2022-05-11 13:04:33

by Jason Wang

Subject: Re: [PATCH] vdpa: Warn if MTU configured is too low

On Wed, May 11, 2022 at 4:48 PM Eli Cohen <[email protected]> wrote:
>
> Following the recommendation in virio spec 1.1, a device offering
> VIRTIO_NET_F_MTU should set the mtu to at least 1280 bytes.
>
> Print a warning if this recommendation is not met.
>
> Signed-off-by: Eli Cohen <[email protected]>

I wonder why it's a must?

> ---
> drivers/vdpa/vdpa.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 91f4c13c7c7c..961168fe9094 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -583,6 +583,9 @@ vdpa_nl_cmd_mgmtdev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
> BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) | \
> BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP))
>
> +/* Recommended virtio spec 1.1 section 5.1.4.1 */
> +#define VIRTIO_MIN_PREFERRED_MTU 1280
> +
> static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *info)
> {
> struct vdpa_dev_set_config config = {};
> @@ -634,6 +637,10 @@ static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *i
> err = PTR_ERR(mdev);
> goto err;
> }
> + if ((mdev->supported_features & BIT_ULL(VIRTIO_NET_F_MTU)) &&
> + (config.mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) &&
> + config.net.mtu < VIRTIO_MIN_PREFERRED_MTU))

Should be <= ?

Thanks

> + pr_warn("MTU is below recommended value\n");
> if ((config.mask & mdev->config_attr_mask) != config.mask) {
> NL_SET_ERR_MSG_MOD(info->extack,
> "All provided attributes are not supported");
> @@ -1135,7 +1142,7 @@ static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
> [VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
> [VDPA_ATTR_DEV_NET_CFG_MACADDR] = NLA_POLICY_ETH_ADDR,
> /* virtio spec 1.1 section 5.1.4.1 for valid MTU range */
> - [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, 68),
> + [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, ETH_MIN_MTU),
> };
>
> static const struct genl_ops vdpa_nl_ops[] = {
> --
> 2.35.1
>

2022-05-11 14:46:54

by Eli Cohen

Subject: RE: [PATCH] vdpa: Warn if MTU configured is too low

> From: Jason Wang <[email protected]>
> Sent: Wednesday, May 11, 2022 12:34 PM
> To: Eli Cohen <[email protected]>
> Cc: mst <[email protected]>; virtualization <[email protected]>; linux-kernel <[email protected]>; Si-
> Wei Liu <[email protected]>
> Subject: Re: [PATCH] vdpa: Warn if MTU configured is too low
>
> On Wed, May 11, 2022 at 4:48 PM Eli Cohen <[email protected]> wrote:
> >
> > Following the recommendation in virio spec 1.1, a device offering
> > VIRTIO_NET_F_MTU should set the mtu to at least 1280 bytes.
> >
> > Print a warning if this recommendation is not met.
> >
> > Signed-off-by: Eli Cohen <[email protected]>
>
> I wonder why it's a must?

It's definitely not a must but I thought if the spec says "should" it deserves a warning
but we can drop this if you think the warning is not in place.

>
> > ---
> > drivers/vdpa/vdpa.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> > index 91f4c13c7c7c..961168fe9094 100644
> > --- a/drivers/vdpa/vdpa.c
> > +++ b/drivers/vdpa/vdpa.c
> > @@ -583,6 +583,9 @@ vdpa_nl_cmd_mgmtdev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
> > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) | \
> > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP))
> >
> > +/* Recommended virtio spec 1.1 section 5.1.4.1 */
> > +#define VIRTIO_MIN_PREFERRED_MTU 1280
> > +
> > static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *info)
> > {
> > struct vdpa_dev_set_config config = {};
> > @@ -634,6 +637,10 @@ static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *i
> > err = PTR_ERR(mdev);
> > goto err;
> > }
> > + if ((mdev->supported_features & BIT_ULL(VIRTIO_NET_F_MTU)) &&
> > + (config.mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) &&
> > + config.net.mtu < VIRTIO_MIN_PREFERRED_MTU))
>
> Should be <= ?

I don't think so. If it equals 1280 you don't want to warn.

>
> Thanks
>
> > + pr_warn("MTU is below recommended value\n");
> > if ((config.mask & mdev->config_attr_mask) != config.mask) {
> > NL_SET_ERR_MSG_MOD(info->extack,
> > "All provided attributes are not supported");
> > @@ -1135,7 +1142,7 @@ static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
> > [VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
> > [VDPA_ATTR_DEV_NET_CFG_MACADDR] = NLA_POLICY_ETH_ADDR,
> > /* virtio spec 1.1 section 5.1.4.1 for valid MTU range */
> > - [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, 68),
> > + [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, ETH_MIN_MTU),
> > };
> >
> > static const struct genl_ops vdpa_nl_ops[] = {
> > --
> > 2.35.1
> >

2022-05-11 15:59:33

by Jason Wang

Subject: Re: [PATCH] vdpa: Warn if MTU configured is too low

On Wed, May 11, 2022 at 6:02 PM Eli Cohen <[email protected]> wrote:
>
> > From: Jason Wang <[email protected]>
> > Sent: Wednesday, May 11, 2022 12:34 PM
> > To: Eli Cohen <[email protected]>
> > Cc: mst <[email protected]>; virtualization <[email protected]>; linux-kernel <[email protected]>; Si-
> > Wei Liu <[email protected]>
> > Subject: Re: [PATCH] vdpa: Warn if MTU configured is too low
> >
> > On Wed, May 11, 2022 at 4:48 PM Eli Cohen <[email protected]> wrote:
> > >
> > > Following the recommendation in virio spec 1.1, a device offering
> > > VIRTIO_NET_F_MTU should set the mtu to at least 1280 bytes.
> > >
> > > Print a warning if this recommendation is not met.
> > >
> > > Signed-off-by: Eli Cohen <[email protected]>
> >
> > I wonder why it's a must?
>
> It's definitely not a must but I thought if the spec says "should" it deserves a warning

Right.

> but we can drop this if you think the warning is not in place.

I remember netlink has an extra log buffer, I wonder if it's better to
warn there?

>
> >
> > > ---
> > > drivers/vdpa/vdpa.c | 9 ++++++++-
> > > 1 file changed, 8 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> > > index 91f4c13c7c7c..961168fe9094 100644
> > > --- a/drivers/vdpa/vdpa.c
> > > +++ b/drivers/vdpa/vdpa.c
> > > @@ -583,6 +583,9 @@ vdpa_nl_cmd_mgmtdev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
> > > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) | \
> > > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP))
> > >
> > > +/* Recommended virtio spec 1.1 section 5.1.4.1 */
> > > +#define VIRTIO_MIN_PREFERRED_MTU 1280
> > > +
> > > static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *info)
> > > {
> > > struct vdpa_dev_set_config config = {};
> > > @@ -634,6 +637,10 @@ static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *i
> > > err = PTR_ERR(mdev);
> > > goto err;
> > > }
> > > + if ((mdev->supported_features & BIT_ULL(VIRTIO_NET_F_MTU)) &&
> > > + (config.mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) &&
> > > + config.net.mtu < VIRTIO_MIN_PREFERRED_MTU))
> >
> > Should be <= ?
>
> I don't think so. If it equals 1280 you don't want to warn.

Yes, you're right.

Thanks

>
> >
> > Thanks
> >
> > > + pr_warn("MTU is below recommended value\n");
> > > if ((config.mask & mdev->config_attr_mask) != config.mask) {
> > > NL_SET_ERR_MSG_MOD(info->extack,
> > > "All provided attributes are not supported");
> > > @@ -1135,7 +1142,7 @@ static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
> > > [VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
> > > [VDPA_ATTR_DEV_NET_CFG_MACADDR] = NLA_POLICY_ETH_ADDR,
> > > /* virtio spec 1.1 section 5.1.4.1 for valid MTU range */
> > > - [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, 68),
> > > + [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, ETH_MIN_MTU),
> > > };
> > >
> > > static const struct genl_ops vdpa_nl_ops[] = {
> > > --
> > > 2.35.1
> > >
>

2022-05-11 16:16:16

by Eli Cohen

Subject: RE: [PATCH] vdpa: Warn if MTU configured is too low

> -----Original Message-----
> From: Jason Wang <[email protected]>
> Sent: Wednesday, May 11, 2022 1:19 PM
> To: Eli Cohen <[email protected]>
> Cc: mst <[email protected]>; virtualization <[email protected]>; linux-kernel <[email protected]>; Si-
> Wei Liu <[email protected]>
> Subject: Re: [PATCH] vdpa: Warn if MTU configured is too low
>
> On Wed, May 11, 2022 at 6:02 PM Eli Cohen <[email protected]> wrote:
> >
> > > From: Jason Wang <[email protected]>
> > > Sent: Wednesday, May 11, 2022 12:34 PM
> > > To: Eli Cohen <[email protected]>
> > > Cc: mst <[email protected]>; virtualization <[email protected]>; linux-kernel <[email protected]>; Si-
> > > Wei Liu <[email protected]>
> > > Subject: Re: [PATCH] vdpa: Warn if MTU configured is too low
> > >
> > > On Wed, May 11, 2022 at 4:48 PM Eli Cohen <[email protected]> wrote:
> > > >
> > > > Following the recommendation in virio spec 1.1, a device offering
> > > > VIRTIO_NET_F_MTU should set the mtu to at least 1280 bytes.
> > > >
> > > > Print a warning if this recommendation is not met.
> > > >
> > > > Signed-off-by: Eli Cohen <[email protected]>
> > >
> > > I wonder why it's a must?
> >
> > It's definitely not a must but I thought if the spec says "should" it deserves a warning
>
> Right.
>
> > but we can drop this if you think the warning is not in place.
>
> I remember netlink has an extra log buffer, I wonder if it's better to
> warn there?
>

You mean use NL_SET_ERR_MSG_MOD(info->extack, "MTU is below recommended value\n") ?
dmesg stays clean but the user gets a warning

> >
> > >
> > > > ---
> > > > drivers/vdpa/vdpa.c | 9 ++++++++-
> > > > 1 file changed, 8 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> > > > index 91f4c13c7c7c..961168fe9094 100644
> > > > --- a/drivers/vdpa/vdpa.c
> > > > +++ b/drivers/vdpa/vdpa.c
> > > > @@ -583,6 +583,9 @@ vdpa_nl_cmd_mgmtdev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
> > > > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) | \
> > > > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP))
> > > >
> > > > +/* Recommended virtio spec 1.1 section 5.1.4.1 */
> > > > +#define VIRTIO_MIN_PREFERRED_MTU 1280
> > > > +
> > > > static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *info)
> > > > {
> > > > struct vdpa_dev_set_config config = {};
> > > > @@ -634,6 +637,10 @@ static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *i
> > > > err = PTR_ERR(mdev);
> > > > goto err;
> > > > }
> > > > + if ((mdev->supported_features & BIT_ULL(VIRTIO_NET_F_MTU)) &&
> > > > + (config.mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) &&
> > > > + config.net.mtu < VIRTIO_MIN_PREFERRED_MTU))
> > >
> > > Should be <= ?
> >
> > I don't think so. If it equals 1280 you don't want to warn.
>
> Yes, you're right.
>
> Thanks
>
> >
> > >
> > > Thanks
> > >
> > > > + pr_warn("MTU is below recommended value\n");
> > > > if ((config.mask & mdev->config_attr_mask) != config.mask) {
> > > > NL_SET_ERR_MSG_MOD(info->extack,
> > > > "All provided attributes are not supported");
> > > > @@ -1135,7 +1142,7 @@ static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
> > > > [VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
> > > > [VDPA_ATTR_DEV_NET_CFG_MACADDR] = NLA_POLICY_ETH_ADDR,
> > > > /* virtio spec 1.1 section 5.1.4.1 for valid MTU range */
> > > > - [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, 68),
> > > > + [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, ETH_MIN_MTU),
> > > > };
> > > >
> > > > static const struct genl_ops vdpa_nl_ops[] = {
> > > > --
> > > > 2.35.1
> > > >
> >

2022-05-12 00:17:27

by Michael S. Tsirkin

Subject: Re: [PATCH] vdpa: Warn if MTU configured is too low

On Wed, May 11, 2022 at 05:34:25PM +0800, Jason Wang wrote:
> On Wed, May 11, 2022 at 4:48 PM Eli Cohen <[email protected]> wrote:
> >
> > Following the recommendation in virio spec 1.1, a device offering
> > VIRTIO_NET_F_MTU should set the mtu to at least 1280 bytes.
> >
> > Print a warning if this recommendation is not met.
> >
> > Signed-off-by: Eli Cohen <[email protected]>
>
> I wonder why it's a must?


It's a SHOULD in the spec. I guess 1280 is to allow IPv6.

> > ---
> > drivers/vdpa/vdpa.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> > index 91f4c13c7c7c..961168fe9094 100644
> > --- a/drivers/vdpa/vdpa.c
> > +++ b/drivers/vdpa/vdpa.c
> > @@ -583,6 +583,9 @@ vdpa_nl_cmd_mgmtdev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
> > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) | \
> > BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP))
> >
> > +/* Recommended virtio spec 1.1 section 5.1.4.1 */
> > +#define VIRTIO_MIN_PREFERRED_MTU 1280
> > +
> > static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *info)
> > {
> > struct vdpa_dev_set_config config = {};
> > @@ -634,6 +637,10 @@ static int vdpa_nl_cmd_dev_add_set_doit(struct sk_buff *skb, struct genl_info *i
> > err = PTR_ERR(mdev);
> > goto err;
> > }
> > + if ((mdev->supported_features & BIT_ULL(VIRTIO_NET_F_MTU)) &&
> > + (config.mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU) &&
> > + config.net.mtu < VIRTIO_MIN_PREFERRED_MTU))
>
> Should be <= ?
>
> Thanks



> > + pr_warn("MTU is below recommended value\n");
> > if ((config.mask & mdev->config_attr_mask) != config.mask) {
> > NL_SET_ERR_MSG_MOD(info->extack,
> > "All provided attributes are not supported");
> > @@ -1135,7 +1142,7 @@ static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
> > [VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
> > [VDPA_ATTR_DEV_NET_CFG_MACADDR] = NLA_POLICY_ETH_ADDR,
> > /* virtio spec 1.1 section 5.1.4.1 for valid MTU range */
> > - [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, 68),
> > + [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, ETH_MIN_MTU),
> > };
> >
> > static const struct genl_ops vdpa_nl_ops[] = {
> > --
> > 2.35.1
> >