> -----Original Message----- > From: Yigit, Ferruh <ferruh.yi...@linux.intel.com> > Sent: Tuesday, October 8, 2019 15:57 > To: Yongseok Koh <ys...@mellanox.com>; Adrien Mazarguil > <adrien.mazarg...@6wind.com> > Cc: Shahaf Shuler <shah...@mellanox.com>; Thomas Monjalon > <tho...@monjalon.net>; Ferruh Yigit <ferruh.yi...@intel.com>; Andrew > Rybchenko <arybche...@solarflare.com>; Olivier Matz > <olivier.m...@6wind.com>; dev <dev@dpdk.org>; Slava Ovsiienko > <viachesl...@mellanox.com> > Subject: Re: [dpdk-dev] [PATCH] ethdev: add flow tag > > On 7/11/2019 2:59 AM, Yongseok Koh wrote: > > On Tue, Jul 09, 2019 at 10:38:06AM +0200, Adrien Mazarguil wrote: > >> On Fri, Jul 05, 2019 at 06:05:50PM +0000, Yongseok Koh wrote: > >>>> On Jul 5, 2019, at 6:54 AM, Adrien Mazarguil > <adrien.mazarg...@6wind.com> wrote: > >>>> > >>>> On Thu, Jul 04, 2019 at 04:23:02PM -0700, Yongseok Koh wrote: > >>>>> A tag is a transient data which can be used during flow match. > >>>>> This can be used to store match result from a previous table so > >>>>> that the same pattern need not be matched again on the next table. > >>>>> Even if outer header is decapsulated on the previous match, the match > result can be kept. > >>>>> > >>>>> Some device expose internal registers of its flow processing > >>>>> pipeline and those registers are quite useful for stateful > >>>>> connection tracking as it keeps status of flow matching. Multiple > >>>>> tags are supported by specifying index. > >>>>> > >>>>> Example testpmd commands are: > >>>>> > >>>>> flow create 0 ingress pattern ... / end > >>>>> actions set_tag index 2 value 0xaa00bb mask 0xffff00ff / > >>>>> set_tag index 3 value 0x123456 mask 0xffffff / > >>>>> vxlan_decap / jump group 1 / end > >>>>> > >>>>> flow create 0 ingress pattern ... / end > >>>>> actions set_tag index 2 value 0xcc00 mask 0xff00 / > >>>>> set_tag index 3 value 0x123456 mask 0xffffff / > >>>>> vxlan_decap / jump group 1 / end > >>>>> > >>>>> flow create 0 ingress group 1 > >>>>> pattern tag index is 2 value spec 0xaa00bb value mask 0xffff00ff / > >>>>> eth ... / end > >>>>> actions ... jump group 2 / end > >>>>> > >>>>> flow create 0 ingress group 1 > >>>>> pattern tag index is 2 value spec 0xcc00 value mask 0xff00 / > >>>>> tag index is 3 value spec 0x123456 value mask 0xffffff / > >>>>> eth ... / end > >>>>> actions ... / end > >>>>> > >>>>> flow create 0 ingress group 2 > >>>>> pattern tag index is 3 value spec 0x123456 value mask 0xffffff / > >>>>> eth ... / end > >>>>> actions ... / end > >>>>> > >>>>> Signed-off-by: Yongseok Koh <ys...@mellanox.com> > >>>> > >>>> Hi Yongseok, > >>>> > >>>> Only high level questions for now, while it unquestionably looks > >>>> useful, from a user standpoint exposing the separate index seems > >>>> redundant and not necessarily convenient. Using the following example > to illustrate: > >>>> > >>>> actions set_tag index 3 value 0x123456 mask 0xfffff > >>>> > >>>> pattern tag index is 3 value spec 0x123456 value mask 0xffffff > >>>> > >>>> I might be missing something, but why isn't this enough: > >>>> > >>>> pattern tag index is 3 # match whatever is stored at index 3 > >>>> > >>>> Assuming it can work, then why bother with providing value > >>>> spec/mask on set_tag? A flow rule pattern matches something, sets > >>>> some arbitrary tag to be matched by a subsequent flow rule and > >>>> that's it. It even seems like relying on the index only on both occasions > is enough for identification. > >>>> > >>>> Same question for the opposite approach; relying on the value, > >>>> never mentioning the index. > >>>> > >>>> I'm under the impression that the index is a hardware-specific > >>>> constraint that shouldn't be exposed (especially since it's an > >>>> 8-bit field). If so, a PMD could keep track of used indices without > >>>> having them exposed through the public API. > >>> > >>> > >>> Thank you for review, Adrien. > >>> Hope you are doing well. It's been long since we talked each other. > >>> :-) > >> > >> Yeah clearly! Hope you're doing well too. I'm somewhat busy hence > >> slow to answer these days... > >> > >> <dev@dpdk.org> hey! > >> <dev@dpdk.org> no private talks! > >> > >> Back to the topic: > >> > >>> Your approach will work too in general but we have a request from > >>> customer that they want to partition this limited tag storage. > >>> Assuming that HW exposes 32bit tags (those are 'registers' in HW > >>> pipeline in mlx5 HW). Then, customers want to store multiple data > >>> even in a 32-bit storage. For example, 16bit vlan tag, 8bit table id > >>> and 8bit flow id. As they want to split one 32bit storage, I thought > >>> it is better to provide mask when setting/matching the value. Even > >>> some customer wants to store multiple flags bit by bit like ol_flags. They > do want to alter only partial bits. > >>> > >>> And for the index, it is to reference an entry of tags array as HW > >>> can provide larger registers than 32-bit. For example, mlx5 HW would > >>> provide 4 of 32b storage which users can use for their own sake. > >>> tag[0], tag[1], tag[2], tag[3] > >> > >> OK, looks like I missed the point then. I initially took it for a > >> funky alternative to RTE_FLOW_ITEM_TYPE_META & > >> RTE_FLOW_ACTION_TYPE_SET_META (ingress extended [1]) but while it > >> could be used like that, it's more of a way to temporarily store and > retrieve a small amount of data, correct? > > > > Correct. > > > >> Out of curiosity, are these registers independent from META and other > >> items/actions in mlx5, otherwise what happens if they are combined? > > > > I thought about combining it but I chose this way. Because it is > > transient. META can be set by packet descriptor on Tx and can be > > delivered to host via mbuf on Rx, but this TAG item can't. If I > > combine it, users have to query this capability for each 32b storage. > > And also, there should be a way to request data from such storages > > (i.e. new action , e.g. copy_meta). Let's say there are 4x32b storages > > - meta[4]. If user wants to get one 32b data (meta[i]) out of them to > > mbuf->metadata, it should be something like, > > ingress / pattern .. / > > actions ... set_meta index i data x / copy_meta_to_rx index i And if > > user wants to set meta[i] via mbuf on Tx, > > egress / pattern meta index is i data is x ... / > > actions ... copy_meta_to_tx index i > > > > For sure, user is also responsible for querying these capabilities per > > each meta[] storage. > > > > As copy_meta_to_tx/rx isn't a real action, this example would confuse > user. > > egress / pattern meta index is i data is x ... / > > actions ... copy_meta_to_tx index i > > > > User might misunderstand the order of two things - item meta and > > copy_meta action. I also thought about having capability bits per each > > meta[] storage but it also looked complex. > > > > I do think rte_flow item/action is better to be simple, atomic and > > intuitive. > > That's why I made this choice. > > > >> Are there other uses for these registers? Say, referencing their > >> contents from other places in a flow rule so they don't have to be hard- > coded? > > > > Possible. > > Actually, this feature is needed by connection tracking of OVS-DPDK. > > > >> Right now I'm still uncomfortable with such a feature in the public > >> API because compared to META [1], this approach looks very > >> hardware-specific and seemingly difficult to map on different HW > architectures. > > > > I wouldn't say it is HW-specific. Like I explained above, I just > > define this new item/action to make things easy-to-use and intuitive. > > > >> However, the main problem is that as described, its end purpose seems > >> redundant with META, which I think can cover the use cases you gave. > >> So what can an application do with this that couldn't be done in a > >> more generic fashion through META? > >> > >> I may still be missing something and I'm open to ideas, but assuming > >> it doesn't make it into the public rte_flow API, it remains an > >> interesting feature on its own merit which could be added to DPDK as > >> PMD-specific pattern items/actions [2]. mlx5 doesn't have any yet, > >> but it's pretty common for PMDs to expose a public header that > >> dedicated applications can include to use this kind of features (look for > rte_pmd_*.h, e.g. rte_pmd_ixgbe.h). > >> No problem with that. > > > > That's good info. Thanks. But still considering > > connection-tracking-like use-cases, this transient storage on multi-table > flow pipeline is quite useful. > > > > > > thanks, > > Yongseok > > > >> [1] "[PATCH] ethdev: extend flow metadata" > >> > >> > https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmai > >> ls.dpdk.org%2Farchives%2Fdev%2F2019- > July%2F137305.html&data=02%7C > >> > 01%7Cviacheslavo%40mellanox.com%7Cc0402133b8b2422fc23308d74bef1 > 4fd%7C > >> > a652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C637061362537116332 > &sda > >> > ta=I%2B%2BERHK8FXzLxXkbbjGTmNDf2e%2FsVRvQ%2FIJW4ZmaYrk%3D&a > mp;reserve > >> d=0 > >> > >> [2] "Negative types" > >> > >> > https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoc > >> .dpdk.org%2Fguides%2Fprog_guide%2Frte_flow.html%23negative- > types& > >> > data=02%7C01%7Cviacheslavo%40mellanox.com%7Cc0402133b8b2422fc23 > 308d74 > >> > bef14fd%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C63706136 > 25371163 > >> > 32&sdata=o6hcNuwWnv9fADGxNcy6S9B0xwCNdlNhbloIKRiMiNo%3D& > amp;reser > >> ved=0 > > Is this RFC still valid, will there be any follow up? > If not am marking it as rejected in next a few days.
Yes, RFC is valid, v2 and support in mlx5 Is coming. WBR, Slava
