> > 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. > > > > 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. I suppose it is possible to implement one for PF too, I just don't see much point - as probably no-one will ever use it. Konstantin
