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Migration pull request

Browse Source 
- Ani's patch to complete the memory API on coalesced IO / eventfd notifies
 - Fabiano's Coverity fix on using pstrcpy() over strncpy()
 - Dave's series on removing/deprecating zero-blocks and uffd cleanups
 - Juraj's one more fix on multifd/cancel test where it can fail when
   cancellation happens too slow on src
 - Dave's one more remove deadcode patch in iova-tree.c
 - Yuan's build fix for multifd qpl compressor
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 HMxp8A2jeYsBAK+d5lYGX1V2FtQ152YiOJQzRW31MkdAOishJzcHCXgO
 =gBW0
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Merge tag 'migration-20241009-pull-request' of https://gitlab.com/peterx/qemu into staging

Migration pull request

- Ani's patch to complete the memory API on coalesced IO / eventfd notifies
- Fabiano's Coverity fix on using pstrcpy() over strncpy()
- Dave's series on removing/deprecating zero-blocks and uffd cleanups
- Juraj's one more fix on multifd/cancel test where it can fail when
  cancellation happens too slow on src
- Dave's one more remove deadcode patch in iova-tree.c
- Yuan's build fix for multifd qpl compressor

# -----BEGIN PGP SIGNATURE-----
#
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# ZGhhdC5jb20ACgkQO1/MzfOr1wa3ZwD9HiAN9m7WOfZxXKOVIIwhOjUNTw0FiFeO
# HMxp8A2jeYsBAK+d5lYGX1V2FtQ152YiOJQzRW31MkdAOishJzcHCXgO
# =gBW0
# -----END PGP SIGNATURE-----
# gpg: Signature made Wed 09 Oct 2024 13:41:44 BST
# gpg:                using EDDSA key B9184DC20CC457DACF7DD1A93B5FCCCDF3ABD706
# gpg:                issuer "peterx@redhat.com"
# gpg: Good signature from "Peter Xu <xzpeter@gmail.com>" [marginal]
# gpg:                 aka "Peter Xu <peterx@redhat.com>" [marginal]
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: B918 4DC2 0CC4 57DA CF7D  D1A9 3B5F CCCD F3AB D706

* tag 'migration-20241009-pull-request' of https://gitlab.com/peterx/qemu:
  migration/multifd: fix build error when qpl compression is enabled
  util/iova-tree: Remove deadcode
  tests/migration-test: Wait for cancellation sooner in multifd cancel
  util/userfaultfd: Remove unused uffd_poll_events
  migration/postcopy: Use uffd helpers
  util/userfaultfd: Return -errno on error
  migration: Remove unused socket_send_channel_create_sync
  migration: Deprecate zero-blocks capability
  migration: Remove unused migrate_zero_blocks
  migration: Remove migrate_cap_set
  migration/multifd: Ensure packet->ramblock is null-terminated
  memory: notify hypervisor of all eventfds during listener (de)registration

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Peter Maydell 2024-10-09 20:12:11 +01:00
commit 05adb38839
15 changed files with 141 additions and 177 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
docs/about/deprecated.rst
View File

@ -473,3 +473,9 @@ usage of providing a file descriptor to a plain file has been
deprecated in favor of explicitly using the ``file:`` URI with the
file descriptor being passed as an ``fdset``. Refer to the ``add-fd``
command documentation for details on the ``fdset`` usage.
``zero-blocks`` capability (since 9.2)
''''''''''''''''''''''''''''''''''''''
The ``zero-blocks`` capability was part of the block migration which
doesn't exist anymore since it was removed in QEMU v9.1.

25
include/qemu/iova-tree.h
View File

@ -111,31 +111,6 @@ const DMAMap *iova_tree_find(const IOVATree *tree, const DMAMap *map);
*/
const DMAMap *iova_tree_find_iova(const IOVATree *tree, const DMAMap *map);
/**
* iova_tree_find_address:
*
* @tree: the iova tree to search from
* @iova: the iova address to find
*
* Similar to iova_tree_find(), but it tries to find mapping with
* range iova=iova & size=0.
*
* Return: same as iova_tree_find().
*/
const DMAMap *iova_tree_find_address(const IOVATree *tree, hwaddr iova);
/**
* iova_tree_foreach:
*
* @tree: the iova tree to iterate on
* @iterator: the iterator for the mappings, return true to stop
*
* Iterate over the iova tree.
*
* Return: 1 if found any overlap, 0 if not, <0 if error.
*/
void iova_tree_foreach(IOVATree *tree, iova_tree_iterator iterator);
/**
* iova_tree_alloc_map:
*

1
include/qemu/userfaultfd.h
View File

@ -39,7 +39,6 @@ int uffd_copy_page(int uffd_fd, void *dst_addr, void *src_addr,
int uffd_zero_page(int uffd_fd, void *addr, uint64_t length, bool dont_wake);
int uffd_wakeup(int uffd_fd, void *addr, uint64_t length);
int uffd_read_events(int uffd_fd, struct uffd_msg *msgs, int count);
bool uffd_poll_events(int uffd_fd, int tmo);
#endif /* CONFIG_LINUX */

4
migration/multifd-nocomp.c
View File

@ -17,6 +17,7 @@
#include "multifd.h"
#include "options.h"
#include "qapi/error.h"
#include "qemu/cutils.h"
#include "qemu/error-report.h"
#include "trace.h"
@ -201,7 +202,8 @@ void multifd_ram_fill_packet(MultiFDSendParams *p)
packet->zero_pages = cpu_to_be32(zero_num);
if (pages->block) {
strncpy(packet->ramblock, pages->block->idstr, 256);
pstrcpy(packet->ramblock, sizeof(packet->ramblock),
pages->block->idstr);
}
for (int i = 0; i < pages->num; i++) {

10
migration/multifd-qpl.c
View File

@ -389,7 +389,7 @@ static void multifd_qpl_compress_pages_slow_path(MultiFDSendParams *p)
{
QplData *qpl = p->compress_data;
MultiFDPages_t *pages = &p->data->u.ram;
uint32_t size = p->page_size;
uint32_t size = multifd_ram_page_size();
qpl_job *job = qpl->sw_job;
uint8_t *zbuf = qpl->zbuf;
uint8_t *buf;
@ -420,7 +420,7 @@ static void multifd_qpl_compress_pages(MultiFDSendParams *p)
{
QplData *qpl = p->compress_data;
MultiFDPages_t *pages = &p->data->u.ram;
uint32_t size = p->page_size;
uint32_t size = multifd_ram_page_size();
QplHwJob *hw_job;
uint8_t *buf;
uint8_t *zbuf;
@ -560,7 +560,7 @@ static int multifd_qpl_decompress_pages_slow_path(MultiFDRecvParams *p,
Error **errp)
{
QplData *qpl = p->compress_data;
uint32_t size = p->page_size;
uint32_t size = multifd_ram_page_size();
qpl_job *job = qpl->sw_job;
uint8_t *zbuf = qpl->zbuf;
uint8_t *addr;
@ -598,7 +598,7 @@ static int multifd_qpl_decompress_pages_slow_path(MultiFDRecvParams *p,
static int multifd_qpl_decompress_pages(MultiFDRecvParams *p, Error **errp)
{
QplData *qpl = p->compress_data;
uint32_t size = p->page_size;
uint32_t size = multifd_ram_page_size();
uint8_t *zbuf = qpl->zbuf;
uint8_t *addr;
uint32_t len;
@ -677,7 +677,7 @@ static int multifd_qpl_recv(MultiFDRecvParams *p, Error **errp)
}
for (int i = 0; i < p->normal_num; i++) {
qpl->zlen[i] = be32_to_cpu(qpl->zlen[i]);
assert(qpl->zlen[i] <= p->page_size);
assert(qpl->zlen[i] <= multifd_ram_page_size());
zbuf_len += qpl->zlen[i];
}

31
migration/options.c
View File

@ -339,13 +339,6 @@ bool migrate_xbzrle(void)
return s->capabilities[MIGRATION_CAPABILITY_XBZRLE];
}
bool migrate_zero_blocks(void)
{
MigrationState *s = migrate_get_current();
return s->capabilities[MIGRATION_CAPABILITY_ZERO_BLOCKS];
}
bool migrate_zero_copy_send(void)
{
MigrationState *s = migrate_get_current();
@ -457,6 +450,10 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
ERRP_GUARD();
MigrationIncomingState *mis = migration_incoming_get_current();
if (new_caps[MIGRATION_CAPABILITY_ZERO_BLOCKS]) {
warn_report("zero-blocks capability is deprecated");
}
#ifndef CONFIG_REPLICATION
if (new_caps[MIGRATION_CAPABILITY_X_COLO]) {
error_setg(errp, "QEMU compiled without replication module"
@ -605,26 +602,6 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
return true;
}
bool migrate_cap_set(int cap, bool value, Error **errp)
{
MigrationState *s = migrate_get_current();
bool new_caps[MIGRATION_CAPABILITY__MAX];
if (migration_is_running()) {
error_setg(errp, "There's a migration process in progress");
return false;
}
memcpy(new_caps, s->capabilities, sizeof(new_caps));
new_caps[cap] = value;
if (!migrate_caps_check(s->capabilities, new_caps, errp)) {
return false;
}
s->capabilities[cap] = value;
return true;
}
MigrationCapabilityStatusList *qmp_query_migrate_capabilities(Error **errp)
{
MigrationCapabilityStatusList *head = NULL, **tail = &head;

2
migration/options.h
View File

@ -40,7 +40,6 @@ bool migrate_release_ram(void);
bool migrate_return_path(void);
bool migrate_validate_uuid(void);
bool migrate_xbzrle(void);
bool migrate_zero_blocks(void);
bool migrate_zero_copy_send(void);
/*
@ -58,7 +57,6 @@ bool migrate_tls(void);
/* capabilities helpers */
bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp);
bool migrate_cap_set(int cap, bool value, Error **errp);
/* parameters */

48
migration/postcopy-ram.c
View File

@ -746,18 +746,10 @@ int postcopy_wake_shared(struct PostCopyFD *pcfd,
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 = ROUND_DOWN(client_addr, pagesize);
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;
return uffd_wakeup(pcfd->fd,
(void *)(uintptr_t)ROUND_DOWN(client_addr, pagesize),
pagesize);
}
static int postcopy_request_page(MigrationIncomingState *mis, RAMBlock *rb,
@ -1275,18 +1267,10 @@ static int qemu_ufd_copy_ioctl(MigrationIncomingState *mis, void *host_addr,
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);
ret = uffd_copy_page(userfault_fd, host_addr, from_addr, pagesize,
false);
} 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);
ret = uffd_zero_page(userfault_fd, host_addr, pagesize, false);
}
if (!ret) {
qemu_mutex_lock(&mis->page_request_mutex);
@ -1343,18 +1327,16 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
RAMBlock *rb)
{
size_t pagesize = qemu_ram_pagesize(rb);
int e;
/* 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, 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;
e = qemu_ufd_copy_ioctl(mis, host, from, pagesize, rb);
if (e) {
return e;
}
trace_postcopy_place_page(host);
@ -1376,12 +1358,10 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
* but it's not available for everything (e.g. hugetlbpages)
*/
if (qemu_ram_is_uf_zeroable(rb)) {
if (qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb)) {
int e = errno;
error_report("%s: %s zero host: %p",
__func__, strerror(e), host);
return -e;
int e;
e = qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb);
if (e) {
return e;
}
return postcopy_notify_shared_wake(rb,
qemu_ram_block_host_offset(rb,

18
migration/socket.c
View File

@ -42,24 +42,6 @@ void socket_send_channel_create(QIOTaskFunc f, void *data)
f, data, NULL, NULL);
}
QIOChannel *socket_send_channel_create_sync(Error **errp)
{
QIOChannelSocket *sioc = qio_channel_socket_new();
if (!outgoing_args.saddr) {
object_unref(OBJECT(sioc));
error_setg(errp, "Initial sock address not set!");
return NULL;
}
if (qio_channel_socket_connect_sync(sioc, outgoing_args.saddr, errp) < 0) {
object_unref(OBJECT(sioc));
return NULL;
}
return QIO_CHANNEL(sioc);
}
struct SocketConnectData {
MigrationState *s;
char *hostname;

1
migration/socket.h
View File

@ -22,7 +22,6 @@
#include "qemu/sockets.h"
void socket_send_channel_create(QIOTaskFunc f, void *data);
QIOChannel *socket_send_channel_create_sync(Error **errp);
void socket_start_incoming_migration(SocketAddress *saddr, Error **errp);

5
qapi/migration.json
View File

@ -479,11 +479,14 @@
# Features:
#
# @unstable: Members @x-colo and @x-ignore-shared are experimental.
# @deprecated: Member @zero-blocks is deprecated as being part of
# block migration which was already removed.
#
# Since: 1.2
##
{ 'enum': 'MigrationCapability',
'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
'data': ['xbzrle', 'rdma-pin-all', 'auto-converge',
{ 'name': 'zero-blocks', 'features': [ 'deprecated' ] },
'events', 'postcopy-ram',
{ 'name': 'x-colo', 'features': [ 'unstable' ] },
'release-ram',

83
system/memory.c
View File

@ -941,6 +941,38 @@ static void flat_range_coalesced_io_add(FlatRange *fr, AddressSpace *as)
}
}
static void
flat_range_coalesced_io_notify_listener_add_del(FlatRange *fr,
MemoryRegionSection *mrs,
MemoryListener *listener,
AddressSpace *as, bool add)
{
CoalescedMemoryRange *cmr;
MemoryRegion *mr = fr->mr;
AddrRange tmp;
QTAILQ_FOREACH(cmr, &mr->coalesced, link) {
tmp = addrrange_shift(cmr->addr,
int128_sub(fr->addr.start,
int128_make64(fr->offset_in_region)));
if (!addrrange_intersects(tmp, fr->addr)) {
return;
}
tmp = addrrange_intersection(tmp, fr->addr);
if (add && listener->coalesced_io_add) {
listener->coalesced_io_add(listener, mrs,
int128_get64(tmp.start),
int128_get64(tmp.size));
} else if (!add && listener->coalesced_io_del) {
listener->coalesced_io_del(listener, mrs,
int128_get64(tmp.start),
int128_get64(tmp.size));
}
}
}
static void address_space_update_topology_pass(AddressSpace *as,
const FlatView *old_view,
const FlatView *new_view,
@ -3015,8 +3047,10 @@ void memory_global_dirty_log_stop(unsigned int flags)
static void listener_add_address_space(MemoryListener *listener,
AddressSpace *as)
{
unsigned i;
FlatView *view;
FlatRange *fr;
MemoryRegionIoeventfd *fd;
if (listener->begin) {
listener->begin(listener);
@ -3041,10 +3075,34 @@ static void listener_add_address_space(MemoryListener *listener,
if (listener->region_add) {
listener->region_add(listener, &section);
}
/* send coalesced io add notifications */
flat_range_coalesced_io_notify_listener_add_del(fr, &section,
listener, as, true);
if (fr->dirty_log_mask && listener->log_start) {
listener->log_start(listener, &section, 0, fr->dirty_log_mask);
}
}
/*
* register all eventfds for this address space for the newly registered
* listener.
*/
for (i = 0; i < as->ioeventfd_nb; i++) {
fd = &as->ioeventfds[i];
MemoryRegionSection section = (MemoryRegionSection) {
.fv = view,
.offset_within_address_space = int128_get64(fd->addr.start),
.size = fd->addr.size,
};
if (listener->eventfd_add) {
listener->eventfd_add(listener, &section,
fd->match_data, fd->data, fd->e);
}
}
if (listener->commit) {
listener->commit(listener);
}
@ -3054,8 +3112,10 @@ static void listener_add_address_space(MemoryListener *listener,
static void listener_del_address_space(MemoryListener *listener,
AddressSpace *as)
{
unsigned i;
FlatView *view;
FlatRange *fr;
MemoryRegionIoeventfd *fd;
if (listener->begin) {
listener->begin(listener);
@ -3067,10 +3127,33 @@ static void listener_del_address_space(MemoryListener *listener,
if (fr->dirty_log_mask && listener->log_stop) {
listener->log_stop(listener, &section, fr->dirty_log_mask, 0);
}
/* send coalesced io del notifications */
flat_range_coalesced_io_notify_listener_add_del(fr, &section,
listener, as, false);
if (listener->region_del) {
listener->region_del(listener, &section);
}
}
/*
* de-register all eventfds for this address space for the current
* listener.
*/
for (i = 0; i < as->ioeventfd_nb; i++) {
fd = &as->ioeventfds[i];
MemoryRegionSection section = (MemoryRegionSection) {
.fv = view,
.offset_within_address_space = int128_get64(fd->addr.start),
.size = fd->addr.size,
};
if (listener->eventfd_del) {
listener->eventfd_del(listener, &section,
fd->match_data, fd->data, fd->e);
}
}
if (listener->commit) {
listener->commit(listener);
}

12
tests/qtest/migration-test.c
View File

@ -3267,6 +3267,16 @@ static void test_multifd_tcp_cancel(void)
qtest_wait_qemu(to);
qtest_quit(to);
/*
* Ensure the source QEMU finishes its cancellation process before we
* proceed with the setup of the next migration. The test_migrate_start()
* function and others might want to interact with the source in a way that
* is not possible while the migration is not canceled properly. For
* example, setting migration capabilities when the migration is still
* running leads to an error.
*/
wait_for_migration_status(from, "cancelled", NULL);
args = (MigrateStart){
.only_target = true,
};
@ -3282,8 +3292,6 @@ static void test_multifd_tcp_cancel(void)
/* Start incoming migration from the 1st socket */
migrate_incoming_qmp(to2, "tcp:127.0.0.1:0", "{}");
wait_for_migration_status(from, "cancelled", NULL);
migrate_ensure_non_converge(from);
migrate_qmp(from, to2, NULL, NULL, "{}");

23
util/iova-tree.c
View File

@ -115,13 +115,6 @@ const DMAMap *iova_tree_find_iova(const IOVATree *tree, const DMAMap *map)
return args.result;
}
const DMAMap *iova_tree_find_address(const IOVATree *tree, hwaddr iova)
{
const DMAMap map = { .iova = iova, .size = 0 };
return iova_tree_find(tree, &map);
}
static inline void iova_tree_insert_internal(GTree *gtree, DMAMap *range)
{
/* Key and value are sharing the same range data */
@ -148,22 +141,6 @@ int iova_tree_insert(IOVATree *tree, const DMAMap *map)
return IOVA_OK;
}
static gboolean iova_tree_traverse(gpointer key, gpointer value,
gpointer data)
{
iova_tree_iterator iterator = data;
DMAMap *map = key;
g_assert(key == value);
return iterator(map);
}
void iova_tree_foreach(IOVATree *tree, iova_tree_iterator iterator)
{
g_tree_foreach(tree->tree, iova_tree_traverse, iterator);
}
void iova_tree_remove(IOVATree *tree, DMAMap map)
{
const DMAMap *overlap;

49
util/userfaultfd.c
View File

@ -240,7 +240,7 @@ int uffd_change_protection(int uffd_fd, void *addr, uint64_t length,
* Copy range of source pages to the destination to resolve
* missing page fault somewhere in the destination range.
*
* Returns 0 on success, negative value in case of an error
* Returns 0 on success, -errno in case of an error
*
* @uffd_fd: UFFD file descriptor
* @dst_addr: destination base address
@ -259,10 +259,11 @@ int uffd_copy_page(int uffd_fd, void *dst_addr, void *src_addr,
uffd_copy.mode = dont_wake ? UFFDIO_COPY_MODE_DONTWAKE : 0;
if (ioctl(uffd_fd, UFFDIO_COPY, &uffd_copy)) {
int e = errno;
error_report("uffd_copy_page() failed: dst_addr=%p src_addr=%p length=%" PRIu64
" mode=%" PRIx64 " errno=%i", dst_addr, src_addr,
length, (uint64_t) uffd_copy.mode, errno);
return -1;
length, (uint64_t) uffd_copy.mode, e);
return -e;
}
return 0;
@ -273,7 +274,7 @@ int uffd_copy_page(int uffd_fd, void *dst_addr, void *src_addr,
*
* Fill range pages with zeroes to resolve missing page fault within the range.
*
* Returns 0 on success, negative value in case of an error
* Returns 0 on success, -errno in case of an error
*
* @uffd_fd: UFFD file descriptor
* @addr: base address
@ -289,10 +290,11 @@ int uffd_zero_page(int uffd_fd, void *addr, uint64_t length, bool dont_wake)
uffd_zeropage.mode = dont_wake ? UFFDIO_ZEROPAGE_MODE_DONTWAKE : 0;
if (ioctl(uffd_fd, UFFDIO_ZEROPAGE, &uffd_zeropage)) {
int e = errno;
error_report("uffd_zero_page() failed: addr=%p length=%" PRIu64
" mode=%" PRIx64 " errno=%i", addr, length,
(uint64_t) uffd_zeropage.mode, errno);
return -1;
(uint64_t) uffd_zeropage.mode, e);
return -e;
}
return 0;
@ -306,7 +308,7 @@ int uffd_zero_page(int uffd_fd, void *addr, uint64_t length, bool dont_wake)
* via UFFD-IO IOCTLs with MODE_DONTWAKE flag set, then after that all waits
* for the whole memory range are satisfied in a single call to uffd_wakeup().
*
* Returns 0 on success, negative value in case of an error
* Returns 0 on success, -errno in case of an error
*
* @uffd_fd: UFFD file descriptor
* @addr: base address
@ -320,9 +322,10 @@ int uffd_wakeup(int uffd_fd, void *addr, uint64_t length)
uffd_range.len = length;
if (ioctl(uffd_fd, UFFDIO_WAKE, &uffd_range)) {
int e = errno;
error_report("uffd_wakeup() failed: addr=%p length=%" PRIu64 " errno=%i",
addr, length, errno);
return -1;
addr, length, e);
return -e;
}
return 0;
@ -355,31 +358,3 @@ int uffd_read_events(int uffd_fd, struct uffd_msg *msgs, int count)
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_fd: UFFD file descriptor
* @tmo: timeout value
*/
bool uffd_poll_events(int uffd_fd, int tmo)
{
int res;
struct pollfd poll_fd = { .fd = uffd_fd, .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;
}