Andy Lutomirski
2015-Oct-28 05:30 UTC
[PATCH v2 1/3] virtio_net: Stop doing DMA from the stack
From: Andy Lutomirski <luto at amacapital.net> Once virtio starts using the DMA API, we won't be able to safely DMA from the stack. virtio-net does a couple of config DMA requests from small stack buffers -- switch to using dynamically-allocated memory. This should have no effect on any performance-critical code paths. Cc: netdev at vger.kernel.org Cc: "Michael S. Tsirkin" <mst at redhat.com> Cc: virtualization at lists.linux-foundation.org Reviewed-by: Joerg Roedel <jroedel at suse.de> Signed-off-by: Andy Lutomirski <luto at kernel.org> --- Hi Michael and DaveM- This is a prerequisite for the virtio DMA fixing project. It works as a standalone patch, though. Would it make sense to apply it to an appropriate networking tree now? drivers/net/virtio_net.c | 53 ++++++++++++++++++++++++++++++++---------------- 1 file changed, 36 insertions(+), 17 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index d8838dedb7a4..4f10f8a58811 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -976,31 +976,43 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, struct scatterlist *out) { struct scatterlist *sgs[4], hdr, stat; - struct virtio_net_ctrl_hdr ctrl; - virtio_net_ctrl_ack status = ~0; + + struct { + struct virtio_net_ctrl_hdr ctrl; + virtio_net_ctrl_ack status; + } *buf; + unsigned out_num = 0, tmp; + bool ret; /* Caller should know better */ BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)); - ctrl.class = class; - ctrl.cmd = cmd; + buf = kmalloc(sizeof(*buf), GFP_ATOMIC); + if (!buf) + return false; + buf->status = ~0; + + buf->ctrl.class = class; + buf->ctrl.cmd = cmd; /* Add header */ - sg_init_one(&hdr, &ctrl, sizeof(ctrl)); + sg_init_one(&hdr, &buf->ctrl, sizeof(buf->ctrl)); sgs[out_num++] = &hdr; if (out) sgs[out_num++] = out; /* Add return status. */ - sg_init_one(&stat, &status, sizeof(status)); + sg_init_one(&stat, &buf->status, sizeof(buf->status)); sgs[out_num] = &stat; BUG_ON(out_num + 1 > ARRAY_SIZE(sgs)); virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC); - if (unlikely(!virtqueue_kick(vi->cvq))) - return status == VIRTIO_NET_OK; + if (unlikely(!virtqueue_kick(vi->cvq))) { + ret = (buf->status == VIRTIO_NET_OK); + goto out; + } /* Spin for a response, the kick causes an ioport write, trapping * into the hypervisor, so the request should be handled immediately. @@ -1009,7 +1021,11 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, !virtqueue_is_broken(vi->cvq)) cpu_relax(); - return status == VIRTIO_NET_OK; + ret = (buf->status == VIRTIO_NET_OK); + +out: + kfree(buf); + return ret; } static int virtnet_set_mac_address(struct net_device *dev, void *p) @@ -1151,7 +1167,7 @@ static void virtnet_set_rx_mode(struct net_device *dev) { struct virtnet_info *vi = netdev_priv(dev); struct scatterlist sg[2]; - u8 promisc, allmulti; + u8 *cmdbyte; struct virtio_net_ctrl_mac *mac_data; struct netdev_hw_addr *ha; int uc_count; @@ -1163,22 +1179,25 @@ static void virtnet_set_rx_mode(struct net_device *dev) if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX)) return; - promisc = ((dev->flags & IFF_PROMISC) != 0); - allmulti = ((dev->flags & IFF_ALLMULTI) != 0); + cmdbyte = kmalloc(sizeof(*cmdbyte), GFP_ATOMIC); + if (!cmdbyte) + return; - sg_init_one(sg, &promisc, sizeof(promisc)); + sg_init_one(sg, cmdbyte, sizeof(*cmdbyte)); + *cmdbyte = ((dev->flags & IFF_PROMISC) != 0); if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX, VIRTIO_NET_CTRL_RX_PROMISC, sg)) dev_warn(&dev->dev, "Failed to %sable promisc mode.\n", - promisc ? "en" : "dis"); - - sg_init_one(sg, &allmulti, sizeof(allmulti)); + *cmdbyte ? "en" : "dis"); + *cmdbyte = ((dev->flags & IFF_ALLMULTI) != 0); if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX, VIRTIO_NET_CTRL_RX_ALLMULTI, sg)) dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n", - allmulti ? "en" : "dis"); + *cmdbyte ? "en" : "dis"); + + kfree(cmdbyte); uc_count = netdev_uc_count(dev); mc_count = netdev_mc_count(dev); -- 2.4.3
Michael S. Tsirkin
2015-Oct-28 07:07 UTC
[PATCH v2 1/3] virtio_net: Stop doing DMA from the stack
On Tue, Oct 27, 2015 at 10:30:19PM -0700, Andy Lutomirski wrote:> From: Andy Lutomirski <luto at amacapital.net> > > Once virtio starts using the DMA API, we won't be able to safely DMA > from the stack. virtio-net does a couple of config DMA requests > from small stack buffers -- switch to using dynamically-allocated > memory. > > This should have no effect on any performance-critical code paths. > > Cc: netdev at vger.kernel.org > Cc: "Michael S. Tsirkin" <mst at redhat.com> > Cc: virtualization at lists.linux-foundation.org > Reviewed-by: Joerg Roedel <jroedel at suse.de> > Signed-off-by: Andy Lutomirski <luto at kernel.org> > --- > > Hi Michael and DaveM- > > This is a prerequisite for the virtio DMA fixing project. It works > as a standalone patch, though. Would it make sense to apply it to > an appropriate networking tree now? > > drivers/net/virtio_net.c | 53 ++++++++++++++++++++++++++++++++---------------- > 1 file changed, 36 insertions(+), 17 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index d8838dedb7a4..4f10f8a58811 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -976,31 +976,43 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, > struct scatterlist *out) > { > struct scatterlist *sgs[4], hdr, stat; > - struct virtio_net_ctrl_hdr ctrl; > - virtio_net_ctrl_ack status = ~0; > + > + struct { > + struct virtio_net_ctrl_hdr ctrl; > + virtio_net_ctrl_ack status; > + } *buf; > + > unsigned out_num = 0, tmp; > + bool ret; > > /* Caller should know better */ > BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)); > > - ctrl.class = class; > - ctrl.cmd = cmd; > + buf = kmalloc(sizeof(*buf), GFP_ATOMIC); > + if (!buf) > + return false;This is problematic. The command is never retried, the error is propagated to userspace.> + buf->status = ~0; > + > + buf->ctrl.class = class; > + buf->ctrl.cmd = cmd; > /* Add header */ > - sg_init_one(&hdr, &ctrl, sizeof(ctrl)); > + sg_init_one(&hdr, &buf->ctrl, sizeof(buf->ctrl)); > sgs[out_num++] = &hdr; > > if (out) > sgs[out_num++] = out; > > /* Add return status. */ > - sg_init_one(&stat, &status, sizeof(status)); > + sg_init_one(&stat, &buf->status, sizeof(buf->status)); > sgs[out_num] = &stat; > > BUG_ON(out_num + 1 > ARRAY_SIZE(sgs)); > virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC); > > - if (unlikely(!virtqueue_kick(vi->cvq))) > - return status == VIRTIO_NET_OK; > + if (unlikely(!virtqueue_kick(vi->cvq))) { > + ret = (buf->status == VIRTIO_NET_OK); > + goto out; > + } > > /* Spin for a response, the kick causes an ioport write, trapping > * into the hypervisor, so the request should be handled immediately. > @@ -1009,7 +1021,11 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, > !virtqueue_is_broken(vi->cvq)) > cpu_relax(); > > - return status == VIRTIO_NET_OK; > + ret = (buf->status == VIRTIO_NET_OK); > + > +out: > + kfree(buf); > + return ret; > } > > static int virtnet_set_mac_address(struct net_device *dev, void *p) > @@ -1151,7 +1167,7 @@ static void virtnet_set_rx_mode(struct net_device *dev) > { > struct virtnet_info *vi = netdev_priv(dev); > struct scatterlist sg[2]; > - u8 promisc, allmulti; > + u8 *cmdbyte; > struct virtio_net_ctrl_mac *mac_data; > struct netdev_hw_addr *ha; > int uc_count; > @@ -1163,22 +1179,25 @@ static void virtnet_set_rx_mode(struct net_device *dev) > if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX)) > return; > > - promisc = ((dev->flags & IFF_PROMISC) != 0); > - allmulti = ((dev->flags & IFF_ALLMULTI) != 0); > + cmdbyte = kmalloc(sizeof(*cmdbyte), GFP_ATOMIC); > + if (!cmdbyte) > + return;Here the error is ignored, rx mode will be incorrect. OTOH it looks like that's already the case.> > - sg_init_one(sg, &promisc, sizeof(promisc)); > + sg_init_one(sg, cmdbyte, sizeof(*cmdbyte)); > > + *cmdbyte = ((dev->flags & IFF_PROMISC) != 0); > if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX, > VIRTIO_NET_CTRL_RX_PROMISC, sg)) > dev_warn(&dev->dev, "Failed to %sable promisc mode.\n", > - promisc ? "en" : "dis"); > - > - sg_init_one(sg, &allmulti, sizeof(allmulti)); > + *cmdbyte ? "en" : "dis"); > > + *cmdbyte = ((dev->flags & IFF_ALLMULTI) != 0); > if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX, > VIRTIO_NET_CTRL_RX_ALLMULTI, sg)) > dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n", > - allmulti ? "en" : "dis"); > + *cmdbyte ? "en" : "dis"); > + > + kfree(cmdbyte); > > uc_count = netdev_uc_count(dev); > mc_count = netdev_mc_count(dev);How about this instead? Less code, more robust. Warning: untested. If you do like this approach, Tested-by would be appreciated. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index d8838ded..f94ab78 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -140,6 +140,12 @@ struct virtnet_info { /* CPU hot plug notifier */ struct notifier_block nb; + + /* Control VQ buffers: protected by the rtnl lock */ + struct virtio_net_ctrl_hdr ctrl_hdr; + virtio_net_ctrl_ack ctrl_status; + u8 ctrl_promisc; + u8 ctrl_allmulti; }; struct padded_vnet_hdr { @@ -976,31 +982,30 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, struct scatterlist *out) { struct scatterlist *sgs[4], hdr, stat; - struct virtio_net_ctrl_hdr ctrl; - virtio_net_ctrl_ack status = ~0; unsigned out_num = 0, tmp; /* Caller should know better */ BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)); - ctrl.class = class; - ctrl.cmd = cmd; + vi->ctrl_status = ~0; + vi->ctrl_hdr.class = class; + vi->ctrl_hdr.cmd = cmd; /* Add header */ - sg_init_one(&hdr, &ctrl, sizeof(ctrl)); + sg_init_one(&hdr, &vi->ctrl_hdr, sizeof(vi->ctrl_hdr)); sgs[out_num++] = &hdr; if (out) sgs[out_num++] = out; /* Add return status. */ - sg_init_one(&stat, &status, sizeof(status)); + sg_init_one(&stat, &vi->ctrl_status, sizeof(vi->ctrl_status)); sgs[out_num] = &stat; BUG_ON(out_num + 1 > ARRAY_SIZE(sgs)); virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC); if (unlikely(!virtqueue_kick(vi->cvq))) - return status == VIRTIO_NET_OK; + return vi->ctrl_status == VIRTIO_NET_OK; /* Spin for a response, the kick causes an ioport write, trapping * into the hypervisor, so the request should be handled immediately. @@ -1009,7 +1014,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, !virtqueue_is_broken(vi->cvq)) cpu_relax(); - return status == VIRTIO_NET_OK; + return vi->ctrl_status == VIRTIO_NET_OK; } static int virtnet_set_mac_address(struct net_device *dev, void *p) @@ -1151,7 +1156,6 @@ static void virtnet_set_rx_mode(struct net_device *dev) { struct virtnet_info *vi = netdev_priv(dev); struct scatterlist sg[2]; - u8 promisc, allmulti; struct virtio_net_ctrl_mac *mac_data; struct netdev_hw_addr *ha; int uc_count; @@ -1163,22 +1167,22 @@ static void virtnet_set_rx_mode(struct net_device *dev) if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX)) return; - promisc = ((dev->flags & IFF_PROMISC) != 0); - allmulti = ((dev->flags & IFF_ALLMULTI) != 0); + vi->ctrl_promisc = ((dev->flags & IFF_PROMISC) != 0); + vi->ctrl_allmulti = ((dev->flags & IFF_ALLMULTI) != 0); - sg_init_one(sg, &promisc, sizeof(promisc)); + sg_init_one(sg, &vi->ctrl_promisc, sizeof(vi->ctrl_promisc)); if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX, VIRTIO_NET_CTRL_RX_PROMISC, sg)) dev_warn(&dev->dev, "Failed to %sable promisc mode.\n", - promisc ? "en" : "dis"); + vi->ctrl_promisc ? "en" : "dis"); - sg_init_one(sg, &allmulti, sizeof(allmulti)); + sg_init_one(sg, &vi->ctrl_allmulti, sizeof(vi->ctrl_allmulti)); if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX, VIRTIO_NET_CTRL_RX_ALLMULTI, sg)) dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n", - allmulti ? "en" : "dis"); + vi->ctrl_allmulti ? "en" : "dis"); uc_count = netdev_uc_count(dev); mc_count = netdev_mc_count(dev);> -- > 2.4.3
Andy Lutomirski
2015-Oct-29 23:43 UTC
[PATCH v2 1/3] virtio_net: Stop doing DMA from the stack
On Wed, Oct 28, 2015 at 12:07 AM, Michael S. Tsirkin <mst at redhat.com> wrote:> How about this instead? Less code, more robust. > > Warning: untested. If you do like this approach, Tested-by would be > appreciated.I like it. Tested-by: Andy Lutomirski <luto at kernel.org> --Andy
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