On Mon, Jul 06, 2020 at 06:59:32PM -0700, Dan Williams wrote: > The runtime firmware activation capability of Intel NVDIMM devices > requires memory transactions to be disabled for 100s of microseconds. > This timeout is large enough to cause in-flight DMA to fail and other > application detectable timeouts. Arrange for firmware activation to be > executed while the system is "quiesced", all processes and device-DMA > frozen. > > It is already required that invoking device ->freeze() callbacks is > sufficient to cease DMA. A device that continues memory writes outside > of user-direction violates expectations of the PM core to be to > establish a coherent hibernation image. > > That said, RDMA devices are an example of a device that access memory > outside of user process direction. RDMA drivers also typically assume > the system they are operating in will never be hibernated. A solution > for RDMA collisions with firmware activation is outside the scope of > this change and may need to rely on being able to survive the platform > imposed memory controller quiesce period. Yikes. I don't think we should support such a broken runtime firmware activation.
