kernel/linux.git/drivers/vhost/net.c, branch v6.18.21

virtio: clean up features qword/dword terms

2025-12-18T13:03:24+00:00

[ Upstream commit 9513f25056b22100ddffe24898c587873b0d022c ] virtio pci uses word to mean "16 bits". mmio uses it to mean "32 bits". To avoid confusion, let's avoid the term in core virtio altogether. Just say U64 to mean "64 bit". Fixes: e7d4c1c5a546 ("virtio: introduce extended features") Cc: Paolo Abeni Acked-by: Jason Wang Message-ID: Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin

vhost: rewind next_avail_head while discarding descriptors

2025-11-26T22:44:58+00:00

When discarding descriptors with IN_ORDER, we should rewind next_avail_head otherwise it would run out of sync with last_avail_idx. This would cause driver to report "id X is not a head". Fixing this by returning the number of descriptors that is used for each buffer via vhost_get_vq_desc_n() so caller can use the value while discarding descriptors. Fixes: 67a873df0c41 ("vhost: basic in order support") Cc: stable@vger.kernel.org Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Link: https://patch.msgid.link/20251120022950.10117-1-jasowang@redhat.com Signed-off-by: Jakub Kicinski

vhost-net: flush batched before enabling notifications

2025-09-19T08:15:26+00:00

Commit 8c2e6b26ffe2 ("vhost/net: Defer TX queue re-enable until after sendmsg") tries to defer the notification enabling by moving the logic out of the loop after the vhost_tx_batch() when nothing new is spotted. This caused unexpected side effects as the new logic is reused for several other error conditions. A previous patch reverted 8c2e6b26ffe2. Now, bring the performance back up by flushing batched buffers before enabling notifications. Reported-by: Jon Kohler Cc: stable@vger.kernel.org Fixes: 8c2e6b26ffe2 ("vhost/net: Defer TX queue re-enable until after sendmsg") Signed-off-by: Jason Wang Signed-off-by: Michael S. Tsirkin Message-Id: <20250917063045.2042-3-jasowang@redhat.com>

Revert "vhost/net: Defer TX queue re-enable until after sendmsg"

2025-09-19T08:15:26+00:00

This reverts commit 8c2e6b26ffe243be1e78f5a4bfb1a857d6e6f6d6. It tries to defer the notification enabling by moving the logic out of the loop after the vhost_tx_batch() when nothing new is spotted. This will bring side effects as the new logic would be reused for several other error conditions. One example is the IOTLB: when there's an IOTLB miss, get_tx_bufs() might return -EAGAIN and exit the loop and see there's still available buffers, so it will queue the tx work again until userspace feed the IOTLB entry correctly. This will slowdown the tx processing and trigger the TX watchdog in the guest as reported in https://lkml.org/lkml/2025/9/10/1596. To fix, revert the change. A follow up patch will bring the performance back in a safe way. Reported-by: Jon Kohler Cc: stable@vger.kernel.org Fixes: 8c2e6b26ffe2 ("vhost/net: Defer TX queue re-enable until after sendmsg") Signed-off-by: Jason Wang Signed-off-by: Michael S. Tsirkin Message-Id: <20250917063045.2042-2-jasowang@redhat.com>

vhost-net: unbreak busy polling

2025-09-19T08:15:26+00:00

Commit 67a873df0c41 ("vhost: basic in order support") pass the number of used elem to vhost_net_rx_peek_head_len() to make sure it can signal the used correctly before trying to do busy polling. But it forgets to clear the count, this would cause the count run out of sync with handle_rx() and break the busy polling. Fixing this by passing the pointer of the count and clearing it after the signaling the used. Acked-by: Michael S. Tsirkin Cc: stable@vger.kernel.org Fixes: 67a873df0c41 ("vhost: basic in order support") Signed-off-by: Jason Wang Message-Id: <20250917063045.2042-1-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin

vhost/net: Protect ubufs with rcu read lock in vhost_net_ubuf_put()

2025-08-26T07:38:10+00:00

When operating on struct vhost_net_ubuf_ref, the following execution sequence is theoretically possible: CPU0 is finalizing DMA operation CPU1 is doing VHOST_NET_SET_BACKEND // ubufs->refcount == 2 vhost_net_ubuf_put() vhost_net_ubuf_put_wait_and_free(oldubufs) vhost_net_ubuf_put_and_wait() vhost_net_ubuf_put() int r = atomic_sub_return(1, &ubufs->refcount); // r = 1 int r = atomic_sub_return(1, &ubufs->refcount); // r = 0 wait_event(ubufs->wait, !atomic_read(&ubufs->refcount)); // no wait occurs here because condition is already true kfree(ubufs); if (unlikely(!r)) wake_up(&ubufs->wait); // use-after-free This leads to use-after-free on ubufs access. This happens because CPU1 skips waiting for wake_up() when refcount is already zero. To prevent that use a read-side RCU critical section in vhost_net_ubuf_put(), as suggested by Hillf Danton. For this lock to take effect, free ubufs with kfree_rcu(). Cc: stable@vger.kernel.org Fixes: 0ad8b480d6ee9 ("vhost: fix ref cnt checking deadlock") Reported-by: Andrey Ryabinin Suggested-by: Hillf Danton Signed-off-by: Nikolay Kuratov Message-Id: <20250805130917.727332-1-kniv@yandex-team.ru> Signed-off-by: Michael S. Tsirkin

Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

2025-08-01T21:17:48+00:00

Pull virtio updates from Michael Tsirkin: - vhost can now support legacy threading if enabled in Kconfig - vsock memory allocation strategies for large buffers have been improved, reducing pressure on kmalloc - vhost now supports the in-order feature. guest bits missed the merge window. - fixes, cleanups all over the place * tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost: (30 commits) vsock/virtio: Allocate nonlinear SKBs for handling large transmit buffers vsock/virtio: Rename virtio_vsock_skb_rx_put() vhost/vsock: Allocate nonlinear SKBs for handling large receive buffers vsock/virtio: Move SKB allocation lower-bound check to callers vsock/virtio: Rename virtio_vsock_alloc_skb() vsock/virtio: Resize receive buffers so that each SKB fits in a 4K page vsock/virtio: Move length check to callers of virtio_vsock_skb_rx_put() vsock/virtio: Validate length in packet header before skb_put() vhost/vsock: Avoid allocating arbitrarily-sized SKBs vhost_net: basic in_order support vhost: basic in order support vhost: fail early when __vhost_add_used() fails vhost: Reintroduce kthread API and add mode selection vdpa: Fix IDR memory leak in VDUSE module exit vdpa/mlx5: Fix release of uninitialized resources on error path vhost-scsi: Fix check for inline_sg_cnt exceeding preallocated limit virtio: virtio_dma_buf: fix missing parameter documentation vhost: Fix typos vhost: vringh: Remove unused functions vhost: vringh: Remove unused iotlb functions ...

vhost_net: basic in_order support

2025-08-01T13:11:09+00:00

This patch introduces basic in-order support for vhost-net. By recording the number of batched buffers in an array when calling `vhost_add_used_and_signal_n()`, we can reduce the number of userspace accesses. Note that the vhost-net batching logic is kept as we still count the number of buffers there. Testing Results: With testpmd: - TX: txonly mode + vhost_net with XDP_DROP on TAP shows a 17.5% improvement, from 4.75 Mpps to 5.35 Mpps. - RX: No obvious improvements were observed. With virtio-ring in-order experimental code in the guest: - TX: pktgen in the guest + XDP_DROP on TAP shows a 19% improvement, from 5.2 Mpps to 6.2 Mpps. - RX: pktgen on TAP with vhost_net + XDP_DROP in the guest achieves a 6.1% improvement, from 3.47 Mpps to 3.61 Mpps. Acked-by: Jonah Palmer Acked-by: Eugenio Pérez Signed-off-by: Jason Wang Message-Id: <20250714084755.11921-4-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin Tested-by: Lei Yang

vhost: basic in order support

2025-08-01T13:11:09+00:00

This patch adds basic in order support for vhost. Two optimizations are implemented in this patch: 1) Since driver uses descriptor in order, vhost can deduce the next avail ring head by counting the number of descriptors that has been used in next_avail_head. This eliminate the need to access the available ring in vhost. 2) vhost_add_used_and_singal_n() is extended to accept the number of batched buffers per used elem. While this increases the times of userspace memory access but it helps to reduce the chance of used ring access of both the driver and vhost. Vhost-net will be the first user for this. Acked-by: Jonah Palmer Signed-off-by: Jason Wang Message-Id: <20250714084755.11921-3-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin Tested-by: Lei Yang

Merge branch 'virtio_udp_tunnel_08_07_2025' of https://github.com/pabeni/linux-devel

2025-07-10T20:32:35+00:00

Paolo Abeni says: ==================== virtio: introduce GSO over UDP tunnel Some virtualized deployments use UDP tunnel pervasively and are impacted negatively by the lack of GSO support for such kind of traffic in the virtual NIC driver. The virtio_net specification recently introduced support for GSO over UDP tunnel, this series updates the virtio implementation to support such a feature. Currently the kernel virtio support limits the feature space to 64, while the virtio specification allows for a larger number of features. Specifically the GSO-over-UDP-tunnel-related virtio features use bits 65-69. The first four patches in this series rework the virtio and vhost feature support to cope with up to 128 bits. The limit is set by a define and could be easily raised in future, as needed. This implementation choice is aimed at keeping the code churn as limited as possible. For the same reason, only the virtio_net driver is reworked to leverage the extended feature space; all other virtio/vhost drivers are unaffected, but could be upgraded to support the extended features space in a later time. The last four patches bring in the actual GSO over UDP tunnel support. As per specification, some additional fields are introduced into the virtio net header to support the new offload. The presence of such fields depends on the negotiated features. New helpers are introduced to convert the UDP-tunneled skb metadata to an extended virtio net header and vice versa. Such helpers are used by the tun and virtio_net driver to cope with the newly supported offloads. Tested with basic stream transfer with all the possible permutations of host kernel/qemu/guest kernel with/without GSO over UDP tunnel support. ==================== Link: https://patch.msgid.link/cover.1751874094.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski