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Date: Fri, 30 Oct 2015 14:55:30 +0100
From: Christian Borntraeger <borntraeger@...ibm.com>
To: Andy Lutomirski <luto@...nel.org>, linux-kernel@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>, sparclinux@...r.kernel.org
Cc: Joerg Roedel <jroedel@...e.de>,
Cornelia Huck <cornelia.huck@...ibm.com>,
Sebastian Ott <sebott@...ux.vnet.ibm.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Christoph Hellwig <hch@....de>, benh@...nel.crashing.org,
KVM <kvm@...r.kernel.org>, dwmw2@...radead.org,
Martin Schwidefsky <schwidefsky@...ibm.com>,
linux-s390 <linux-s390@...r.kernel.org>,
"Michael S. Tsirkin" <mst@...hat.com>,
virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v4 1/6] virtio-net: Stop doing DMA from the stack
Am 30.10.2015 um 02:09 schrieb Andy Lutomirski:
> From: "Michael S. Tsirkin" <mst@...hat.com>
>
> 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.
>
> [I wrote the subject and commit message. mst wrote the code. --luto]
>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> signed-off-by: Michael S. Tsirkin <mst@...hat.com>
I still get an error when using multiqueue:
# ethtool -L eth0 combined 4
[ 33.534686] virtio_ccw 0.0.000d: DMA-API: device driver maps memory from stack [addr=00000000629e7c06]
[ 33.534704] ------------[ cut here ]------------
[ 33.534705] WARNING: at lib/dma-debug.c:1169
[ 33.534706] Modules linked in: dm_multipath
[ 33.534709] CPU: 1 PID: 1087 Comm: ethtool Not tainted 4.3.0-rc3+ #269
[ 33.534710] task: 00000000616f9978 ti: 00000000629e4000 task.ti: 00000000629e4000
[ 33.534712] Krnl PSW : 0704d00180000000 00000000005869d2 (check_for_stack+0xb2/0x118)
[ 33.534716] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 EA:3
Krnl GPRS: 000000000000006a 0000000000d60f44 000000000000005a 0000000064ee0870
[ 33.534718] 00000000005869ce 0000000000000000 0000000000000001 00000000629e7c06
[ 33.534719] 0000000000000000 0000000000000c06 0000000000000002 000000006467f800
[ 33.534720] 0000000064673428 00000000629e7c06 00000000005869ce 00000000629e7928
[ 33.534726] Krnl Code: 00000000005869c2: c0200024ad4e larl %r2,a1c45e
00000000005869c8: c0e5ffe6d6fc brasl %r14,2617c0
#00000000005869ce: a7f40001 brc 15,5869d0
>00000000005869d2: c010003465eb larl %r1,c135a8
00000000005869d8: e31010000012 lt %r1,0(%r1)
00000000005869de: a784000a brc 8,5869f2
00000000005869e2: e340f0b00004 lg %r4,176(%r15)
00000000005869e8: ebcff0a00004 lmg %r12,%r15,160(%r15)
[ 33.534736] Call Trace:
[ 33.534737] ([<00000000005869ce>] check_for_stack+0xae/0x118)
[ 33.534738] [<0000000000586e3c>] debug_dma_map_page+0x114/0x160
[ 33.534740] [<00000000005a31f8>] vring_map_one_sg.isra.7+0x98/0xc0
[ 33.534742] [<00000000005a3b72>] virtqueue_add_sgs+0x1e2/0x788
[ 33.534744] [<0000000000618afc>] virtnet_send_command+0xcc/0x140
[ 33.534745] [<0000000000618c0c>] virtnet_set_queues+0x9c/0x110
[ 33.534747] [<0000000000619928>] virtnet_set_channels+0x78/0xe0
[ 33.534748] [<00000000006f63ea>] ethtool_set_channels+0x62/0x88
[ 33.534750] [<00000000006f8900>] dev_ethtool+0x10d8/0x1a48
[ 33.534752] [<000000000070c540>] dev_ioctl+0x190/0x510
[ 33.534754] [<00000000006cf2da>] sock_do_ioctl+0x7a/0x90
[ 33.534755] [<00000000006cf840>] sock_ioctl+0x1e8/0x2d0
[ 33.534758] [<00000000002e6c78>] do_vfs_ioctl+0x3a8/0x508
[ 33.534759] [<00000000002e6e7c>] SyS_ioctl+0xa4/0xb8
[ 33.534762] [<00000000008231ec>] system_call+0x244/0x264
[ 33.534763] [<000003ff922026d2>] 0x3ff922026d2
[ 33.534764] Last Breaking-Event-Address:
[ 33.534765] [<00000000005869ce>] check_for_stack+0xae/0x118
[ 33.534766] ---[ end trace 2379df65f4decfc4 ]---
> ---
> drivers/net/virtio_net.c | 34 +++++++++++++++++++---------------
> 1 file changed, 19 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d8838dedb7a4..f94ab786088f 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);
>
--
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