From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50428) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yi4Hm-0007po-Se for qemu-devel@nongnu.org; Tue, 14 Apr 2015 13:06:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Yi4Hl-00034P-4r for qemu-devel@nongnu.org; Tue, 14 Apr 2015 13:06:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34718) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yi4Hk-000341-SC for qemu-devel@nongnu.org; Tue, 14 Apr 2015 13:06:05 -0400 From: "Dr. David Alan Gilbert (git)" Date: Tue, 14 Apr 2015 18:04:08 +0100 Message-Id: <1429031053-4454-43-git-send-email-dgilbert@redhat.com> In-Reply-To: <1429031053-4454-1-git-send-email-dgilbert@redhat.com> References: <1429031053-4454-1-git-send-email-dgilbert@redhat.com> Subject: [Qemu-devel] [PATCH v6 42/47] Postcopy; Handle userfault requests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, quintela@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au, yayanghy@cn.fujitsu.com From: "Dr. David Alan Gilbert" userfaultfd is a Linux syscall that gives an fd that receives a stream of notifications of accesses to pages registered with it and allows the program to acknowledge those stalls and tell the accessing thread to carry on. Signed-off-by: Dr. David Alan Gilbert --- include/migration/migration.h | 4 + migration/postcopy-ram.c | 165 +++++++++++++++++++++++++++++++++++++++--- trace-events | 9 +++ 3 files changed, 169 insertions(+), 9 deletions(-) diff --git a/include/migration/migration.h b/include/migration/migration.h index db06fd2..4d6f33a 100644 --- a/include/migration/migration.h +++ b/include/migration/migration.h @@ -75,11 +75,15 @@ struct MigrationIncomingState { */ QemuEvent main_thread_load_event; + bool have_fault_thread; QemuThread fault_thread; QemuSemaphore fault_thread_sem; /* For the kernel to send us notifications */ int userfault_fd; + /* To tell the fault_thread to quit */ + int userfault_quit_fd; + QEMUFile *return_path; QemuMutex rp_mutex; /* We send replies from multiple threads */ void *postcopy_tmp_page; diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index 33aadbc..b2dc3b7 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -49,6 +49,8 @@ struct PostcopyDiscardState { */ #if defined(__linux__) +#include +#include #include #include #include @@ -273,15 +275,41 @@ int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages) */ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) { - /* TODO: Join the fault thread once we're sure it will exit */ - if (qemu_ram_foreach_block(cleanup_area, mis)) { - return -1; + trace_postcopy_ram_incoming_cleanup_entry(); + + if (mis->have_fault_thread) { + uint64_t tmp64; + + if (qemu_ram_foreach_block(cleanup_area, mis)) { + return -1; + } + /* + * Tell the fault_thread to exit, it's an eventfd that should + * currently be at 0, we're going to inc it to 1 + */ + tmp64 = 1; + if (write(mis->userfault_quit_fd, &tmp64, 8) == 8) { + trace_postcopy_ram_incoming_cleanup_join(); + qemu_thread_join(&mis->fault_thread); + } else { + /* Not much we can do here, but may as well report it */ + error_report("%s: incing userfault_quit_fd: %s", __func__, + strerror(errno)); + } + trace_postcopy_ram_incoming_cleanup_closeuf(); + close(mis->userfault_fd); + close(mis->userfault_quit_fd); + mis->have_fault_thread = false; } + postcopy_state_set(mis, POSTCOPY_INCOMING_END); + migrate_send_rp_shut(mis, qemu_file_get_error(mis->file) != 0); + if (mis->postcopy_tmp_page) { munmap(mis->postcopy_tmp_page, getpagesize()); mis->postcopy_tmp_page = NULL; } + trace_postcopy_ram_incoming_cleanup_exit(); return 0; } @@ -320,31 +348,150 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr, static void *postcopy_ram_fault_thread(void *opaque) { MigrationIncomingState *mis = (MigrationIncomingState *)opaque; - - fprintf(stderr, "postcopy_ram_fault_thread\n"); - /* TODO: In later patch */ + uint64_t hostaddr; /* The kernel always gives us 64 bit, not a pointer */ + int ret; + size_t hostpagesize = getpagesize(); + RAMBlock *rb = NULL; + RAMBlock *last_rb = NULL; /* last RAMBlock we sent part of */ + uint8_t *local_tmp_page; + + trace_postcopy_ram_fault_thread_entry(); qemu_sem_post(&mis->fault_thread_sem); - while (1) { - /* TODO: In later patch */ + + local_tmp_page = mmap(NULL, getpagesize(), + PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, + -1, 0); + if (!local_tmp_page) { + error_report("%s mapping local tmp page: %s", __func__, + strerror(errno)); + return NULL; } + if (madvise(local_tmp_page, getpagesize(), MADV_DONTFORK)) { + munmap(local_tmp_page, getpagesize()); + error_report("%s postcopy local page DONTFORK: %s", __func__, + strerror(errno)); + return NULL; + } + + while (true) { + ram_addr_t rb_offset; + ram_addr_t in_raspace; + struct pollfd pfd[2]; + + /* + * We're mainly waiting for the kernel to give us a faulting HVA, + * however we can be told to quit via userfault_quit_fd which is + * an eventfd + */ + pfd[0].fd = mis->userfault_fd; + pfd[0].events = POLLIN; + pfd[0].revents = 0; + pfd[1].fd = mis->userfault_quit_fd; + pfd[1].events = POLLIN; /* Waiting for eventfd to go positive */ + pfd[1].revents = 0; + + if (poll(pfd, 2, -1 /* Wait forever */) == -1) { + error_report("%s: userfault poll: %s", __func__, strerror(errno)); + break; + } + + if (pfd[1].revents) { + trace_postcopy_ram_fault_thread_quit(); + break; + } + + ret = read(mis->userfault_fd, &hostaddr, sizeof(hostaddr)); + if (ret != sizeof(hostaddr)) { + if (errno == EAGAIN) { + /* + * if a wake up happens on the other thread just after + * the poll, there is nothing to read. + */ + continue; + } + if (ret < 0) { + error_report("%s: Failed to read full userfault hostaddr: %s", + __func__, strerror(errno)); + break; + } else { + error_report("%s: Read %d bytes from userfaultfd expected %zd", + __func__, ret, sizeof(hostaddr)); + break; /* Lost alignment, don't know what we'd read next */ + } + } + rb = qemu_ram_block_from_host((void *)(uintptr_t)hostaddr, true, + &in_raspace, &rb_offset); + if (!rb) { + error_report("postcopy_ram_fault_thread: Fault outside guest: %" + PRIx64, hostaddr); + break; + } + + trace_postcopy_ram_fault_thread_request(hostaddr, + qemu_ram_get_idstr(rb), + rb_offset); + + /* + * Send the request to the source - we want to request one + * of our host page sizes (which is >= TPS) + */ + if (rb != last_rb) { + last_rb = rb; + migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb), + rb_offset, hostpagesize); + } else { + /* Save some space */ + migrate_send_rp_req_pages(mis, NULL, + rb_offset, hostpagesize); + } + } + munmap(local_tmp_page, getpagesize()); + trace_postcopy_ram_fault_thread_exit(); return NULL; } int postcopy_ram_enable_notify(MigrationIncomingState *mis) { - /* Create the fault handler thread and wait for it to be ready */ + /* Open the fd for the kernel to give us userfaults */ + mis->userfault_fd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); + if (mis->userfault_fd == -1) { + error_report("%s: Failed to open userfault fd: %s", __func__, + strerror(errno)); + return -1; + } + + /* + * Although the host check already tested the API, we need to + * do the check again as an ABI handshake on the new fd. + */ + if (!ufd_version_check(mis->userfault_fd)) { + return -1; + } + + /* Now an eventfd we use to tell the fault-thread to quit */ + mis->userfault_quit_fd = eventfd(0, EFD_CLOEXEC); + if (mis->userfault_quit_fd == -1) { + error_report("%s: Opening userfault_quit_fd: %s", __func__, + strerror(errno)); + close(mis->userfault_fd); + return -1; + } + qemu_sem_init(&mis->fault_thread_sem, 0); qemu_thread_create(&mis->fault_thread, "postcopy/fault", postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE); qemu_sem_wait(&mis->fault_thread_sem); qemu_sem_destroy(&mis->fault_thread_sem); + mis->have_fault_thread = true; /* Mark so that we get notified of accesses to unwritten areas */ if (qemu_ram_foreach_block(ram_block_enable_notify, mis)) { return -1; } + trace_postcopy_ram_enable_notify(); + return 0; } diff --git a/trace-events b/trace-events index b65740c..72a65fa 100644 --- a/trace-events +++ b/trace-events @@ -1500,6 +1500,15 @@ postcopy_cleanup_area(const char *ramblock, void *host_addr, size_t offset, size postcopy_ram_discard_range(void *start, void *end) "%p,%p" postcopy_init_area(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx" postcopy_place_page(void *host_addr, bool all_zero) "host=%p all_zero=%d" +postcopy_ram_enable_notify(void) "" +postcopy_ram_fault_thread_entry(void) "" +postcopy_ram_fault_thread_exit(void) "" +postcopy_ram_fault_thread_quit(void) "" +postcopy_ram_fault_thread_request(uint64_t hostaddr, const char *ramblock, size_t offset) "Request for HVA=%" PRIx64 " rb=%s offset=%zx" +postcopy_ram_incoming_cleanup_closeuf(void) "" +postcopy_ram_incoming_cleanup_entry(void) "" +postcopy_ram_incoming_cleanup_exit(void) "" +postcopy_ram_incoming_cleanup_join(void) "" # kvm-all.c kvm_ioctl(int type, void *arg) "type 0x%x, arg %p" -- 2.1.0