* source to the destination before all the data has been copied.
*/
-#include <glib.h>
-#include <stdio.h>
-#include <unistd.h>
+#include "qemu/osdep.h"
#include "qemu-common.h"
#include "migration/migration.h"
#include "migration/postcopy-ram.h"
#include "sysemu/sysemu.h"
+#include "sysemu/balloon.h"
#include "qemu/error-report.h"
#include "trace.h"
*/
#if defined(__linux__)
-#include <sys/mman.h>
+#include <poll.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
-#include <sys/types.h>
#include <asm/types.h> /* for __u64 */
#endif
-#if defined(__linux__) && defined(__NR_userfaultfd)
+#if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD)
+#include <sys/eventfd.h>
#include <linux/userfaultfd.h>
static bool ufd_version_check(int ufd)
return false;
}
+ if (getpagesize() != ram_pagesize_summary()) {
+ bool have_hp = false;
+ /* We've got a huge page */
+#ifdef UFFD_FEATURE_MISSING_HUGETLBFS
+ have_hp = api_struct.features & UFFD_FEATURE_MISSING_HUGETLBFS;
+#endif
+ if (!have_hp) {
+ error_report("Userfault on this host does not support huge pages");
+ return false;
+ }
+ }
return true;
}
+/* Callback from postcopy_ram_supported_by_host block iterator.
+ */
+static int test_range_shared(const char *block_name, void *host_addr,
+ ram_addr_t offset, ram_addr_t length, void *opaque)
+{
+ if (qemu_ram_is_shared(qemu_ram_block_by_name(block_name))) {
+ error_report("Postcopy on shared RAM (%s) is not yet supported",
+ block_name);
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * Note: This has the side effect of munlock'ing all of RAM, that's
+ * normally fine since if the postcopy succeeds it gets turned back on at the
+ * end.
+ */
bool postcopy_ram_supported_by_host(void)
{
long pagesize = getpagesize();
goto out;
}
+ /* We don't support postcopy with shared RAM yet */
+ if (qemu_ram_foreach_block(test_range_shared, NULL)) {
+ goto out;
+ }
+
+ /*
+ * userfault and mlock don't go together; we'll put it back later if
+ * it was enabled.
+ */
+ if (munlockall()) {
+ error_report("%s: munlockall: %s", __func__, strerror(errno));
+ return -1;
+ }
+
/*
* We need to check that the ops we need are supported on anon memory
* To do that we need to register a chunk and see the flags that
return ret;
}
-/**
- * postcopy_ram_discard_range: Discard a range of memory.
- * We can assume that if we've been called postcopy_ram_hosttest returned true.
- *
- * @mis: Current incoming migration state.
- * @start, @length: range of memory to discard.
- *
- * returns: 0 on success.
- */
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
- size_t length)
-{
- trace_postcopy_ram_discard_range(start, length);
- if (madvise(start, length, MADV_DONTNEED)) {
- error_report("%s MADV_DONTNEED: %s", __func__, strerror(errno));
- return -1;
- }
-
- return 0;
-}
-
/*
* Setup an area of RAM so that it *can* be used for postcopy later; this
* must be done right at the start prior to pre-copy.
* - we're going to get the copy from the source anyway.
* (Precopy will just overwrite this data, so doesn't need the discard)
*/
- if (postcopy_ram_discard_range(mis, host_addr, length)) {
+ if (ram_discard_range(mis, block_name, 0, length)) {
return -1;
}
* We turned off hugepage for the precopy stage with postcopy enabled
* we can turn it back on now.
*/
-#ifdef MADV_HUGEPAGE
- if (madvise(host_addr, length, MADV_HUGEPAGE)) {
- error_report("%s HUGEPAGE: %s", __func__, strerror(errno));
- return -1;
- }
-#endif
+ qemu_madvise(host_addr, length, QEMU_MADV_HUGEPAGE);
/*
* We can also turn off userfault now since we should have all the
*/
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_range, mis)) {
+ trace_postcopy_ram_incoming_cleanup_entry();
+
+ if (mis->have_fault_thread) {
+ uint64_t tmp64;
+
+ if (qemu_ram_foreach_block(cleanup_range, mis)) {
+ return -1;
+ }
+ /*
+ * Tell the fault_thread to exit, it's an eventfd that should
+ * currently be at 0, we're going to increment 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: incrementing 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;
+ }
+
+ qemu_balloon_inhibit(false);
+
+ if (enable_mlock) {
+ if (os_mlock() < 0) {
+ error_report("mlock: %s", strerror(errno));
+ /*
+ * It doesn't feel right to fail at this point, we have a valid
+ * VM state.
+ */
+ }
+ }
+
+ postcopy_state_set(POSTCOPY_INCOMING_END);
+ migrate_send_rp_shut(mis, qemu_file_get_error(mis->from_src_file) != 0);
+
+ if (mis->postcopy_tmp_page) {
+ munmap(mis->postcopy_tmp_page, mis->largest_page_size);
+ mis->postcopy_tmp_page = NULL;
+ }
+ if (mis->postcopy_tmp_zero_page) {
+ munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size);
+ mis->postcopy_tmp_zero_page = NULL;
+ }
+ trace_postcopy_ram_incoming_cleanup_exit();
+ return 0;
+}
+
+/*
+ * Disable huge pages on an area
+ */
+static int nhp_range(const char *block_name, void *host_addr,
+ ram_addr_t offset, ram_addr_t length, void *opaque)
+{
+ trace_postcopy_nhp_range(block_name, host_addr, offset, length);
+
+ /*
+ * Before we do discards we need to ensure those discards really
+ * do delete areas of the page, even if THP thinks a hugepage would
+ * be a good idea, so force hugepages off.
+ */
+ qemu_madvise(host_addr, length, QEMU_MADV_NOHUGEPAGE);
+
+ return 0;
+}
+
+/*
+ * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
+ * however leaving it until after precopy means that most of the precopy
+ * data is still THPd
+ */
+int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
+{
+ if (qemu_ram_foreach_block(nhp_range, mis)) {
return -1;
}
+ postcopy_state_set(POSTCOPY_INCOMING_DISCARD);
+
return 0;
}
error_report("%s userfault register: %s", __func__, strerror(errno));
return -1;
}
+ if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) {
+ error_report("%s userfault: Region doesn't support COPY", __func__);
+ return -1;
+ }
return 0;
}
static void *postcopy_ram_fault_thread(void *opaque)
{
MigrationIncomingState *mis = opaque;
+ struct uffd_msg msg;
+ int ret;
+ RAMBlock *rb = NULL;
+ RAMBlock *last_rb = NULL; /* last RAMBlock we sent part of */
- fprintf(stderr, "postcopy_ram_fault_thread\n");
- /* TODO: In later patch */
+ trace_postcopy_ram_fault_thread_entry();
qemu_sem_post(&mis->fault_thread_sem);
- while (1) {
- /* TODO: In later patch */
- }
+ while (true) {
+ ram_addr_t rb_offset;
+ 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, &msg, sizeof(msg));
+ if (ret != sizeof(msg)) {
+ 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 message: %s",
+ __func__, strerror(errno));
+ break;
+ } else {
+ error_report("%s: Read %d bytes from userfaultfd expected %zd",
+ __func__, ret, sizeof(msg));
+ break; /* Lost alignment, don't know what we'd read next */
+ }
+ }
+ if (msg.event != UFFD_EVENT_PAGEFAULT) {
+ error_report("%s: Read unexpected event %ud from userfaultfd",
+ __func__, msg.event);
+ continue; /* It's not a page fault, shouldn't happen */
+ }
+
+ rb = qemu_ram_block_from_host(
+ (void *)(uintptr_t)msg.arg.pagefault.address,
+ true, &rb_offset);
+ if (!rb) {
+ error_report("postcopy_ram_fault_thread: Fault outside guest: %"
+ PRIx64, (uint64_t)msg.arg.pagefault.address);
+ break;
+ }
+
+ rb_offset &= ~(qemu_ram_pagesize(rb) - 1);
+ trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address,
+ 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, qemu_ram_pagesize(rb));
+ } else {
+ /* Save some space */
+ migrate_send_rp_req_pages(mis, NULL,
+ rb_offset, qemu_ram_pagesize(rb));
+ }
+ }
+ 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;
}
+ /*
+ * Ballooning can mark pages as absent while we're postcopying
+ * that would cause false userfaults.
+ */
+ qemu_balloon_inhibit(true);
+
+ trace_postcopy_ram_enable_notify();
+
return 0;
}
+/*
+ * Place a host page (from) at (host) atomically
+ * returns 0 on success
+ */
+int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
+ size_t pagesize)
+{
+ struct uffdio_copy copy_struct;
+
+ copy_struct.dst = (uint64_t)(uintptr_t)host;
+ copy_struct.src = (uint64_t)(uintptr_t)from;
+ copy_struct.len = pagesize;
+ copy_struct.mode = 0;
+
+ /* copy also acks to the kernel waking the stalled thread up
+ * TODO: We can inhibit that ack and only do it if it was requested
+ * which would be slightly cheaper, but we'd have to be careful
+ * of the order of updating our page state.
+ */
+ if (ioctl(mis->userfault_fd, UFFDIO_COPY, ©_struct)) {
+ int e = errno;
+ error_report("%s: %s copy host: %p from: %p (size: %zd)",
+ __func__, strerror(e), host, from, pagesize);
+
+ return -e;
+ }
+
+ trace_postcopy_place_page(host);
+ return 0;
+}
+
+/*
+ * Place a zero page at (host) atomically
+ * returns 0 on success
+ */
+int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
+ size_t pagesize)
+{
+ trace_postcopy_place_page_zero(host);
+
+ if (pagesize == getpagesize()) {
+ struct uffdio_zeropage zero_struct;
+ zero_struct.range.start = (uint64_t)(uintptr_t)host;
+ zero_struct.range.len = getpagesize();
+ zero_struct.mode = 0;
+
+ if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {
+ int e = errno;
+ error_report("%s: %s zero host: %p",
+ __func__, strerror(e), host);
+
+ return -e;
+ }
+ } else {
+ /* The kernel can't use UFFDIO_ZEROPAGE for hugepages */
+ if (!mis->postcopy_tmp_zero_page) {
+ mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size,
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0);
+ if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
+ int e = errno;
+ mis->postcopy_tmp_zero_page = NULL;
+ error_report("%s: %s mapping large zero page",
+ __func__, strerror(e));
+ return -e;
+ }
+ memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
+ }
+ return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page,
+ pagesize);
+ }
+
+ return 0;
+}
+
+/*
+ * Returns a target page of memory that can be mapped at a later point in time
+ * using postcopy_place_page
+ * The same address is used repeatedly, postcopy_place_page just takes the
+ * backing page away.
+ * Returns: Pointer to allocated page
+ *
+ */
+void *postcopy_get_tmp_page(MigrationIncomingState *mis)
+{
+ if (!mis->postcopy_tmp_page) {
+ mis->postcopy_tmp_page = mmap(NULL, mis->largest_page_size,
+ PROT_READ | PROT_WRITE, MAP_PRIVATE |
+ MAP_ANONYMOUS, -1, 0);
+ if (mis->postcopy_tmp_page == MAP_FAILED) {
+ mis->postcopy_tmp_page = NULL;
+ error_report("%s: %s", __func__, strerror(errno));
+ return NULL;
+ }
+ }
+
+ return mis->postcopy_tmp_page;
+}
+
#else
/* No target OS support, stubs just fail */
bool postcopy_ram_supported_by_host(void)
return -1;
}
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
- size_t length)
+int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
{
assert(0);
return -1;
assert(0);
return -1;
}
+
+int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
+ size_t pagesize)
+{
+ assert(0);
+ return -1;
+}
+
+int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
+ size_t pagesize)
+{
+ assert(0);
+ return -1;
+}
+
+void *postcopy_get_tmp_page(MigrationIncomingState *mis)
+{
+ assert(0);
+ return NULL;
+}
+
#endif
/* ------------------------------------------------------------------------- */
if (pds->cur_entry == MAX_DISCARDS_PER_COMMAND) {
/* Full set, ship it! */
- qemu_savevm_send_postcopy_ram_discard(ms->file, pds->ramblock_name,
+ qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
+ pds->ramblock_name,
pds->cur_entry,
pds->start_list,
pds->length_list);
{
/* Anything unsent? */
if (pds->cur_entry) {
- qemu_savevm_send_postcopy_ram_discard(ms->file, pds->ramblock_name,
+ qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
+ pds->ramblock_name,
pds->cur_entry,
pds->start_list,
pds->length_list);
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