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Date: Wed, 19 Nov 2014 17:21:46 +0800
From: Jason Wang <jasowang@...hat.com>
To: Cornelia Huck <cornelia.huck@...ibm.com>
CC: rusty@...tcorp.com.au, mst@...hat.com,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
Wanlong Gao <gaowanlong@...fujitsu.com>
Subject: Re: [PATCH V2 net] virtio-net: validate features during probe
On 11/19/2014 04:54 PM, Cornelia Huck wrote:
> On Wed, 19 Nov 2014 15:21:29 +0800
> Jason Wang <jasowang@...hat.com> wrote:
>
>> This patch validates feature dependencies during probe and fail the probing
>> if a dependency is missed. This fixes the issues of hitting BUG()
>> when qemu fails to advertise features correctly. One example is booting
>> guest with ctrl_vq=off through qemu.
>>
>> Cc: Rusty Russell <rusty@...tcorp.com.au>
>> Cc: Michael S. Tsirkin <mst@...hat.com>
>> Cc: Cornelia Huck <cornelia.huck@...ibm.com>
>> Cc: Wanlong Gao <gaowanlong@...fujitsu.com>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>> Changes from V1:
>> - Drop VIRTIO_NET_F_*_UFO from the checklist, since it was disabled
>> ---
>> drivers/net/virtio_net.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 91 insertions(+)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index ec2a8b4..b16a761 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1673,6 +1673,93 @@ static const struct attribute_group virtio_net_mrg_rx_group = {
>> };
>> #endif
>>
>> +static int virtnet_validate_features(struct virtio_device *dev,
>> + unsigned int *table,
>> + int table_size,
>> + unsigned int feature)
>> +{
>> + int i;
>> +
>> + if (!virtio_has_feature(dev, feature)) {
> Do an early return, get rid of one indentation level?
This sounds good.
>> + for (i = 0; i < table_size; i++) {
>> + unsigned int f = table[i];
>> +
>> + if (virtio_has_feature(dev, f)) {
>> + dev_err(&dev->dev,
>> + "buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x was not",
> s/hyperviser/hypervisor/ (also below)
Yes, thanks for the catching.
>
>> + f, feature);
>> + return -EINVAL;
>> + }
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int virtnet_check_features(struct virtio_device *dev)
>> +{
>> + unsigned int features_for_ctrl_vq[] = {
>> + VIRTIO_NET_F_CTRL_RX,
>> + VIRTIO_NET_F_CTRL_VLAN,
>> + VIRTIO_NET_F_GUEST_ANNOUNCE,
>> + VIRTIO_NET_F_MQ,
>> + VIRTIO_NET_F_CTRL_MAC_ADDR
>> + };
>> + unsigned int features_for_guest_csum[] = {
>> + VIRTIO_NET_F_GUEST_TSO4,
>> + VIRTIO_NET_F_GUEST_TSO6,
>> + VIRTIO_NET_F_GUEST_ECN,
>> + };
>> + unsigned int features_for_host_csum[] = {
>> + VIRTIO_NET_F_HOST_TSO4,
>> + VIRTIO_NET_F_HOST_TSO6,
>> + VIRTIO_NET_F_HOST_ECN,
>> + };
> I'm wondering whether it would be easier to read if you listed all
> prereqs per feature instead of all features that depend on a feature?
> It would still be hard to express the v4/v6 or conditions below in
> tables, though.
For v4 and v6, we could use something like
unsigned int feature_for_host_tso6[] = {
VIRTIO_NET_F_HOST_ECN,
};
unsigned int feature_for_host_tso4[] = {
VIRTIO_NET_F_HOST_ECN,
}
To avoid the following open-coding for ECN. And probably we need another
device specific dependency table and let virtio core do this instead.
>
> Or call the arrays features_depending_on_foo?
Yes.
>
>> + int err;
>> +
>> + err = virtnet_validate_features(dev, features_for_ctrl_vq,
>> + ARRAY_SIZE(features_for_ctrl_vq),
>> + VIRTIO_NET_F_CTRL_VQ);
>> + if (err)
>> + return err;
> If you already print a message that a user may use to fix their
> hypervisor (or bug someone about it), would it make sense to check all
> dependencies and print a full list of everything that is broken in the
> advertised feature bits? I usually hate it if I fix one thing only to
> hit the next bug when the program could have already told me about
> everything I need to fix :)
>
Right this sounds good.
>> +
>> + err = virtnet_validate_features(dev, features_for_guest_csum,
>> + ARRAY_SIZE(features_for_guest_csum),
>> + VIRTIO_NET_F_GUEST_CSUM);
>> + if (err)
>> + return err;
>> +
>> + err = virtnet_validate_features(dev, features_for_host_csum,
>> + ARRAY_SIZE(features_for_host_csum),
>> + VIRTIO_NET_F_CSUM);
>> + if (err)
>> + return err;
>> +
>> + if (virtio_has_feature(dev, VIRTIO_NET_F_GUEST_ECN) &&
>> + (!virtio_has_feature(dev, VIRTIO_NET_F_GUEST_TSO4) ||
>> + !virtio_has_feature(dev, VIRTIO_NET_F_GUEST_TSO6))) {
>> + dev_err(&dev->dev,
>> + "buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x or 0x%x was not",
>> + VIRTIO_NET_F_GUEST_ECN,
>> + VIRTIO_NET_F_GUEST_TSO4,
>> + VIRTIO_NET_F_GUEST_TSO6);
>> + return -EINVAL;
>> + }
>> +
>> + if (virtio_has_feature(dev, VIRTIO_NET_F_HOST_ECN) &&
>> + (!virtio_has_feature(dev, VIRTIO_NET_F_HOST_TSO4) ||
>> + !virtio_has_feature(dev, VIRTIO_NET_F_HOST_TSO6))) {
>> + dev_err(&dev->dev,
>> + "buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x or 0x%x was not",
> "Hypervisor bug: advertised feature <foo> but not <bar> or <baz>"
>
> ?
More compact, looks good. Thanks
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