + * + * This work is licensed under the terms of the GNU GPL, version 2 or + * later. See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "qemu/bitops.h" +#include "qemu/error-report.h" +#include "qemu/userfaultfd.h" +#include <poll.h> +#include <sys/syscall.h> +#include <sys/ioctl.h> + +/** + * uffd_create_fd: create UFFD file descriptor + * + * Returns non-negative file descriptor or negative value in case of an error + */ +int uffd_create_fd(void) +{ + int uffd; + struct uffdio_api api_struct; + uint64_t ioctl_mask = BIT(_UFFDIO_REGISTER) | BIT(_UFFDIO_UNREGISTER); + + uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); + if (uffd < 0) { + error_report("uffd_create_fd() failed: UFFD not supported");Please include the errno (or strerror(errno))
Ok.
+ return -1; + } + + api_struct.api = UFFD_API; + api_struct.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP; + if (ioctl(uffd, UFFDIO_API, &api_struct)) { + error_report("uffd_create_fd() failed: " + "API version not supported version=%llx errno=%i", + api_struct.api, errno); + goto fail; + } + + if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) { + error_report("uffd_create_fd() failed: " + "PAGEFAULT_FLAG_WP feature missing"); + goto fail; + } + + return uffd; + +fail: + close(uffd); + return -1; +}It would be great if we could find a way to share this with migration/postcopy-ram.c - this duplicates a lor of request_ufd_features.
Now I'm changing userfaultfd.c glue code to support also the postcopy requirenments - adding functionality to query UFFD feature support, glue for COPY_PAGE/ZERO_PAGE IOCTLs etc.
+ +/** + * uffd_close_fd: close UFFD file descriptor + * + * @uffd: UFFD file descriptor + */ +void uffd_close_fd(int uffd) +{ + assert(uffd >= 0); + close(uffd); +} + +/** + * uffd_register_memory: register memory range with UFFD + * + * Returns 0 in case of success, negative value on error + * + * @uffd: UFFD file descriptor + * @start: starting virtual address of memory range + * @length: length of memory range + * @track_missing: generate events on missing-page faults + * @track_wp: generate events on write-protected-page faults + */ +int uffd_register_memory(int uffd, hwaddr start, hwaddr length, + bool track_missing, bool track_wp) +{ + struct uffdio_register uffd_register; + + uffd_register.range.start = start; + uffd_register.range.len = length; + uffd_register.mode = (track_missing ? UFFDIO_REGISTER_MODE_MISSING : 0) | + (track_wp ? UFFDIO_REGISTER_MODE_WP : 0); + + if (ioctl(uffd, UFFDIO_REGISTER, &uffd_register)) { + error_report("uffd_register_memory() failed: " + "start=%0"PRIx64" len=%"PRIu64" mode=%llu errno=%i",PRIx64 for mode as well.
Ok.
+ start, length, uffd_register.mode, errno); + return -1; + } + + return 0; +} + +/** + * uffd_unregister_memory: un-register memory range with UFFD + * + * Returns 0 in case of success, negative value on error + * + * @uffd: UFFD file descriptor + * @start: starting virtual address of memory range + * @length: length of memory range + */ +int uffd_unregister_memory(int uffd, hwaddr start, hwaddr length) +{ + struct uffdio_range uffd_range; + + uffd_range.start = start; + uffd_range.len = length; + + if (ioctl(uffd, UFFDIO_UNREGISTER, &uffd_range)) { + error_report("uffd_unregister_memory() failed: " + "start=%0"PRIx64" len=%"PRIu64" errno=%i", + start, length, errno); + return -1; + } + + return 0; +} + +/** + * uffd_protect_memory: protect/unprotect memory range for writes with UFFD + * + * Returns 0 on success or negative value in case of error + * + * @uffd: UFFD file descriptor + * @start: starting virtual address of memory range + * @length: length of memory range + * @wp: write-protect/unprotect + */ +int uffd_protect_memory(int uffd, hwaddr start, hwaddr length, bool wp) +{ + struct uffdio_writeprotect uffd_writeprotect; + int res; + + uffd_writeprotect.range.start = start; + uffd_writeprotect.range.len = length; + uffd_writeprotect.mode = (wp ? UFFDIO_WRITEPROTECT_MODE_WP : 0); + + do { + res = ioctl(uffd, UFFDIO_WRITEPROTECT, &uffd_writeprotect); + } while (res < 0 && errno == EINTR); + if (res < 0) { + error_report("uffd_protect_memory() failed: " + "start=%0"PRIx64" len=%"PRIu64" mode=%llu errno=%i", + start, length, uffd_writeprotect.mode, errno); + return -1; + } + + return 0; +} + +/** + * uffd_read_events: read pending UFFD events + * + * Returns number of fetched messages, 0 if non is available or + * negative value in case of an error + * + * @uffd: UFFD file descriptor + * @msgs: pointer to message buffer + * @count: number of messages that can fit in the buffer + */ +int uffd_read_events(int uffd, struct uffd_msg *msgs, int count) +{ + ssize_t res; + do { + res = read(uffd, msgs, count * sizeof(struct uffd_msg)); + } while (res < 0 && errno == EINTR); + + if ((res < 0 && errno == EAGAIN)) { + return 0; + } + if (res < 0) { + error_report("uffd_read_events() failed: errno=%i", errno); + return -1; + } + + return (int) (res / sizeof(struct uffd_msg)); +} + +/** + * uffd_poll_events: poll UFFD file descriptor for read + * + * Returns true if events are available for read, false otherwise + * + * @uffd: UFFD file descriptor + * @tmo: timeout in milliseconds, 0 for non-blocking operation, + * negative value for infinite wait + */ +bool uffd_poll_events(int uffd, int tmo) +{ + int res; + struct pollfd poll_fd = { .fd = uffd, .events = POLLIN, .revents = 0 }; + + do { + res = poll(&poll_fd, 1, tmo); + } while (res < 0 && errno == EINTR); + + if (res == 0) { + return false; + } + if (res < 0) { + error_report("uffd_poll_events() failed: errno=%i", errno); + return false; + } + + return (poll_fd.revents & POLLIN) != 0; +} -- 2.25.1
--
Andrey Gruzdev, Principal Engineer
Virtuozzo GmbH +7-903-247-6397
virtuzzo.com
