> -----Original Message----- > From: Richardson, Bruce > Sent: Wednesday, June 6, 2018 1:55 PM > To: Guo, Jia <jia....@intel.com>; techbo...@dpdk.org > Cc: dev@dpdk.org; Ananyev, Konstantin <konstantin.anan...@intel.com>; > step...@networkplumber.org; Yigit, Ferruh > <ferruh.yi...@intel.com>; gaetan.ri...@6wind.com; Wu, Jingjing > <jingjing...@intel.com>; tho...@monjalon.net; > mo...@mellanox.com; ma...@mellanox.com; Van Haaren, Harry > <harry.van.haa...@intel.com>; Zhang, Qi Z > <qi.z.zh...@intel.com>; Zhang, Helin <helin.zh...@intel.com>; > jblu...@infradead.org; shreyansh.j...@nxp.com > Subject: Re: [dpdk-dev] [RFC] hot plug failure handle mechanism > > +Tech-board as I think that this should have more input at the design stage > ahead of any code patches being pushed. > > On Mon, Jun 04, 2018 at 09:56:10AM +0800, Guo, Jia wrote: > > hi,bruce > > > > > > On 5/29/2018 7:20 PM, Bruce Richardson wrote: > > > On Thu, May 24, 2018 at 07:55:43AM +0100, Guo, Jia wrote: > > > <snip> > > > > The hot plug failure handle mechanism should be come across as > > > > bellow: > > > > > > > > 1. Add a new bus ops “handle_hot-unplug”in bus to handle bus > > > > read/write error, it is bus-specific and each > > > > > > > > kind of bus can implement its own logic. > > > > > > > > 2. Implement pci bus specific ops“pci_handle_hot_unplug”, in > > > > the > > > > function, base on the > > > > > > > > failure address to remap memory which belong to the corresponding > > > > device that unplugged. > > > > > > > > 3. Implement a new sigbus handler, and register it when start > > > > device event monitoring, > > > > > > > > once the MMIO sigbus error exposure, it will trigger the above hot > > > > plug > > > > failure handle mechanism, > > > > > > > > that will keep app, that working on packet processing, would not be > > > > broken and crash, then could > > > > > > > > keep going clean, fail-safe or other working task. > > > > > > > > 4. Also also will introduce the solution by use testpmd to show > > > > the example of the whole procedure like that: > > > > > > > > device unplug ->failure handle->stop forwarding->stop port->close > > > > port->detach port. > > > > > > > Hi Jeff, > > > > > > so if I understand this correctly the proposal is that we need two > > > parallel > > > solutions to handle safe removal of a device. > > > > > > 1. We need a solution to support unpluging of the device at the bus level, > > > ie. remove the device from the list of devices and to make access to > > > that device invalid. > > > 2. Since the removal of the device from the software lists is not going to > > > be instantaneous, we need a mechanism to handle any accesses to the > > > device from the data path until such time as the removal is complete. > > > To > > > support that, you propose to add a sigbus handler which will > > > automatically replace any mmio bar mappings with some other memory > > > that is > > > ok to access - presumable zero memory or similar. > > > > > > Is this understanding correct? > > > > i think you are correct about that. > > > > > Point #2 seems reasonably clear to me, but for #1, presumably the trigger > > > to the bus needs to come from the kernel. What is planned to be used > > > there? > > > > about point #1, i should clarify here is that, we will use the device event > > monitor mechanism to detect the hot unplug event. > > the monitor be enabled by app(or fail-safe driver), and app(fail-safe > > driver) register the event callback. Once the hot unplug behave be detected, > > the user's callback could be triggered to let app(fail-safe driver) know the > > event and manage the process, it will call APIs to stop the device > > and detach the device from the bus. > > Ok. If there is no failsafe driver, and the app does not set up a handler, > does nothing happen when we get a removal event? Will the app just crash? > > > > > > You also talk about using testpmd as a reference for this, but you don't > > > explain how an application can be notified of a device removal, or even > > > why > > > that is necessary. Since all applications should now be using the proper > > > macros when iterating device lists, and not just assuming devices 0-N are > > > valid, what changes would you see a normal app having to make to be > > > hotplug-safe? > > > > we could use app or fail-safe driver to use these mechanism , but at this > > stage i will firstly use testpmd as a reference. > > as above reply, testpmd should enable device event mechanism to monitor the > > device removal, and register callback, > > the device bdf list is managed by bus and the hoplug fail handler will be > > process by the eal layer, then the app would be hotplug-safe. > > > > is there anything i miss to clarify? please shout. and i think i will detail > > more later. > > This is becoming clearer now, thanks. Just the one question above I have at > this point. > Given how long-running this issue of hotplug is, I'm hoping others on the > technical board can also review this proposal.
I looked at the actual code a bit for 18.05. It seems ok to me in general, though I provided few comments regarding particular implementation details. Konstantin
