From 621be0aeda544fcf81e80f8ed96faad504aa119e Mon Sep 17 00:00:00 2001 From: vmaffione Date: Sun, 3 Nov 2019 19:02:32 +0000 Subject: [PATCH] bhyve: add backend rx backpressure to virtio-net If a VM is flooded with more ingress packets than the guest OS can handle, the current virtio-net code will keep reading those packets and drop most of them as no space is available in the receive queue. This is an undesirable receive livelock, which is a waste of CPU and memory resources and potentially opens to DoS attacks. With this change, virtio-net uses the new netbe_rx_disable() function to disable ingress operation in the backend while the guest is short on RX buffers. Once the guest makes more buffers available to the RX virtqueue, ingress operation is enabled again by calling netbe_rx_enable(). Reviewed by: bryanv, jhb MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D20987 --- usr.sbin/bhyve/mevent.c | 8 +++++ usr.sbin/bhyve/mevent.h | 3 ++ usr.sbin/bhyve/net_backends.c | 4 +-- usr.sbin/bhyve/pci_e82545.c | 2 ++ usr.sbin/bhyve/pci_virtio_net.c | 56 +++++++++++++++------------------ 5 files changed, 40 insertions(+), 33 deletions(-) diff --git a/usr.sbin/bhyve/mevent.c b/usr.sbin/bhyve/mevent.c index 60289df6c9a..ceb4c4f52ec 100644 --- a/usr.sbin/bhyve/mevent.c +++ b/usr.sbin/bhyve/mevent.c @@ -321,6 +321,14 @@ mevent_add(int tfd, enum ev_type type, return mevent_add_state(tfd, type, func, param, MEV_ADD); } +struct mevent * +mevent_add_disabled(int tfd, enum ev_type type, + void (*func)(int, enum ev_type, void *), void *param) +{ + + return mevent_add_state(tfd, type, func, param, MEV_ADD_DISABLED); +} + static int mevent_update(struct mevent *evp, int newstate) { diff --git a/usr.sbin/bhyve/mevent.h b/usr.sbin/bhyve/mevent.h index e6b96f0a7c8..503ec415a3b 100644 --- a/usr.sbin/bhyve/mevent.h +++ b/usr.sbin/bhyve/mevent.h @@ -43,6 +43,9 @@ struct mevent; struct mevent *mevent_add(int fd, enum ev_type type, void (*func)(int, enum ev_type, void *), void *param); +struct mevent *mevent_add_disabled(int fd, enum ev_type type, + void (*func)(int, enum ev_type, void *), + void *param); int mevent_enable(struct mevent *evp); int mevent_disable(struct mevent *evp); int mevent_delete(struct mevent *evp); diff --git a/usr.sbin/bhyve/net_backends.c b/usr.sbin/bhyve/net_backends.c index 41f1b267901..36ac7ccf69f 100644 --- a/usr.sbin/bhyve/net_backends.c +++ b/usr.sbin/bhyve/net_backends.c @@ -220,7 +220,7 @@ tap_init(struct net_backend *be, const char *devname, errx(EX_OSERR, "Unable to apply rights for sandbox"); #endif - priv->mevp = mevent_add(be->fd, EVF_READ, cb, param); + priv->mevp = mevent_add_disabled(be->fd, EVF_READ, cb, param); if (priv->mevp == NULL) { WPRINTF(("Could not register event\n")); goto error; @@ -432,7 +432,7 @@ netmap_init(struct net_backend *be, const char *devname, priv->cb_param = param; be->fd = priv->nmd->fd; - priv->mevp = mevent_add(be->fd, EVF_READ, cb, param); + priv->mevp = mevent_add_disabled(be->fd, EVF_READ, cb, param); if (priv->mevp == NULL) { WPRINTF(("Could not register event\n")); return (-1); diff --git a/usr.sbin/bhyve/pci_e82545.c b/usr.sbin/bhyve/pci_e82545.c index 8cf4c48885a..c63676eb313 100644 --- a/usr.sbin/bhyve/pci_e82545.c +++ b/usr.sbin/bhyve/pci_e82545.c @@ -2351,6 +2351,8 @@ e82545_init(struct vmctx *ctx, struct pci_devinst *pi, char *opts) net_genmac(pi, sc->esc_mac.octet); } + netbe_rx_enable(sc->esc_be); + /* H/w initiated reset */ e82545_reset(sc, 0); diff --git a/usr.sbin/bhyve/pci_virtio_net.c b/usr.sbin/bhyve/pci_virtio_net.c index 5e021d1681a..de09dd9b607 100644 --- a/usr.sbin/bhyve/pci_virtio_net.c +++ b/usr.sbin/bhyve/pci_virtio_net.c @@ -101,7 +101,6 @@ struct pci_vtnet_softc { net_backend_t *vsc_be; - int vsc_rx_ready; int resetting; /* protected by tx_mtx */ uint64_t vsc_features; /* negotiated features */ @@ -156,7 +155,6 @@ pci_vtnet_reset(void *vsc) pthread_mutex_lock(&sc->tx_mtx); } - sc->vsc_rx_ready = 0; sc->rx_merge = 1; sc->rx_vhdrlen = sizeof(struct virtio_net_rxhdr); @@ -180,30 +178,29 @@ pci_vtnet_rx(struct pci_vtnet_softc *sc) int len, n; uint16_t idx; - if (!sc->vsc_rx_ready) { - /* - * The rx ring has not yet been set up. - * Drop the packet and try later. - */ - netbe_rx_discard(sc->vsc_be); - return; - } - - /* - * Check for available rx buffers - */ vq = &sc->vsc_queues[VTNET_RXQ]; - if (!vq_has_descs(vq)) { + for (;;) { /* - * No available rx buffers. Drop the packet and try later. - * Interrupt on empty, if that's negotiated. + * Check for available rx buffers. */ - netbe_rx_discard(sc->vsc_be); - vq_endchains(vq, /*used_all_avail=*/1); - return; - } + if (!vq_has_descs(vq)) { + /* No rx buffers. Enable RX kicks and double check. */ + vq_kick_enable(vq); + if (!vq_has_descs(vq)) { + /* + * Still no buffers. Interrupt if needed + * (including for NOTIFY_ON_EMPTY), and + * disable the backend until the next kick. + */ + vq_endchains(vq, /*used_all_avail=*/1); + netbe_rx_disable(sc->vsc_be); + return; + } + + /* More rx buffers found, so keep going. */ + vq_kick_disable(vq); + } - do { /* * Get descriptor chain. */ @@ -215,7 +212,8 @@ pci_vtnet_rx(struct pci_vtnet_softc *sc) if (len <= 0) { /* * No more packets (len == 0), or backend errored - * (err < 0). Return unused available buffers. + * (err < 0). Return unused available buffers + * and stop. */ vq_retchain(vq); /* Interrupt if needed/appropriate and stop. */ @@ -225,10 +223,8 @@ pci_vtnet_rx(struct pci_vtnet_softc *sc) /* Publish the info to the guest */ vq_relchain(vq, idx, (uint32_t)len); - } while (vq_has_descs(vq)); + } - /* Interrupt if needed, including for NOTIFY_ON_EMPTY. */ - vq_endchains(vq, /*used_all_avail=*/1); } /* @@ -254,13 +250,11 @@ pci_vtnet_ping_rxq(void *vsc, struct vqueue_info *vq) struct pci_vtnet_softc *sc = vsc; /* - * A qnotify means that the rx process can now begin + * A qnotify means that the rx process can now begin. */ pthread_mutex_lock(&sc->rx_mtx); - if (sc->vsc_rx_ready == 0) { - sc->vsc_rx_ready = 1; - vq_kick_disable(vq); - } + vq_kick_disable(vq); + netbe_rx_enable(sc->vsc_be); pthread_mutex_unlock(&sc->rx_mtx); } -- 2.45.0