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
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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

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# 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>

docs/about/deprecated.rst

@@ -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.

include/qemu/iova-tree.h

@@ -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:
  *

include/qemu/userfaultfd.h

@@ -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 */
 

migration/multifd-nocomp.c

@@ -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++) {

migration/multifd-qpl.c

@@ -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];
     }
 

migration/options.c

@@ -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;

migration/options.h

@@ -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 */
 

migration/postcopy-ram.c

@@ -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);
+    return uffd_wakeup(pcfd->fd,
-    range.len = pagesize;
+                       (void *)(uintptr_t)ROUND_DOWN(client_addr, pagesize),
-    ret = ioctl(pcfd->fd, UFFDIO_WAKE, &range);
+                       pagesize);
-    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;
 }
 
 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;
+        ret = uffd_copy_page(userfault_fd, host_addr, from_addr, pagesize,
-        copy_struct.dst = (uint64_t)(uintptr_t)host_addr;
+                             false);
-        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;
+        ret = uffd_zero_page(userfault_fd, host_addr, pagesize, false);
-        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) {
         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)) {
+    e = qemu_ufd_copy_ioctl(mis, host, from, pagesize, rb);
-        int e = errno;
+    if (e) {
-        error_report("%s: %s copy host: %p from: %p (size: %zd)",
+        return e;
-                     __func__, strerror(e), host, from, pagesize);
-
-        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;
-            int e = errno;
+        e = qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb);
-            error_report("%s: %s zero host: %p",
+        if (e) {
-                         __func__, strerror(e), host);
+            return e;
-
-            return -e;
         }
         return postcopy_notify_shared_wake(rb,
                                            qemu_ram_block_host_offset(rb,

migration/socket.c

@@ -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;

migration/socket.h

@@ -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);
 

qapi/migration.json

@@ -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',

system/memory.c

@@ -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);
     }

tests/qtest/migration-test.c

@@ -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, "{}");

util/iova-tree.c

@@ -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;

util/userfaultfd.c

@@ -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);
+                length, (uint64_t) uffd_copy.mode, e);
-        return -1;
+        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);
+                (uint64_t) uffd_zeropage.mode, e);
-        return -1;
+        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);
+                addr, length, e);
-        return -1;
+        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;
-}