Messages in this thread | | | Subject | Re: [RFC net-next 1/2] ethtool: add support for controling the type of adaptive coalescing | From | tanhuazhong <> | Date | Fri, 20 Nov 2020 09:52:10 +0800 |
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On 2020/11/20 6:02, Michal Kubecek wrote: > On Thu, Nov 19, 2020 at 04:56:42PM +0800, tanhuazhong wrote: >> On 2020/11/19 12:15, Andrew Lunn wrote: >>>> diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h >>>> index 9ca87bc..afd8de2 100644 >>>> --- a/include/uapi/linux/ethtool.h >>>> +++ b/include/uapi/linux/ethtool.h >>>> @@ -433,6 +433,7 @@ struct ethtool_modinfo { >>>> * a TX interrupt, when the packet rate is above @pkt_rate_high. >>>> * @rate_sample_interval: How often to do adaptive coalescing packet rate >>>> * sampling, measured in seconds. Must not be zero. >>>> + * @use_dim: Use DIM for IRQ coalescing, if adaptive coalescing is enabled. >>>> * >>>> * Each pair of (usecs, max_frames) fields specifies that interrupts >>>> * should be coalesced until >>>> @@ -483,6 +484,7 @@ struct ethtool_coalesce { >>>> __u32 tx_coalesce_usecs_high; >>>> __u32 tx_max_coalesced_frames_high; >>>> __u32 rate_sample_interval; >>>> + __u32 use_dim; >>>> }; >>> >>> You cannot do this. >>> >>> static noinline_for_stack int ethtool_set_coalesce(struct net_device *dev, >>> void __user *useraddr) >>> { >>> struct ethtool_coalesce coalesce; >>> int ret; >>> >>> if (!dev->ethtool_ops->set_coalesce) >>> return -EOPNOTSUPP; >>> >>> if (copy_from_user(&coalesce, useraddr, sizeof(coalesce))) >>> return -EFAULT; >>> >>> An old ethtool binary is not going to set this extra last byte to >>> anything meaningful. You cannot tell if you have an old or new user >>> space, so you have no idea if it put anything into use_dim, or if it >>> is random junk. > > Even worse, as there is no indication of data length, ETHTOOL_GCOALESCE > ioctl request from old ethtool on new kernel would result in kernel > writing past the end of userspace buffer. > >>> You have to leave the IOCTL interface unchanged, and limit this new >>> feature to the netlink API. >>> >> >> Hi, Andrew. >> thanks for pointing out this problem, i will fix it. >> without callling set_coalesce/set_coalesce of ethtool_ops, do you have any >> suggestion for writing/reading this new attribute to/from the driver? add a >> new field in net_device or a new callback function in ethtool_ops seems not >> good. > > We could use a similar approach as struct ethtool_link_ksettings, e.g. > > struct kernel_ethtool_coalesce { > struct ethtool_coalesce base; > /* new members which are not part of UAPI */ > } > > get_coalesce() and set_coalesce() would get pointer to struct > kernel_ethtool_coalesce and ioctl code would be modified to only touch > the base (legacy?) part. >
Thanks for your suggestion. i will implement it in V2.
> While already changing the ops arguments, we could also add extack > pointer, either as a separate argument or as struct member (I slightly > prefer the former). > > BtW, please don't forget to update the message descriptions in > Documentation/networking/ethtool-netlink.rst > > Michal >
will update the doc in V2.
Thanks. Huazhong.
> . >
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