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qemu/migration/postcopy-ram.c
Dr. David Alan Gilbert 29d8fa7f73 postcopy: Allow shared memory 
Now that we have the mechanisms in here, allow shared memory in a
postcopy.

Note that QEMU can't tell who all the users of shared regions are
and thus can't tell whether all the users of the shared regions
have appropriate support for postcopy.  Those devices that explicitly
support shared memory (e.g. vhost-user) must check, but it doesn't
stop weirder configurations causing problems.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2018-03-20 16:40:37 +02:00

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/*
* Postcopy migration for RAM
*
* Copyright 2013-2015 Red Hat, Inc. and/or its affiliates
*
* Authors:
* Dave Gilbert <dgilbert@redhat.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.
*
*/
/*
* Postcopy is a migration technique where the execution flips from the
* source to the destination before all the data has been copied.
*/
#include "qemu/osdep.h"
#include "exec/target_page.h"
#include "migration.h"
#include "qemu-file.h"
#include "savevm.h"
#include "postcopy-ram.h"
#include "ram.h"
#include "qapi/error.h"
#include "qemu/notify.h"
#include "sysemu/sysemu.h"
#include "sysemu/balloon.h"
#include "qemu/error-report.h"
#include "trace.h"
/* Arbitrary limit on size of each discard command,
* keeps them around ~200 bytes
*/
#define MAX_DISCARDS_PER_COMMAND 12
struct PostcopyDiscardState {
const char *ramblock_name;
uint16_t cur_entry;
/*
* Start and length of a discard range (bytes)
*/
uint64_t start_list[MAX_DISCARDS_PER_COMMAND];
uint64_t length_list[MAX_DISCARDS_PER_COMMAND];
unsigned int nsentwords;
unsigned int nsentcmds;
};
static NotifierWithReturnList postcopy_notifier_list;
void postcopy_infrastructure_init(void)
{
notifier_with_return_list_init(&postcopy_notifier_list);
}
void postcopy_add_notifier(NotifierWithReturn *nn)
{
notifier_with_return_list_add(&postcopy_notifier_list, nn);
}
void postcopy_remove_notifier(NotifierWithReturn *n)
{
notifier_with_return_remove(n);
}
int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp)
{
struct PostcopyNotifyData pnd;
pnd.reason = reason;
pnd.errp = errp;
return notifier_with_return_list_notify(&postcopy_notifier_list,
&pnd);
}
/* Postcopy needs to detect accesses to pages that haven't yet been copied
* across, and efficiently map new pages in, the techniques for doing this
* are target OS specific.
*/
#if defined(__linux__)
#include <poll.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <asm/types.h> /* for __u64 */
#endif
#if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD)
#include <sys/eventfd.h>
#include <linux/userfaultfd.h>
/**
* receive_ufd_features: check userfault fd features, to request only supported
* features in the future.
*
* Returns: true on success
*
* __NR_userfaultfd - should be checked before
* @features: out parameter will contain uffdio_api.features provided by kernel
* in case of success
*/
static bool receive_ufd_features(uint64_t *features)
{
struct uffdio_api api_struct = {0};
int ufd;
bool ret = true;
/* if we are here __NR_userfaultfd should exists */
ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
if (ufd == -1) {
error_report("%s: syscall __NR_userfaultfd failed: %s", __func__,
strerror(errno));
return false;
}
/* ask features */
api_struct.api = UFFD_API;
api_struct.features = 0;
if (ioctl(ufd, UFFDIO_API, &api_struct)) {
error_report("%s: UFFDIO_API failed: %s", __func__,
strerror(errno));
ret = false;
goto release_ufd;
}
*features = api_struct.features;
release_ufd:
close(ufd);
return ret;
}
/**
* request_ufd_features: this function should be called only once on a newly
* opened ufd, subsequent calls will lead to error.
*
* Returns: true on succes
*
* @ufd: fd obtained from userfaultfd syscall
* @features: bit mask see UFFD_API_FEATURES
*/
static bool request_ufd_features(int ufd, uint64_t features)
{
struct uffdio_api api_struct = {0};
uint64_t ioctl_mask;
api_struct.api = UFFD_API;
api_struct.features = features;
if (ioctl(ufd, UFFDIO_API, &api_struct)) {
error_report("%s failed: UFFDIO_API failed: %s", __func__,
strerror(errno));
return false;
}
ioctl_mask = (__u64)1 << _UFFDIO_REGISTER |
(__u64)1 << _UFFDIO_UNREGISTER;
if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) {
error_report("Missing userfault features: %" PRIx64,
(uint64_t)(~api_struct.ioctls & ioctl_mask));
return false;
}
return true;
}
static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis)
{
uint64_t asked_features = 0;
static uint64_t supported_features;
/*
* it's not possible to
* request UFFD_API twice per one fd
* userfault fd features is persistent
*/
if (!supported_features) {
if (!receive_ufd_features(&supported_features)) {
error_report("%s failed", __func__);
return false;
}
}
/*
* request features, even if asked_features is 0, due to
* kernel expects UFFD_API before UFFDIO_REGISTER, per
* userfault file descriptor
*/
if (!request_ufd_features(ufd, asked_features)) {
error_report("%s failed: features %" PRIu64, __func__,
asked_features);
return false;
}
if (getpagesize() != ram_pagesize_summary()) {
bool have_hp = false;
/* We've got a huge page */
#ifdef UFFD_FEATURE_MISSING_HUGETLBFS
have_hp = supported_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_ramblock_postcopiable(const char *block_name, void *host_addr,
ram_addr_t offset, ram_addr_t length, void *opaque)
{
RAMBlock *rb = qemu_ram_block_by_name(block_name);
size_t pagesize = qemu_ram_pagesize(rb);
if (length % pagesize) {
error_report("Postcopy requires RAM blocks to be a page size multiple,"
" block %s is 0x" RAM_ADDR_FMT " bytes with a "
"page size of 0x%zx", block_name, length, pagesize);
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(MigrationIncomingState *mis)
{
long pagesize = getpagesize();
int ufd = -1;
bool ret = false; /* Error unless we change it */
void *testarea = NULL;
struct uffdio_register reg_struct;
struct uffdio_range range_struct;
uint64_t feature_mask;
Error *local_err = NULL;
if (qemu_target_page_size() > pagesize) {
error_report("Target page size bigger than host page size");
goto out;
}
ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
if (ufd == -1) {
error_report("%s: userfaultfd not available: %s", __func__,
strerror(errno));
goto out;
}
/* Give devices a chance to object */
if (postcopy_notify(POSTCOPY_NOTIFY_PROBE, &local_err)) {
error_report_err(local_err);
goto out;
}
/* Version and features check */
if (!ufd_check_and_apply(ufd, mis)) {
goto out;
}
/* We don't support postcopy with shared RAM yet */
if (qemu_ram_foreach_block(test_ramblock_postcopiable, 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
* are returned.
*/
testarea = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE |
MAP_ANONYMOUS, -1, 0);
if (testarea == MAP_FAILED) {
error_report("%s: Failed to map test area: %s", __func__,
strerror(errno));
goto out;
}
g_assert(((size_t)testarea & (pagesize-1)) == 0);
reg_struct.range.start = (uintptr_t)testarea;
reg_struct.range.len = pagesize;
reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
if (ioctl(ufd, UFFDIO_REGISTER, &reg_struct)) {
error_report("%s userfault register: %s", __func__, strerror(errno));
goto out;
}
range_struct.start = (uintptr_t)testarea;
range_struct.len = pagesize;
if (ioctl(ufd, UFFDIO_UNREGISTER, &range_struct)) {
error_report("%s userfault unregister: %s", __func__, strerror(errno));
goto out;
}
feature_mask = (__u64)1 << _UFFDIO_WAKE |
(__u64)1 << _UFFDIO_COPY |
(__u64)1 << _UFFDIO_ZEROPAGE;
if ((reg_struct.ioctls & feature_mask) != feature_mask) {
error_report("Missing userfault map features: %" PRIx64,
(uint64_t)(~reg_struct.ioctls & feature_mask));
goto out;
}
/* Success! */
ret = true;
out:
if (testarea) {
munmap(testarea, pagesize);
}
if (ufd != -1) {
close(ufd);
}
return ret;
}
/*
* 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.
* opaque should be the MIS.
*/
static int init_range(const char *block_name, void *host_addr,
ram_addr_t offset, ram_addr_t length, void *opaque)
{
trace_postcopy_init_range(block_name, host_addr, offset, length);
/*
* We need the whole of RAM to be truly empty for postcopy, so things
* like ROMs and any data tables built during init must be zero'd
* - we're going to get the copy from the source anyway.
* (Precopy will just overwrite this data, so doesn't need the discard)
*/
if (ram_discard_range(block_name, 0, length)) {
return -1;
}
return 0;
}
/*
* At the end of migration, undo the effects of init_range
* opaque should be the MIS.
*/
static int cleanup_range(const char *block_name, void *host_addr,
ram_addr_t offset, ram_addr_t length, void *opaque)
{
MigrationIncomingState *mis = opaque;
struct uffdio_range range_struct;
trace_postcopy_cleanup_range(block_name, host_addr, offset, length);
/*
* We turned off hugepage for the precopy stage with postcopy enabled
* we can turn it back on now.
*/
qemu_madvise(host_addr, length, QEMU_MADV_HUGEPAGE);
/*
* We can also turn off userfault now since we should have all the
* pages. It can be useful to leave it on to debug postcopy
* if you're not sure it's always getting every page.
*/
range_struct.start = (uintptr_t)host_addr;
range_struct.len = length;
if (ioctl(mis->userfault_fd, UFFDIO_UNREGISTER, &range_struct)) {
error_report("%s: userfault unregister %s", __func__, strerror(errno));
return -1;
}
return 0;
}
/*
* Initialise postcopy-ram, setting the RAM to a state where we can go into
* postcopy later; must be called prior to any precopy.
* called from arch_init's similarly named ram_postcopy_incoming_init
*/
int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages)
{
if (qemu_ram_foreach_block(init_range, NULL)) {
return -1;
}
return 0;
}
/*
* At the end of a migration where postcopy_ram_incoming_init was called.
*/
int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
{
trace_postcopy_ram_incoming_cleanup_entry();
if (mis->have_fault_thread) {
Error *local_err = NULL;
if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_END, &local_err)) {
error_report_err(local_err);
return -1;
}
if (qemu_ram_foreach_block(cleanup_range, mis)) {
return -1;
}
/* Let the fault thread quit */
atomic_set(&mis->fault_thread_quit, 1);
postcopy_fault_thread_notify(mis);
trace_postcopy_ram_incoming_cleanup_join();
qemu_thread_join(&mis->fault_thread);
trace_postcopy_ram_incoming_cleanup_closeuf();
close(mis->userfault_fd);
close(mis->userfault_event_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);
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;
}
/*
* Mark the given area of RAM as requiring notification to unwritten areas
* Used as a callback on qemu_ram_foreach_block.
* host_addr: Base of area to mark
* offset: Offset in the whole ram arena
* length: Length of the section
* opaque: MigrationIncomingState pointer
* Returns 0 on success
*/
static int ram_block_enable_notify(const char *block_name, void *host_addr,
ram_addr_t offset, ram_addr_t length,
void *opaque)
{
MigrationIncomingState *mis = opaque;
struct uffdio_register reg_struct;
reg_struct.range.start = (uintptr_t)host_addr;
reg_struct.range.len = length;
reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
/* Now tell our userfault_fd that it's responsible for this area */
if (ioctl(mis->userfault_fd, UFFDIO_REGISTER, &reg_struct)) {
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;
}
if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) {
RAMBlock *rb = qemu_ram_block_by_name(block_name);
qemu_ram_set_uf_zeroable(rb);
}
return 0;
}
int postcopy_wake_shared(struct PostCopyFD *pcfd,
uint64_t client_addr,
RAMBlock *rb)
{
size_t pagesize = qemu_ram_pagesize(rb);
struct uffdio_range range;
int ret;
trace_postcopy_wake_shared(client_addr, qemu_ram_get_idstr(rb));
range.start = client_addr & ~(pagesize - 1);
range.len = pagesize;
ret = ioctl(pcfd->fd, UFFDIO_WAKE, &range);
if (ret) {
error_report("%s: Failed to wake: %zx in %s (%s)",
__func__, (size_t)client_addr, qemu_ram_get_idstr(rb),
strerror(errno));
}
return ret;
}
/*
* Callback from shared fault handlers to ask for a page,
* the page must be specified by a RAMBlock and an offset in that rb
* Note: Only for use by shared fault handlers (in fault thread)
*/
int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
uint64_t client_addr, uint64_t rb_offset)
{
size_t pagesize = qemu_ram_pagesize(rb);
uint64_t aligned_rbo = rb_offset & ~(pagesize - 1);
MigrationIncomingState *mis = migration_incoming_get_current();
trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb),
rb_offset);
if (ramblock_recv_bitmap_test_byte_offset(rb, aligned_rbo)) {
trace_postcopy_request_shared_page_present(pcfd->idstr,
qemu_ram_get_idstr(rb), rb_offset);
return postcopy_wake_shared(pcfd, client_addr, rb);
}
if (rb != mis->last_rb) {
mis->last_rb = rb;
migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
aligned_rbo, pagesize);
} else {
/* Save some space */
migrate_send_rp_req_pages(mis, NULL, aligned_rbo, pagesize);
}
return 0;
}
/*
* Handle faults detected by the USERFAULT markings
*/
static void *postcopy_ram_fault_thread(void *opaque)
{
MigrationIncomingState *mis = opaque;
struct uffd_msg msg;
int ret;
size_t index;
RAMBlock *rb = NULL;
trace_postcopy_ram_fault_thread_entry();
mis->last_rb = NULL; /* last RAMBlock we sent part of */
qemu_sem_post(&mis->fault_thread_sem);
struct pollfd *pfd;
size_t pfd_len = 2 + mis->postcopy_remote_fds->len;
pfd = g_new0(struct pollfd, pfd_len);
pfd[0].fd = mis->userfault_fd;
pfd[0].events = POLLIN;
pfd[1].fd = mis->userfault_event_fd;
pfd[1].events = POLLIN; /* Waiting for eventfd to go positive */
trace_postcopy_ram_fault_thread_fds_core(pfd[0].fd, pfd[1].fd);
for (index = 0; index < mis->postcopy_remote_fds->len; index++) {
struct PostCopyFD *pcfd = &g_array_index(mis->postcopy_remote_fds,
struct PostCopyFD, index);
pfd[2 + index].fd = pcfd->fd;
pfd[2 + index].events = POLLIN;
trace_postcopy_ram_fault_thread_fds_extra(2 + index, pcfd->idstr,
pcfd->fd);
}
while (true) {
ram_addr_t rb_offset;
int poll_result;
/*
* 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
*/
poll_result = poll(pfd, pfd_len, -1 /* Wait forever */);
if (poll_result == -1) {
error_report("%s: userfault poll: %s", __func__, strerror(errno));
break;
}
if (pfd[1].revents) {
uint64_t tmp64 = 0;
/* Consume the signal */
if (read(mis->userfault_event_fd, &tmp64, 8) != 8) {
/* Nothing obviously nicer than posting this error. */
error_report("%s: read() failed", __func__);
}
if (atomic_read(&mis->fault_thread_quit)) {
trace_postcopy_ram_fault_thread_quit();
break;
}
}
if (pfd[0].revents) {
poll_result--;
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 != mis->last_rb) {
mis->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));
}
}
/* Now handle any requests from external processes on shared memory */
/* TODO: May need to handle devices deregistering during postcopy */
for (index = 2; index < pfd_len && poll_result; index++) {
if (pfd[index].revents) {
struct PostCopyFD *pcfd =
&g_array_index(mis->postcopy_remote_fds,
struct PostCopyFD, index - 2);
poll_result--;
if (pfd[index].revents & POLLERR) {
error_report("%s: POLLERR on poll %zd fd=%d",
__func__, index, pcfd->fd);
pfd[index].events = 0;
continue;
}
ret = read(pcfd->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 (shared) revents=%d",
__func__, strerror(errno),
pfd[index].revents);
/*TODO: Could just disable this sharer */
break;
} else {
error_report("%s: Read %d bytes from userfaultfd "
"expected %zd (shared)",
__func__, ret, sizeof(msg));
/*TODO: Could just disable this sharer */
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 (shared)",
__func__, msg.event);
continue; /* It's not a page fault, shouldn't happen */
}
/* Call the device handler registered with us */
ret = pcfd->handler(pcfd, &msg);
if (ret) {
error_report("%s: Failed to resolve shared fault on %zd/%s",
__func__, index, pcfd->idstr);
/* TODO: Fail? Disable this sharer? */
}
}
}
}
trace_postcopy_ram_fault_thread_exit();
return NULL;
}
int postcopy_ram_enable_notify(MigrationIncomingState *mis)
{
/* 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_check_and_apply(mis->userfault_fd, mis)) {
return -1;
}
/* Now an eventfd we use to tell the fault-thread to quit */
mis->userfault_event_fd = eventfd(0, EFD_CLOEXEC);
if (mis->userfault_event_fd == -1) {
error_report("%s: Opening userfault_event_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;
}
static int qemu_ufd_copy_ioctl(int userfault_fd, void *host_addr,
void *from_addr, uint64_t pagesize, RAMBlock *rb)
{
int ret;
if (from_addr) {
struct uffdio_copy copy_struct;
copy_struct.dst = (uint64_t)(uintptr_t)host_addr;
copy_struct.src = (uint64_t)(uintptr_t)from_addr;
copy_struct.len = pagesize;
copy_struct.mode = 0;
ret = ioctl(userfault_fd, UFFDIO_COPY, &copy_struct);
} else {
struct uffdio_zeropage zero_struct;
zero_struct.range.start = (uint64_t)(uintptr_t)host_addr;
zero_struct.range.len = pagesize;
zero_struct.mode = 0;
ret = ioctl(userfault_fd, UFFDIO_ZEROPAGE, &zero_struct);
}
if (!ret) {
ramblock_recv_bitmap_set_range(rb, host_addr,
pagesize / qemu_target_page_size());
}
return ret;
}
int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset)
{
int i;
MigrationIncomingState *mis = migration_incoming_get_current();
GArray *pcrfds = mis->postcopy_remote_fds;
for (i = 0; i < pcrfds->len; i++) {
struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i);
int ret = cur->waker(cur, rb, offset);
if (ret) {
return ret;
}
}
return 0;
}
/*
* Place a host page (from) at (host) atomically
* returns 0 on success
*/
int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
RAMBlock *rb)
{
size_t pagesize = qemu_ram_pagesize(rb);
/* 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 (qemu_ufd_copy_ioctl(mis->userfault_fd, host, from, pagesize, rb)) {
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 postcopy_notify_shared_wake(rb,
qemu_ram_block_host_offset(rb, host));
}
/*
* Place a zero page at (host) atomically
* returns 0 on success
*/
int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
RAMBlock *rb)
{
size_t pagesize = qemu_ram_pagesize(rb);
trace_postcopy_place_page_zero(host);
/* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE
* but it's not available for everything (e.g. hugetlbpages)
*/
if (qemu_ram_is_uf_zeroable(rb)) {
if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize, rb)) {
int e = errno;
error_report("%s: %s zero host: %p",
__func__, strerror(e), host);
return -e;
}
return postcopy_notify_shared_wake(rb,
qemu_ram_block_host_offset(rb,
host));
} 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,
rb);
}
}
/*
* 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(MigrationIncomingState *mis)
{
error_report("%s: No OS support", __func__);
return false;
}
int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages)
{
error_report("postcopy_ram_incoming_init: No OS support");
return -1;
}
int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
{
assert(0);
return -1;
}
int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
{
assert(0);
return -1;
}
int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
uint64_t client_addr, uint64_t rb_offset)
{
assert(0);
return -1;
}
int postcopy_ram_enable_notify(MigrationIncomingState *mis)
{
assert(0);
return -1;
}
int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
RAMBlock *rb)
{
assert(0);
return -1;
}
int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
RAMBlock *rb)
{
assert(0);
return -1;
}
void *postcopy_get_tmp_page(MigrationIncomingState *mis)
{
assert(0);
return NULL;
}
int postcopy_wake_shared(struct PostCopyFD *pcfd,
uint64_t client_addr,
RAMBlock *rb)
{
assert(0);
return -1;
}
#endif
/* ------------------------------------------------------------------------- */
void postcopy_fault_thread_notify(MigrationIncomingState *mis)
{
uint64_t tmp64 = 1;
/*
* Wakeup the fault_thread. It's an eventfd that should currently
* be at 0, we're going to increment it to 1
*/
if (write(mis->userfault_event_fd, &tmp64, 8) != 8) {
/* Not much we can do here, but may as well report it */
error_report("%s: incrementing failed: %s", __func__,
strerror(errno));
}
}
/**
* postcopy_discard_send_init: Called at the start of each RAMBlock before
* asking to discard individual ranges.
*
* @ms: The current migration state.
* @offset: the bitmap offset of the named RAMBlock in the migration
* bitmap.
* @name: RAMBlock that discards will operate on.
*
* returns: a new PDS.
*/
PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
const char *name)
{
PostcopyDiscardState *res = g_malloc0(sizeof(PostcopyDiscardState));
if (res) {
res->ramblock_name = name;
}
return res;
}
/**
* postcopy_discard_send_range: Called by the bitmap code for each chunk to
* discard. May send a discard message, may just leave it queued to
* be sent later.
*
* @ms: Current migration state.
* @pds: Structure initialised by postcopy_discard_send_init().
* @start,@length: a range of pages in the migration bitmap in the
* RAM block passed to postcopy_discard_send_init() (length=1 is one page)
*/
void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds,
unsigned long start, unsigned long length)
{
size_t tp_size = qemu_target_page_size();
/* Convert to byte offsets within the RAM block */
pds->start_list[pds->cur_entry] = start * tp_size;
pds->length_list[pds->cur_entry] = length * tp_size;
trace_postcopy_discard_send_range(pds->ramblock_name, start, length);
pds->cur_entry++;
pds->nsentwords++;
if (pds->cur_entry == MAX_DISCARDS_PER_COMMAND) {
/* Full set, ship it! */
qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
pds->ramblock_name,
pds->cur_entry,
pds->start_list,
pds->length_list);
pds->nsentcmds++;
pds->cur_entry = 0;
}
}
/**
* postcopy_discard_send_finish: Called at the end of each RAMBlock by the
* bitmap code. Sends any outstanding discard messages, frees the PDS
*
* @ms: Current migration state.
* @pds: Structure initialised by postcopy_discard_send_init().
*/
void postcopy_discard_send_finish(MigrationState *ms, PostcopyDiscardState *pds)
{
/* Anything unsent? */
if (pds->cur_entry) {
qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
pds->ramblock_name,
pds->cur_entry,
pds->start_list,
pds->length_list);
pds->nsentcmds++;
}
trace_postcopy_discard_send_finish(pds->ramblock_name, pds->nsentwords,
pds->nsentcmds);
g_free(pds);
}
/*
* Current state of incoming postcopy; note this is not part of
* MigrationIncomingState since it's state is used during cleanup
* at the end as MIS is being freed.
*/
static PostcopyState incoming_postcopy_state;
PostcopyState postcopy_state_get(void)
{
return atomic_mb_read(&incoming_postcopy_state);
}
/* Set the state and return the old state */
PostcopyState postcopy_state_set(PostcopyState new_state)
{
return atomic_xchg(&incoming_postcopy_state, new_state);
}
/* Register a handler for external shared memory postcopy
* called on the destination.
*/
void postcopy_register_shared_ufd(struct PostCopyFD *pcfd)
{
MigrationIncomingState *mis = migration_incoming_get_current();
mis->postcopy_remote_fds = g_array_append_val(mis->postcopy_remote_fds,
*pcfd);
}
/* Unregister a handler for external shared memory postcopy
*/
void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd)
{
guint i;
MigrationIncomingState *mis = migration_incoming_get_current();
GArray *pcrfds = mis->postcopy_remote_fds;
for (i = 0; i < pcrfds->len; i++) {
struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i);
if (cur->fd == pcfd->fd) {
mis->postcopy_remote_fds = g_array_remove_index(pcrfds, i);
return;
}
}
}
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