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Wed, 25 Nov 2020 19:17:04 +0000 Subject: Re: [PATCH v3 2/7] introduce UFFD-WP low-level interface helpers To: "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, Den Lunev , Eric Blake , Paolo Bonzini , Juan Quintela , Markus Armbruster , Peter Xu References: <20201119125940.20017-1-andrey.gruzdev@virtuozzo.com> <20201119125940.20017-3-andrey.gruzdev@virtuozzo.com> <20201124175712.GM3366@work-vm> <24483c0d-107f-427e-87b1-f4e039bfe486@virtuozzo.com> <20201125184307.GJ3222@work-vm> From: Andrey Gruzdev Message-ID: Date: Wed, 25 Nov 2020 22:17:02 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20201125184307.GJ3222@work-vm> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [95.165.26.68] X-ClientProxiedBy: AM4P190CA0009.EURP190.PROD.OUTLOOK.COM (2603:10a6:200:56::19) To VI1PR0802MB2510.eurprd08.prod.outlook.com (2603:10a6:800:ad::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.64] (95.165.26.68) by AM4P190CA0009.EURP190.PROD.OUTLOOK.COM (2603:10a6:200:56::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3611.20 via Frontend Transport; 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envelope-from=andrey.gruzdev@virtuozzo.com; helo=EUR05-DB8-obe.outbound.protection.outlook.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 25.11.2020 21:43, Dr. David Alan Gilbert wrote: > * Andrey Gruzdev (andrey.gruzdev@virtuozzo.com) wrote: >> On 24.11.2020 20:57, Dr. David Alan Gilbert wrote: >>> * Andrey Gruzdev (andrey.gruzdev@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 >>>> --- >>>> include/exec/memory.h | 7 ++ >>>> migration/ram.c | 267 ++++++++++++++++++++++++++++++++++++++++++ >>>> migration/ram.h | 4 + >>>> 3 files changed, 278 insertions(+) >>>> >>>> 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/migration/ram.c b/migration/ram.c >>>> index 7811cde643..7f273c9996 100644 >>>> --- a/migration/ram.c >>>> +++ b/migration/ram.c >>>> @@ -56,6 +56,12 @@ >>>> #include "savevm.h" >>>> #include "qemu/iov.h" >>>> #include "multifd.h" >>>> +#include >>>> +#include >>>> +#include >>>> +#include >>>> +#include >>>> +#include "sysemu/runstate.h" >>>> /***********************************************************/ >>>> /* ram save/restore */ >>>> @@ -298,6 +304,8 @@ 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 */ >>>> @@ -453,6 +461,181 @@ static QemuThread *decompress_threads; >>>> static QemuMutex decomp_done_lock; >>>> static QemuCond decomp_done_cond; >>>> +/** >>>> + * uffd_create_fd: create UFFD file descriptor >>>> + * >>>> + * Returns non-negative file descriptor or negative value in case of an error >>>> + */ >>>> +static int uffd_create_fd(void) >>>> +{ >>>> + int uffd; >>>> + struct uffdio_api api_struct; >>>> + uint64_t ioctl_mask = BIT(_UFFDIO_REGISTER) | BIT(_UFFDIO_UNREGISTER); >>> >>> You need to be a bit careful about doing this in migration/ram.c - it's >>> generic code; at minimum it needs ifdef'ing for Linux. >>> >> >> Yes, it's totally linux-specific, I think better to move this code out of >> migration/ram.c, as Peter proposed. >> >>>> + uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); >>>> + if (uffd < 0) { >>>> + error_report("uffd_create_fd() failed: UFFD not supported"); >>>> + 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; >>> >>> Should we be putting that somewher that we can share with postcopy? >>> >> >> Sure, maybe to util/uffd-wp.c + include/qemu/uffd-wp.h. >> What do you think? > > Or how about a userfaultfd.c somewhere? > > Dave > For userfaultfd.c I'm also ok. Andrey >>>> +fail: >>>> + close(uffd); >>>> + return -1; >>>> +} >>>> + >>>> +/** >>>> + * uffd_close_fd: close UFFD file descriptor >>>> + * >>>> + * @uffd: UFFD file descriptor >>>> + */ >>>> +static 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 >>>> + */ >>>> +static 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", >>>> + start, length, uffd_register.mode, 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 >>>> + */ >>>> +static 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; >>>> +} >>>> + >>>> +__attribute__ ((unused)) >>>> +static int uffd_read_events(int uffd, struct uffd_msg *msgs, int count); >>>> +__attribute__ ((unused)) >>>> +static bool uffd_poll_events(int uffd, int tmo); >>>> + >>>> +/** >>>> + * 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 >>>> + */ >>>> +static 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 >>>> + */ >>>> +static 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; >>>> +} >>>> + >>>> static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block, >>>> ram_addr_t offset, uint8_t *source_buf); >>>> @@ -3788,6 +3971,90 @@ 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) >>>> +{ >>>> + 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; >>>> + } >>>> + >>>> + /* 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; >>>> + } >>>> + bs->flags |= RAM_UF_WRITEPROTECT; >>>> + >>>> + 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: >>>> + uffd_close_fd(uffd); >>>> + rs->uffdio_fd = -1; >>>> + return -1; >>>> +} >>>> + >>>> +/** >>>> + * ram_write_tracking_stop: stop UFFD-WP memory tracking and remove protection >>>> + */ >>>> +void ram_write_tracking_stop(void) >>>> +{ >>>> + RAMState *rs = ram_state; >>>> + RAMBlock *bs; >>>> + assert(rs->uffdio_fd >= 0); >>>> + >>>> + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { >>>> + if ((bs->flags & RAM_UF_WRITEPROTECT) == 0) { >>>> + continue; >>>> + } >>>> + 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); >>>> + /* Cleanup flags */ >>>> + bs->flags &= ~RAM_UF_WRITEPROTECT; >>>> + } >>>> + >>>> + /* >>>> + * Close UFFD file descriptor to remove protection, >>>> + * release registered memory regions and flush wait queues >>>> + */ >>>> + uffd_close_fd(rs->uffdio_fd); >>>> + rs->uffdio_fd = -1; >>>> +} >>>> + >>>> 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..3611cb51de 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); >>>> +/* Live snapshots */ >>>> +int ram_write_tracking_start(void); >>>> +void ram_write_tracking_stop(void); >>>> + >>>> #endif >>>> -- >>>> 2.25.1 >>>> >> >> >> -- >> Andrey Gruzdev, Principal Engineer >> Virtuozzo GmbH +7-903-247-6397 >> virtuzzo.com >> -- Andrey Gruzdev, Principal Engineer Virtuozzo GmbH +7-903-247-6397 virtuzzo.com