On Fri, Jul 16 2021, Jason Wang <[email protected]> wrote: > 在 2021/7/15 下午5:16, Stefan Hajnoczi 写道: >> Stopping >> devices sequentially increases migration downtime, so I think the >> interface should encourage concurrently stopping multiple devices. >> >> I think you and Cornelia discussed that an interrupt could be added to >> solve this problem. That would address my concerns about the STOP bit. > > > The problems are: > > 1) if we generate an interrupt after STOP, it breaks the STOP semantic > where the device should not generate any interrupt > 2) if we generate an interrupt before STOP, we may end up with race > conditions
I think not all interrupts are created equal here. For virtqueue notification interrupts, I agree. If the device is being stopped, no notification interrupts will be generated. For device interrupts in the general sense, banning these would make it impossible to implement STOP for CCW, as any channel program (be it RESET, READ_STATUS, or any new one) is required to generate a status pending/interrupt when it is finished. I also don't see how that would create a race condition for CCW. Why can't we simply have an interrupt indicating completion of the STOP request, and no further interrupts after that? --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
