On Wed, May 15, 2019 at 05:38:02PM +0800, Liuyixian (Eason) wrote: > > > On 2019/5/9 18:50, Liuyixian (Eason) wrote: > > > > > > On 2019/5/2 21:03, Jason Gunthorpe wrote: > >> On Tue, Apr 30, 2019 at 04:27:41PM +0800, Liuyixian (Eason) wrote: > >>> > >>> > >>> On 2019/4/27 5:05, Leon Romanovsky wrote: > >>>> On Fri, Apr 26, 2019 at 11:36:56AM -0300, Jason Gunthorpe wrote: > >>>>> On Fri, Apr 26, 2019 at 06:12:11PM +0800, Liuyixian (Eason) wrote: > >>>>> > >>>>>> However, I have talked with our chip team about function clear > >>>>>> functionality. We think it is necessary to inform the chip to > >>>>>> perform the outstanding task and some cleanup work and restore > >>>>>> hardware resources in time when rmmod ko. Otherwise, it is > >>>>>> dangerous to reuse the hardware as it can not guarantee those > >>>>>> work can be done well without the notification from our driver. > >>>>> > >>>>> If it is dangerous to reuse the hardware then you have to do this > >>>>> cleanup on device startup, not on device removal. > >>>> > >>>> Right, I can think about gazillion ways to brick such HW. > >>>> The simplest way will be to call SysRq during RDMA traffic > >>>> and no cleanup function will be called in such case. > >>>> > >>>> Thanks > >>> > >>> Hi Jason and Leon, > >>> > >>> As hip08 is a fake pcie device, we could not disassociate and stop the hardware access > >>> through the chain break mechanism as a real pcie device. Alternatively, function clear > >>> is used as a notification to the hardware to stop accessing and ensure to not read or > >>> write DDR later. That is, the role of function clear to hip08 is similar as the chain > >>> break to pcie device. > >> > >> What? This hardware is broken and doesn't respond to the bus master > >> enable bit in the PCI config space?? > >> > > Hi Jason, > > > > Sorry to reply to you late. > > > > Yes, the bus master enable bit should be set by a pcie device when startup and removal. > > The hns (nic) module use it as well. However, we couldn't use/operate this bit in hip08 > > as it shares the PF(physical function) with nic. Therefore, we need function clear to > > notify the hardware to do the cleanup thing and cache write back. > > > > Thanks. > > > > Hi Jason and Leon, > > Do you have further more suggestions? The approach seems completely wrong to me - no other driver is doing something so sketchy. You need to explain why hns is so special Jason
