From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35090) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YQfDk-0002Gs-4M for qemu-devel@nongnu.org; Wed, 25 Feb 2015 11:54:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YQfDe-0001TX-Pe for qemu-devel@nongnu.org; Wed, 25 Feb 2015 11:53:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49004) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YQfDe-0001TJ-Fb for qemu-devel@nongnu.org; Wed, 25 Feb 2015 11:53:54 -0500 From: "Dr. David Alan Gilbert (git)" Date: Wed, 25 Feb 2015 16:52:03 +0000 Message-Id: <1424883128-9841-41-git-send-email-dgilbert@redhat.com> In-Reply-To: <1424883128-9841-1-git-send-email-dgilbert@redhat.com> References: <1424883128-9841-1-git-send-email-dgilbert@redhat.com> Subject: [Qemu-devel] [PATCH v5 40/45] 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, yanghy@cn.fujitsu.com, david@gibson.dropbear.id.au 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 | 217 ++++++++++++++++++++++++++++++++++++++++-- trace-events | 12 +++ 3 files changed, 223 insertions(+), 10 deletions(-) diff --git a/include/migration/migration.h b/include/migration/migration.h index 139bb1b..cec064f 100644 --- a/include/migration/migration.h +++ b/include/migration/migration.h @@ -86,11 +86,15 @@ struct MigrationIncomingState { PostcopyState postcopy_state; + 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 */ PostcopyPMI postcopy_pmi; diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index 86fa5a0..abc039e 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -47,6 +47,8 @@ struct PostcopyDiscardState { */ #if defined(__linux__) +#include +#include #include #include #include @@ -264,7 +266,7 @@ void postcopy_pmi_dump(MigrationIncomingState *mis) void postcopy_hook_early_receive(MigrationIncomingState *mis, size_t bitmap_index) { - if (mis->postcopy_state == POSTCOPY_INCOMING_ADVISE) { + if (postcopy_state_get(mis) == POSTCOPY_INCOMING_ADVISE) { /* * If we're in precopy-advise mode we need to track received pages even * though we don't need to place pages atomically yet. @@ -489,15 +491,40 @@ 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 */ + perror("incing userfault_quit_fd"); + } + 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; } @@ -531,36 +558,206 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr, } /* + * Tell the kernel that we've now got some memory it previously asked for. + */ +static int ack_userfault(MigrationIncomingState *mis, void *start, size_t len) +{ + struct uffdio_range range_struct; + + range_struct.start = (uint64_t)(uintptr_t)start; + range_struct.len = (uint64_t)len; + + errno = 0; + if (ioctl(mis->userfault_fd, UFFDIO_WAKE, &range_struct)) { + int e = errno; + + if (e == ENOENT) { + /* Kernel said it wasn't waiting - one case where this can + * happen is where two threads triggered the userfault + * and we receive the page and ack it just after we received + * the 2nd request and that ends up deciding it should ack it + * We could optimise it out, but it's rare. + */ + /*fprintf(stderr, "ack_userfault: %p/%zx ENOENT\n", start, len); */ + return 0; + } + error_report("postcopy_ram: Failed to notify kernel for %p/%zx (%d)", + start, len, e); + return -e; + } + + return 0; +} + +/* * Handle faults detected by the USERFAULT markings */ 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) { + perror("mapping local tmp page"); + return NULL; } + if (madvise(local_tmp_page, getpagesize(), MADV_DONTFORK)) { + munmap(local_tmp_page, getpagesize()); + perror("postcpy local page DONTFORK"); + return NULL; + } + + while (true) { + PostcopyPMIState old_state, tmp_state; + ram_addr_t rb_offset; + ram_addr_t in_raspace; + unsigned long bitmap_index; + 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) { + perror("userfault poll"); + 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 (ret < 0) { + perror("Failed to read full userfault hostaddr"); + 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, &bitmap_index); + if (!rb) { + error_report("postcopy_ram_fault_thread: Fault outside guest: %" + PRIx64, hostaddr); + break; + } + trace_postcopy_ram_fault_thread_request(hostaddr, bitmap_index, + qemu_ram_get_idstr(rb), + rb_offset); + + tmp_state = postcopy_pmi_get_state(mis, bitmap_index); + do { + old_state = tmp_state; + + switch (old_state) { + case POSTCOPY_PMI_REQUESTED: + /* Do nothing - it's already requested */ + break; + + case POSTCOPY_PMI_RECEIVED: + /* Already arrived - no state change, just kick the kernel */ + trace_postcopy_ram_fault_thread_notify_pre(hostaddr); + if (ack_userfault(mis, + (void *)((uintptr_t)hostaddr + & ~(hostpagesize - 1)), + hostpagesize)) { + assert(0); + } + break; + + case POSTCOPY_PMI_MISSING: + tmp_state = postcopy_pmi_change_state(mis, bitmap_index, + old_state, POSTCOPY_PMI_REQUESTED); + if (tmp_state == POSTCOPY_PMI_MISSING) { + /* + * 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); + } + } /* else it just arrived from the source and the kernel will + be kicked during the receive */ + break; + } + } while (tmp_state != old_state); + } + 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); + if (mis->userfault_fd == -1) { + perror("Failed to open userfault fd"); + 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) { + perror("Opening userfault_quit_fd"); + 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 16a91d9..d955a28 100644 --- a/trace-events +++ b/trace-events @@ -1498,6 +1498,18 @@ postcopy_discard_send_finish(const char *ramblock, int nwords, int ncmds) "%s ma postcopy_cleanup_area(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx" postcopy_init_area(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx" postcopy_place_page(unsigned long offset, void *host_addr, bool all_zero, int old_state) "offset=%lx host=%p all_zero=%d old_state=%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, unsigned long index, const char *ramblock, size_t offset) "Request for HVA=%" PRIx64 " index=%lx rb=%s offset=%zx" +postcopy_ram_fault_thread_notify_pre(uint64_t hostaddr) "%" PRIx64 +postcopy_ram_fault_thread_notify_zero(void *hostaddr) "%p" +postcopy_ram_fault_thread_notify_zero_ack(void *hostaddr, unsigned long bitmap_index) "%p %lx" +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