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%2Fmails.dpdk.org%2Farchives%2Fdev%2F2019-July%2F137305.html&data=02%7C01%7Cyskoh%40mellanox.com%7Ccd2d2d88786f43d9603708d70448c623%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C636982582929119170&sdata=4xI5tJ9pcVn1ooTwmZ1f0O%2BaY9p%2FL%2F8O23gr2OW7ZpI%3D&reserved=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%7Cyskoh%40mellanox.com%7Ccd2d2d88786f43d9603708d70448c623%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C636982582929119170&sdata=gFYRsOd8RzINShMvMR%2FXFKwV5RHAwThsDrvwnCrDIiQ%3D&reserved=0
Is this RFC still valid, will there be any follow up? If not am marking it as rejected in next a few days.
