> -----Original Message----- > From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com] > Sent: Tuesday, June 21, 2016 2:31 PM > To: Ananyev, Konstantin > Cc: Lu, Wenzhuo; Stephen Hemminger; dev at dpdk.org; Richardson, Bruce; Chen, > Jing D; Liang, Cunming; Wu, Jingjing; Zhang, Helin; > thomas.monjalon at 6wind.com > Subject: Re: [dpdk-dev] [PATCH v6 1/4] lib/librte_ether: support device reset > > On Tue, Jun 21, 2016 at 01:10:40PM +0000, Ananyev, Konstantin wrote: > > > > > > > > > > Hi Konstantin, > > > > > > > Hi Jerin, > > > > > > > > > -----Original Message----- > > > > > From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com] > > > > > Sent: Tuesday, June 21, 2016 9:56 AM > > > > > To: Lu, Wenzhuo > > > > > Cc: Stephen Hemminger; dev at dpdk.org; Ananyev, Konstantin; > > > > > Richardson, Bruce; Chen, Jing D; Liang, Cunming; Wu, Jingjing; > > > Zhang, > > > > > Helin; thomas.monjalon at 6wind.com > > > > > Subject: Re: [dpdk-dev] [PATCH v6 1/4] lib/librte_ether: support > > > > > device reset > > > > > > > > > > On Tue, Jun 21, 2016 at 08:24:36AM +0000, Lu, Wenzhuo wrote: > > > > > > Hi Jerin, > > > > > > > > > > Hi Wenzhuo, > > > > > > > > > > > > > > > > On Mon, Jun 20, 2016 at 02:24:27PM +0800, Wenzhuo Lu > > > > > > > > > > > wrote: > > > > > > > > > > > > Add an API to reset the device. > > > > > > > > > > > > It's for VF device in this scenario, kernel PF + DPDK > > > > > > > > > > > > VF. > > > > > > > > > > > > When the PF port down->up, APP should call this API to > > > > > > > > > > > > reset > > > > > > > > > > > > VF port. Most likely, APP should call it in its > > > > > > > > > > > > management > > > > > > > > > > > > thread and guarantee the thread safe. It means APP > > > > > > > > > > > > should stop > > > > > > > > > > > > the rx/tx and the device, then reset the device, then > > > > > > > > > > > > recover > > > > > > > > > > > > the device and rx/tx. > > > > > > > > > > > > > > > > > > > > > > Following is _a_ use-case for Device reset. But may be > > > > > > > > > > > not be > > > > > > > > > > > _the_ use case. IMO, We need to first say expected > > > > > > > > > > > behavior of > > > > > > > > > > > this API and add a use-case later. > > > > > > > > > > > > > > > > > > > > > > Other use-case would be, PCIe VF with functional level > > > > > > > > > > > reset for > > > > > > > > > > > SRIOV migration. > > > > > > > > > > > Are we on same page? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > In my experience with Linux devices, this is normally > > > > > > > > > > handled by > > > > > > > > > > the device driver in the start routine. Since any use case > > > > > > > > > > which > > > > > > > > > > needs this is going to do a stop/reset/start sequence, why > > > > > > > > > > not > > > > > > > > > > just have the VF device driver do this in the start > > > > > > > > > > routine?. > > > > > > > > > > > > > > > > > > > > Adding yet another API and state transistion if not > > > > > > > > > > necessary > > > > > > > > > > increases the complexity and required test cases for all > > > > > > > > > > devices. > > > > > > > > > > > > > > > > > > I agree with Stephen here.I think if application needs to > > > > > > > > > call start > > > > > > > > > after the device reset then we could add this logic in start > > > > > > > > > itself > > > > > > > > > rather exposing a yet another API > > > > > > > > Do you mean changing the device_start to include all these > > > > > > > > actions, stop > > > > > > > device -> stop queue -> re-setup queue -> start queue -> start > > > > > > > device ? > > > > > > > > > > > > > > What was the expected API call sequence when you were introduced > > > > > > > this API? > > > > > > > > > > > > > > Point was to have implicit device reset in the API call > > > > > > > sequence(Wherever make > > > > > > > sense for specific PMD) > > > > > > I think the API call sequence depends on the implementation of the > > > > > > APP. Let's say if there's not this reset API, APP can use > this > > > API > > > > > call sequence to handle the PF link down/up event, rte_eth_dev_close > > > > > -> rte_eth_rx_queue_setup -> > rte_eth_tx_queue_setup - > > > > > > > > > rte_eth_dev_start. > > > > > > Actually our purpose is to use this reset API instead of the API > > > > > > call sequence. You can see the reset API is not necessary. The > > > benefit > > > > > is to save the code for APP. > > > > > > > > > > Then I am bit confused with original commit log description. > > > > > | > > > > > |It means APP should stop the rx/tx and the device, then reset the > > > > > |device, then recover the device and rx/tx. > > > > > | > > > > > I was under impression that it a low level reset API for this device? > > > > > Is > > > > > n't it? > > > > > > > > > > The other issue is generalized outlook of the API, Certain PMD will > > > > > not > > > > > have PF link down/up event? Link down/up and only connected to VF and > > > > > PF > > > > > only for configuration. > > > > > > > > > > How about fixing it more transparently in PMD driver itself as > > > > > PMD driver knows the PF link up/down event, Is it possible to > > > > > recover the VF on that event if its only matter of resetting it? > > > > > > > > I think we already went through that discussion on the list. > > > > Unfortunately with current dpdk design it is hardly possible. > > > > To achieve that we need to introduce some sort of synchronisation > > > > between IO and control APIs (locking or so). > > > > Actually I am not sure why having a special reset function will be a > > > > problem. > > > > > > | > > > |It means APP should stop the rx/tx and the device, then reset the > > > |device, then recover the device and rx/tx. > > > | > > > Just to understand, If application still need to do the stop then what > > > value addtion reset API brings on the table? > > > > If application calls dev_reset() it doesn't need to call dev_stop() before > > it. > > dev_reset() will take care of it. > > But it needs to make sure that no other thread will try to modify that > > device state > > (either dev_stop/start, or eth_rx_busrst/eth_tx_burst) while the reset op > > is in place. > > OK. This description looks different than commit log and API doxygen comment. > Please fix it. > How about a different name for this API. Device reset is too generic? > > > > > > > > > > > > > Yes, it would exist only for VFs, for PF it could be left unimplemented. > > > > Though it definitely seems more convenient from user point of view, > > > > they would know: to handle VF reset event, they just need to call that > > > > particular function, not to re-implement their own. > > > What if driver returns "not implemented" then application will have do > > > generic rte_eth_dev_stop/rte_eth_dev_start. > > >That way in application perspective we are NOT solving any problem. > > > > True, but as I said for PF application would just never receive such event. > What is this event ? Is it VF Link up/down event? > > No I was referring to VF itself, Other VF PMD drivers in drivers/net > where this callback is not implemented.
Hmm, the only suggestion I have here - Maintainers/developers of non-Intel PMD will implement it for their VFs? In case of course they do need to handle similar event. if not I suppose there is no harm to left it unimplemented. Konstantin
