| Message ID | 20241010061824.74819-1-yaozhenguo@jd.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [V3] virtio/vhost-user: fix qemu abort when hotunplug vhost-user-net device | expand |
On Thu, Oct 10, 2024 at 02:18:24PM GMT, yaozhenguo wrote: >During the hot-unplugging of vhost-user-net type network cards, >the vhost_user_cleanup function may add the same rcu node to >the rcu linked list. >The function call relationship in this case is as follows: > >vhost_user_cleanup > ->vhost_user_host_notifier_remove > ->call_rcu(n, vhost_user_host_notifier_free, rcu); > ->g_free_rcu(n, rcu); > >When this happens, QEMU will abort in try_dequeue: > >if (head == &dummy && qatomic_mb_read(&tail) == &dummy.next) { > abort(); >} > >backtrace is as follows:: >0 __pthread_kill_implementation () at /usr/lib64/libc.so.6 >1 raise () at /usr/lib64/libc.so.6 >2 abort () at /usr/lib64/libc.so.6 >3 try_dequeue () at ../util/rcu.c:235 >4 call_rcu_thread (0) at ../util/rcu.c:288 >5 qemu_thread_start (0) at ../util/qemu-thread-posix.c:541 >6 start_thread () at /usr/lib64/libc.so.6 >7 clone3 () at /usr/lib64/libc.so.6 > >The reason for the abort is that adding two identical nodes to >the rcu linked list will cause the rcu linked list to become a ring, >but when the dummy node is added after the two identical nodes, >the ring is opened. But only one node is added to list with >rcu_call_count added twice. This will cause rcu try_dequeue abort. > >This happens when n->addr != 0. In some scenarios, this does happen. >For example, this situation will occur when using a 32-queue DPU >vhost-user-net type network card for hot-unplug testing, because >VhostUserHostNotifier->addr will be cleared during the processing of >VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG. However,it is asynchronous, >so we cannot guarantee that VhostUserHostNotifier->addr is zero in >vhost_user_cleanup. Therefore, it is necessary to merge g_free_rcu >and vhost_user_host_notifier_free into one rcu node. > >Fixes: 503e355465 ("virtio/vhost-user: dynamically assign VhostUserHostNotifiers") >Signed-off-by: yaozhenguo <yaozhenguo@jd.com> >--- > V1->V2: add n->addr check in vhost_user_get_vring_base and vhost_user_backend_handle_vring_host_notifier to prevent submit same node to rcu list. > V2->V3: 1. change "free" to "destroy" > 2. move "!n->addr && !destroy" checking to vhost_user_host_notifier_remove > 3. move "!n" checking to vhost_user_host_notifier_remove >--- > hw/virtio/vhost-user.c | 43 ++++++++++++++++++---------------- > include/hw/virtio/vhost-user.h | 1 + > 2 files changed, 24 insertions(+), 20 deletions(-) Some checkpatch errors: $ ./scripts/checkpatch.pl --strict --branch master..HEAD --codespell ERROR: braces {} are necessary for all arms of this statement #98: FILE: hw/virtio/vhost-user.c:1207: + if (!n) [...] ERROR: braces {} are necessary for all arms of this statement #100: FILE: hw/virtio/vhost-user.c:1209: + if (!destroy && !n->addr) [...] total: 2 errors, 0 warnings, 96 lines checked > >diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c >index 00561daa06..f80d0af76f 100644 >--- a/hw/virtio/vhost-user.c >+++ b/hw/virtio/vhost-user.c >@@ -1185,9 +1185,16 @@ static int vhost_user_set_vring_num(struct vhost_dev *dev, > > static void vhost_user_host_notifier_free(VhostUserHostNotifier *n) > { >- assert(n && n->unmap_addr); >- munmap(n->unmap_addr, qemu_real_host_page_size()); >- n->unmap_addr = NULL; >+ if (n->unmap_addr) { >+ munmap(n->unmap_addr, qemu_real_host_page_size()); >+ n->unmap_addr = NULL; >+ } >+ if (n->destroy) { >+ memory_region_transaction_begin(); >+ object_unparent(OBJECT(&n->mr)); >+ memory_region_transaction_commit(); >+ g_free(n); >+ } > } > > /* >@@ -1195,17 +1202,25 @@ static void vhost_user_host_notifier_free(VhostUserHostNotifier *n) > * under rcu. > */ > static void vhost_user_host_notifier_remove(VhostUserHostNotifier *n, >- VirtIODevice *vdev) >+ VirtIODevice *vdev, bool destroy) > { >+ if (!n) >+ return; >+ if (!destroy && !n->addr) IIUC if `destroy` is false and `n->addr` is NULL, we don't have anything to do, so we can early return, right? Maybe we can put a comment on that condition. >+ return; Better to use a single if here in this way: if (!n || (!destroy && !n->addr)) { return; } The rest LGTM! Thanks, Stefano >+ > if (n->addr) { > if (vdev) { >+ memory_region_transaction_begin(); > virtio_queue_set_host_notifier_mr(vdev, n->idx, &n->mr, false); >+ memory_region_transaction_commit(); > } > assert(!n->unmap_addr); > n->unmap_addr = n->addr; > n->addr = NULL; >- call_rcu(n, vhost_user_host_notifier_free, rcu); > } >+ n->destroy = destroy; >+ call_rcu(n, vhost_user_host_notifier_free, rcu); > } > > static int vhost_user_set_vring_base(struct vhost_dev *dev, >@@ -1279,9 +1294,7 @@ static int vhost_user_get_vring_base(struct vhost_dev *dev, > struct vhost_user *u = dev->opaque; > > VhostUserHostNotifier *n = fetch_notifier(u->user, ring->index); >- if (n) { >- vhost_user_host_notifier_remove(n, dev->vdev); >- } >+ vhost_user_host_notifier_remove(n, dev->vdev, false); > > ret = vhost_user_write(dev, &msg, NULL, 0); > if (ret < 0) { >@@ -1562,7 +1575,7 @@ static int vhost_user_backend_handle_vring_host_notifier(struct vhost_dev *dev, > * new mapped address. > */ > n = fetch_or_create_notifier(user, queue_idx); >- vhost_user_host_notifier_remove(n, vdev); >+ vhost_user_host_notifier_remove(n, vdev, false); > > if (area->u64 & VHOST_USER_VRING_NOFD_MASK) { > return 0; >@@ -2736,15 +2749,7 @@ static int vhost_user_set_inflight_fd(struct vhost_dev *dev, > static void vhost_user_state_destroy(gpointer data) > { > VhostUserHostNotifier *n = (VhostUserHostNotifier *) data; >- if (n) { >- vhost_user_host_notifier_remove(n, NULL); >- object_unparent(OBJECT(&n->mr)); >- /* >- * We can't free until vhost_user_host_notifier_remove has >- * done it's thing so schedule the free with RCU. >- */ >- g_free_rcu(n, rcu); >- } >+ vhost_user_host_notifier_remove(n, NULL, true); > } > > bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp) >@@ -2765,9 +2770,7 @@ void vhost_user_cleanup(VhostUserState *user) > if (!user->chr) { > return; > } >- memory_region_transaction_begin(); > user->notifiers = (GPtrArray *) g_ptr_array_free(user->notifiers, true); >- memory_region_transaction_commit(); > user->chr = NULL; > } > >diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h >index 324cd8663a..9a3f238b43 100644 >--- a/include/hw/virtio/vhost-user.h >+++ b/include/hw/virtio/vhost-user.h >@@ -54,6 +54,7 @@ typedef struct VhostUserHostNotifier { > void *addr; > void *unmap_addr; > int idx; >+ bool destroy; > } VhostUserHostNotifier; > > /** >-- >2.41.0 >
Stefano Garzarella <sgarzare@redhat.com> 于2024年10月10日周四 16:20写道： > > On Thu, Oct 10, 2024 at 02:18:24PM GMT, yaozhenguo wrote: > >During the hot-unplugging of vhost-user-net type network cards, > >the vhost_user_cleanup function may add the same rcu node to > >the rcu linked list. > >The function call relationship in this case is as follows: > > > >vhost_user_cleanup > > ->vhost_user_host_notifier_remove > > ->call_rcu(n, vhost_user_host_notifier_free, rcu); > > ->g_free_rcu(n, rcu); > > > >When this happens, QEMU will abort in try_dequeue: > > > >if (head == &dummy && qatomic_mb_read(&tail) == &dummy.next) { > > abort(); > >} > > > >backtrace is as follows:: > >0 __pthread_kill_implementation () at /usr/lib64/libc.so.6 > >1 raise () at /usr/lib64/libc.so.6 > >2 abort () at /usr/lib64/libc.so.6 > >3 try_dequeue () at ../util/rcu.c:235 > >4 call_rcu_thread (0) at ../util/rcu.c:288 > >5 qemu_thread_start (0) at ../util/qemu-thread-posix.c:541 > >6 start_thread () at /usr/lib64/libc.so.6 > >7 clone3 () at /usr/lib64/libc.so.6 > > > >The reason for the abort is that adding two identical nodes to > >the rcu linked list will cause the rcu linked list to become a ring, > >but when the dummy node is added after the two identical nodes, > >the ring is opened. But only one node is added to list with > >rcu_call_count added twice. This will cause rcu try_dequeue abort. > > > >This happens when n->addr != 0. In some scenarios, this does happen. > >For example, this situation will occur when using a 32-queue DPU > >vhost-user-net type network card for hot-unplug testing, because > >VhostUserHostNotifier->addr will be cleared during the processing of > >VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG. However,it is asynchronous, > >so we cannot guarantee that VhostUserHostNotifier->addr is zero in > >vhost_user_cleanup. Therefore, it is necessary to merge g_free_rcu > >and vhost_user_host_notifier_free into one rcu node. > > > >Fixes: 503e355465 ("virtio/vhost-user: dynamically assign VhostUserHostNotifiers") > >Signed-off-by: yaozhenguo <yaozhenguo@jd.com> > >--- > > V1->V2: add n->addr check in vhost_user_get_vring_base and vhost_user_backend_handle_vring_host_notifier to prevent submit same node to rcu list. > > V2->V3: 1. change "free" to "destroy" > > 2. move "!n->addr && !destroy" checking to vhost_user_host_notifier_remove > > 3. move "!n" checking to vhost_user_host_notifier_remove > >--- > > hw/virtio/vhost-user.c | 43 ++++++++++++++++++---------------- > > include/hw/virtio/vhost-user.h | 1 + > > 2 files changed, 24 insertions(+), 20 deletions(-) > > Some checkpatch errors: > > $ ./scripts/checkpatch.pl --strict --branch master..HEAD --codespell > ERROR: braces {} are necessary for all arms of this statement > #98: FILE: hw/virtio/vhost-user.c:1207: > + if (!n) > [...] > > ERROR: braces {} are necessary for all arms of this statement > #100: FILE: hw/virtio/vhost-user.c:1209: > + if (!destroy && !n->addr) > [...] > > total: 2 errors, 0 warnings, 96 lines checked > I will fix it later. > > > >diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > >index 00561daa06..f80d0af76f 100644 > >--- a/hw/virtio/vhost-user.c > >+++ b/hw/virtio/vhost-user.c > >@@ -1185,9 +1185,16 @@ static int vhost_user_set_vring_num(struct vhost_dev *dev, > > > > static void vhost_user_host_notifier_free(VhostUserHostNotifier *n) > > { > >- assert(n && n->unmap_addr); > >- munmap(n->unmap_addr, qemu_real_host_page_size()); > >- n->unmap_addr = NULL; > >+ if (n->unmap_addr) { > >+ munmap(n->unmap_addr, qemu_real_host_page_size()); > >+ n->unmap_addr = NULL; > >+ } > >+ if (n->destroy) { > >+ memory_region_transaction_begin(); > >+ object_unparent(OBJECT(&n->mr)); > >+ memory_region_transaction_commit(); > >+ g_free(n); > >+ } > > } > > > > /* > >@@ -1195,17 +1202,25 @@ static void vhost_user_host_notifier_free(VhostUserHostNotifier *n) > > * under rcu. > > */ > > static void vhost_user_host_notifier_remove(VhostUserHostNotifier *n, > >- VirtIODevice *vdev) > >+ VirtIODevice *vdev, bool destroy) > > { > >+ if (!n) > >+ return; > >+ if (!destroy && !n->addr) > > IIUC if `destroy` is false and `n->addr` is NULL, we don't have anything > to do, so we can early return, right? > Yes. > Maybe we can put a comment on that condition. > > >+ return; > > Better to use a single if here in this way: > if (!n || (!destroy && !n->addr)) { > return; > } > Got it! > The rest LGTM! > > Thanks, > Stefano > > >+ > > if (n->addr) { > > if (vdev) { > >+ memory_region_transaction_begin(); > > virtio_queue_set_host_notifier_mr(vdev, n->idx, &n->mr, false); > >+ memory_region_transaction_commit(); > > } > > assert(!n->unmap_addr); > > n->unmap_addr = n->addr; > > n->addr = NULL; > >- call_rcu(n, vhost_user_host_notifier_free, rcu); > > } > >+ n->destroy = destroy; > >+ call_rcu(n, vhost_user_host_notifier_free, rcu); > > } > > > > static int vhost_user_set_vring_base(struct vhost_dev *dev, > >@@ -1279,9 +1294,7 @@ static int vhost_user_get_vring_base(struct vhost_dev *dev, > > struct vhost_user *u = dev->opaque; > > > > VhostUserHostNotifier *n = fetch_notifier(u->user, ring->index); > >- if (n) { > >- vhost_user_host_notifier_remove(n, dev->vdev); > >- } > >+ vhost_user_host_notifier_remove(n, dev->vdev, false); > > > > ret = vhost_user_write(dev, &msg, NULL, 0); > > if (ret < 0) { > >@@ -1562,7 +1575,7 @@ static int vhost_user_backend_handle_vring_host_notifier(struct vhost_dev *dev, > > * new mapped address. > > */ > > n = fetch_or_create_notifier(user, queue_idx); > >- vhost_user_host_notifier_remove(n, vdev); > >+ vhost_user_host_notifier_remove(n, vdev, false); > > > > if (area->u64 & VHOST_USER_VRING_NOFD_MASK) { > > return 0; > >@@ -2736,15 +2749,7 @@ static int vhost_user_set_inflight_fd(struct vhost_dev *dev, > > static void vhost_user_state_destroy(gpointer data) > > { > > VhostUserHostNotifier *n = (VhostUserHostNotifier *) data; > >- if (n) { > >- vhost_user_host_notifier_remove(n, NULL); > >- object_unparent(OBJECT(&n->mr)); > >- /* > >- * We can't free until vhost_user_host_notifier_remove has > >- * done it's thing so schedule the free with RCU. > >- */ > >- g_free_rcu(n, rcu); > >- } > >+ vhost_user_host_notifier_remove(n, NULL, true); > > } > > > > bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp) > >@@ -2765,9 +2770,7 @@ void vhost_user_cleanup(VhostUserState *user) > > if (!user->chr) { > > return; > > } > >- memory_region_transaction_begin(); > > user->notifiers = (GPtrArray *) g_ptr_array_free(user->notifiers, true); > >- memory_region_transaction_commit(); > > user->chr = NULL; > > } > > > >diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h > >index 324cd8663a..9a3f238b43 100644 > >--- a/include/hw/virtio/vhost-user.h > >+++ b/include/hw/virtio/vhost-user.h > >@@ -54,6 +54,7 @@ typedef struct VhostUserHostNotifier { > > void *addr; > > void *unmap_addr; > > int idx; > >+ bool destroy; > > } VhostUserHostNotifier; > > > > /** > >-- > >2.41.0 > > >
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index 00561daa06..f80d0af76f 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -1185,9 +1185,16 @@ static int vhost_user_set_vring_num(struct vhost_dev *dev, static void vhost_user_host_notifier_free(VhostUserHostNotifier *n) { - assert(n && n->unmap_addr); - munmap(n->unmap_addr, qemu_real_host_page_size()); - n->unmap_addr = NULL; + if (n->unmap_addr) { + munmap(n->unmap_addr, qemu_real_host_page_size()); + n->unmap_addr = NULL; + } + if (n->destroy) { + memory_region_transaction_begin(); + object_unparent(OBJECT(&n->mr)); + memory_region_transaction_commit(); + g_free(n); + } } /* @@ -1195,17 +1202,25 @@ static void vhost_user_host_notifier_free(VhostUserHostNotifier *n) * under rcu. */ static void vhost_user_host_notifier_remove(VhostUserHostNotifier *n, - VirtIODevice *vdev) + VirtIODevice *vdev, bool destroy) { + if (!n) + return; + if (!destroy && !n->addr) + return; + if (n->addr) { if (vdev) { + memory_region_transaction_begin(); virtio_queue_set_host_notifier_mr(vdev, n->idx, &n->mr, false); + memory_region_transaction_commit(); } assert(!n->unmap_addr); n->unmap_addr = n->addr; n->addr = NULL; - call_rcu(n, vhost_user_host_notifier_free, rcu); } + n->destroy = destroy; + call_rcu(n, vhost_user_host_notifier_free, rcu); } static int vhost_user_set_vring_base(struct vhost_dev *dev, @@ -1279,9 +1294,7 @@ static int vhost_user_get_vring_base(struct vhost_dev *dev, struct vhost_user *u = dev->opaque; VhostUserHostNotifier *n = fetch_notifier(u->user, ring->index); - if (n) { - vhost_user_host_notifier_remove(n, dev->vdev); - } + vhost_user_host_notifier_remove(n, dev->vdev, false); ret = vhost_user_write(dev, &msg, NULL, 0); if (ret < 0) { @@ -1562,7 +1575,7 @@ static int vhost_user_backend_handle_vring_host_notifier(struct vhost_dev *dev, * new mapped address. */ n = fetch_or_create_notifier(user, queue_idx); - vhost_user_host_notifier_remove(n, vdev); + vhost_user_host_notifier_remove(n, vdev, false); if (area->u64 & VHOST_USER_VRING_NOFD_MASK) { return 0; @@ -2736,15 +2749,7 @@ static int vhost_user_set_inflight_fd(struct vhost_dev *dev, static void vhost_user_state_destroy(gpointer data) { VhostUserHostNotifier *n = (VhostUserHostNotifier *) data; - if (n) { - vhost_user_host_notifier_remove(n, NULL); - object_unparent(OBJECT(&n->mr)); - /* - * We can't free until vhost_user_host_notifier_remove has - * done it's thing so schedule the free with RCU. - */ - g_free_rcu(n, rcu); - } + vhost_user_host_notifier_remove(n, NULL, true); } bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp) @@ -2765,9 +2770,7 @@ void vhost_user_cleanup(VhostUserState *user) if (!user->chr) { return; } - memory_region_transaction_begin(); user->notifiers = (GPtrArray *) g_ptr_array_free(user->notifiers, true); - memory_region_transaction_commit(); user->chr = NULL; } diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h index 324cd8663a..9a3f238b43 100644 --- a/include/hw/virtio/vhost-user.h +++ b/include/hw/virtio/vhost-user.h @@ -54,6 +54,7 @@ typedef struct VhostUserHostNotifier { void *addr; void *unmap_addr; int idx; + bool destroy; } VhostUserHostNotifier; /**
During the hot-unplugging of vhost-user-net type network cards, the vhost_user_cleanup function may add the same rcu node to the rcu linked list. The function call relationship in this case is as follows: vhost_user_cleanup ->vhost_user_host_notifier_remove ->call_rcu(n, vhost_user_host_notifier_free, rcu); ->g_free_rcu(n, rcu); When this happens, QEMU will abort in try_dequeue: if (head == &dummy && qatomic_mb_read(&tail) == &dummy.next) { abort(); } backtrace is as follows:: 0 __pthread_kill_implementation () at /usr/lib64/libc.so.6 1 raise () at /usr/lib64/libc.so.6 2 abort () at /usr/lib64/libc.so.6 3 try_dequeue () at ../util/rcu.c:235 4 call_rcu_thread (0) at ../util/rcu.c:288 5 qemu_thread_start (0) at ../util/qemu-thread-posix.c:541 6 start_thread () at /usr/lib64/libc.so.6 7 clone3 () at /usr/lib64/libc.so.6 The reason for the abort is that adding two identical nodes to the rcu linked list will cause the rcu linked list to become a ring, but when the dummy node is added after the two identical nodes, the ring is opened. But only one node is added to list with rcu_call_count added twice. This will cause rcu try_dequeue abort. This happens when n->addr != 0. In some scenarios, this does happen. For example, this situation will occur when using a 32-queue DPU vhost-user-net type network card for hot-unplug testing, because VhostUserHostNotifier->addr will be cleared during the processing of VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG. However,it is asynchronous, so we cannot guarantee that VhostUserHostNotifier->addr is zero in vhost_user_cleanup. Therefore, it is necessary to merge g_free_rcu and vhost_user_host_notifier_free into one rcu node. Fixes: 503e355465 ("virtio/vhost-user: dynamically assign VhostUserHostNotifiers") Signed-off-by: yaozhenguo <yaozhenguo@jd.com> --- V1->V2: add n->addr check in vhost_user_get_vring_base and vhost_user_backend_handle_vring_host_notifier to prevent submit same node to rcu list. V2->V3: 1. change "free" to "destroy" 2. move "!n->addr && !destroy" checking to vhost_user_host_notifier_remove 3. move "!n" checking to vhost_user_host_notifier_remove --- hw/virtio/vhost-user.c | 43 ++++++++++++++++++---------------- include/hw/virtio/vhost-user.h | 1 + 2 files changed, 24 insertions(+), 20 deletions(-)