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Szmigiero" , kvm@vger.kernel.org, Tiwei Bie Subject: [PATCH v2 01/16] vhost: Rework memslot filtering and fix "used_memslot" tracking Date: Fri, 25 Aug 2023 15:21:34 +0200 Message-ID: <20230825132149.366064-2-david@redhat.com> In-Reply-To: <20230825132149.366064-1-david@redhat.com> References: <20230825132149.366064-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1692969811794100013 Content-Type: text/plain; charset="utf-8" Having multiple vhost devices, some filtering out fd-less memslots and some not, can mess up the "used_memslot" accounting. Consequently our "free memslot" checks become unreliable and we might run out of free memslots at runtime later. An example sequence which can trigger a potential issue that involves different vhost backends (vhost-kernel and vhost-user) and hotplugged memory devices can be found at [1]. Let's make the filtering mechanism less generic and distinguish between backends that support private memslots (without a fd) and ones that only support shared memslots (with a fd). Track the used_memslots for both cases separately and use the corresponding value when required. Note: Most probably we should filter out MAP_PRIVATE fd-based RAM regions (for example, via memory-backend-memfd,...,shared=3Doff or as default with memory-backend-file) as well. When not using MAP_SHARED, it might not work as expected. Add a TODO for now. [1] https://lkml.kernel.org/r/fad9136f-08d3-3fd9-71a1-502069c000cf@redhat.c= om Fixes: 988a27754bbb ("vhost: allow backends to filter memory sections") Cc: Tiwei Bie Acked-by: Igor Mammedov Reviewed-by: Peter Xu Signed-off-by: David Hildenbrand --- hw/virtio/vhost-user.c | 7 ++-- hw/virtio/vhost.c | 56 ++++++++++++++++++++++++++----- include/hw/virtio/vhost-backend.h | 5 ++- 3 files changed, 52 insertions(+), 16 deletions(-) diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index 8dcf049d42..1e7553352a 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -2500,10 +2500,9 @@ vhost_user_crypto_close_session(struct vhost_dev *de= v, uint64_t session_id) return 0; } =20 -static bool vhost_user_mem_section_filter(struct vhost_dev *dev, - MemoryRegionSection *section) +static bool vhost_user_no_private_memslots(struct vhost_dev *dev) { - return memory_region_get_fd(section->mr) >=3D 0; + return true; } =20 static int vhost_user_get_inflight_fd(struct vhost_dev *dev, @@ -2746,6 +2745,7 @@ const VhostOps user_ops =3D { .vhost_backend_init =3D vhost_user_backend_init, .vhost_backend_cleanup =3D vhost_user_backend_cleanup, .vhost_backend_memslots_limit =3D vhost_user_memslots_limit, + .vhost_backend_no_private_memslots =3D vhost_user_no_private_memsl= ots, .vhost_set_log_base =3D vhost_user_set_log_base, .vhost_set_mem_table =3D vhost_user_set_mem_table, .vhost_set_vring_addr =3D vhost_user_set_vring_addr, @@ -2772,7 +2772,6 @@ const VhostOps user_ops =3D { .vhost_set_config =3D vhost_user_set_config, .vhost_crypto_create_session =3D vhost_user_crypto_create_session, .vhost_crypto_close_session =3D vhost_user_crypto_close_session, - .vhost_backend_mem_section_filter =3D vhost_user_mem_section_filte= r, .vhost_get_inflight_fd =3D vhost_user_get_inflight_fd, .vhost_set_inflight_fd =3D vhost_user_set_inflight_fd, .vhost_dev_start =3D vhost_user_dev_start, diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index e2f6ffb446..c1e6148833 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -45,20 +45,33 @@ static struct vhost_log *vhost_log; static struct vhost_log *vhost_log_shm; =20 +/* Memslots used by backends that support private memslots (without an fd)= . */ static unsigned int used_memslots; + +/* Memslots used by backends that only support shared memslots (with an fd= ). */ +static unsigned int used_shared_memslots; + static QLIST_HEAD(, vhost_dev) vhost_devices =3D QLIST_HEAD_INITIALIZER(vhost_devices); =20 bool vhost_has_free_slot(void) { - unsigned int slots_limit =3D ~0U; + unsigned int free =3D UINT_MAX; struct vhost_dev *hdev; =20 QLIST_FOREACH(hdev, &vhost_devices, entry) { unsigned int r =3D hdev->vhost_ops->vhost_backend_memslots_limit(h= dev); - slots_limit =3D MIN(slots_limit, r); + unsigned int cur_free; + + if (hdev->vhost_ops->vhost_backend_no_private_memslots && + hdev->vhost_ops->vhost_backend_no_private_memslots(hdev)) { + cur_free =3D r - used_shared_memslots; + } else { + cur_free =3D r - used_memslots; + } + free =3D MIN(free, cur_free); } - return slots_limit > used_memslots; + return free > 0; } =20 static void vhost_dev_sync_region(struct vhost_dev *dev, @@ -474,8 +487,7 @@ static int vhost_verify_ring_mappings(struct vhost_dev = *dev, * vhost_section: identify sections needed for vhost access * * We only care about RAM sections here (where virtqueue and guest - * internals accessed by virtio might live). If we find one we still - * allow the backend to potentially filter it out of our list. + * internals accessed by virtio might live). */ static bool vhost_section(struct vhost_dev *dev, MemoryRegionSection *sect= ion) { @@ -502,8 +514,16 @@ static bool vhost_section(struct vhost_dev *dev, Memor= yRegionSection *section) return false; } =20 - if (dev->vhost_ops->vhost_backend_mem_section_filter && - !dev->vhost_ops->vhost_backend_mem_section_filter(dev, section= )) { + /* + * Some backends (like vhost-user) can only handle memory regions + * that have an fd (can be mapped into a different process). Filter + * the ones without an fd out, if requested. + * + * TODO: we might have to limit to MAP_SHARED as well. + */ + if (memory_region_get_fd(section->mr) < 0 && + dev->vhost_ops->vhost_backend_no_private_memslots && + dev->vhost_ops->vhost_backend_no_private_memslots(dev)) { trace_vhost_reject_section(mr->name, 2); return false; } @@ -568,7 +588,14 @@ static void vhost_commit(MemoryListener *listener) dev->n_mem_sections * sizeof dev->mem->regions[0]; dev->mem =3D g_realloc(dev->mem, regions_size); dev->mem->nregions =3D dev->n_mem_sections; - used_memslots =3D dev->mem->nregions; + + if (dev->vhost_ops->vhost_backend_no_private_memslots && + dev->vhost_ops->vhost_backend_no_private_memslots(dev)) { + used_shared_memslots =3D dev->mem->nregions; + } else { + used_memslots =3D dev->mem->nregions; + } + for (i =3D 0; i < dev->n_mem_sections; i++) { struct vhost_memory_region *cur_vmr =3D dev->mem->regions + i; struct MemoryRegionSection *mrs =3D dev->mem_sections + i; @@ -1400,6 +1427,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaq= ue, VhostBackendType backend_type, uint32_t busyloop_timeou= t, Error **errp) { + unsigned int used; uint64_t features; int i, r, n_initialized_vqs =3D 0; =20 @@ -1495,7 +1523,17 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opa= que, memory_listener_register(&hdev->memory_listener, &address_space_memory= ); QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); =20 - if (used_memslots > hdev->vhost_ops->vhost_backend_memslots_limit(hdev= )) { + /* + * The listener we registered properly updated the corresponding count= er. + * So we can trust that these values are accurate. + */ + if (hdev->vhost_ops->vhost_backend_no_private_memslots && + hdev->vhost_ops->vhost_backend_no_private_memslots(hdev)) { + used =3D used_shared_memslots; + } else { + used =3D used_memslots; + } + if (used > hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { error_setg(errp, "vhost backend memory slots limit is less" " than current number of present memory slots"); r =3D -EINVAL; diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-ba= ckend.h index 31a251a9f5..df2821ddae 100644 --- a/include/hw/virtio/vhost-backend.h +++ b/include/hw/virtio/vhost-backend.h @@ -108,8 +108,7 @@ typedef int (*vhost_crypto_create_session_op)(struct vh= ost_dev *dev, typedef int (*vhost_crypto_close_session_op)(struct vhost_dev *dev, uint64_t session_id); =20 -typedef bool (*vhost_backend_mem_section_filter_op)(struct vhost_dev *dev, - MemoryRegionSection *secti= on); +typedef bool (*vhost_backend_no_private_memslots_op)(struct vhost_dev *dev= ); =20 typedef int (*vhost_get_inflight_fd_op)(struct vhost_dev *dev, uint16_t queue_size, @@ -138,6 +137,7 @@ typedef struct VhostOps { vhost_backend_init vhost_backend_init; vhost_backend_cleanup vhost_backend_cleanup; vhost_backend_memslots_limit vhost_backend_memslots_limit; + vhost_backend_no_private_memslots_op vhost_backend_no_private_memslots; vhost_net_set_backend_op vhost_net_set_backend; vhost_net_set_mtu_op vhost_net_set_mtu; vhost_scsi_set_endpoint_op vhost_scsi_set_endpoint; @@ -172,7 +172,6 @@ typedef struct VhostOps { vhost_set_config_op vhost_set_config; vhost_crypto_create_session_op vhost_crypto_create_session; vhost_crypto_close_session_op vhost_crypto_close_session; - vhost_backend_mem_section_filter_op vhost_backend_mem_section_filter; vhost_get_inflight_fd_op vhost_get_inflight_fd; vhost_set_inflight_fd_op vhost_set_inflight_fd; vhost_dev_start_op vhost_dev_start; --=20 2.41.0