Hi all, Following questions can be of naïve nature. Kindly, help me to clarify the points. Thanks in Advance. 1) Consider a situation where a PCIe device has requested a DMA Write operation followed by an MSI based interrupt. Upon receiving the interrupt, the software will read/check the DMAed data. Now, even if the device is guaranteeing the ordering between the two (issuing one after the other), whether the I/O controller OR chipset can reorder/buffer them? This may result into getting interrupt before the data is DMAed resulting into software reading invalid data. Here data is residing into internal buffers of I/O controller and CPU is trying to read from memory. Whether such DMA reordering can happen/is allowed at all? Whether I/O controller can employ such intelligence(any kind of DMA reordering) for gaining some performance advantage? Mainly, focus is on high-end server class platforms having 8 or 16 cores with many peripherals. 2) If above situation is at all possible, then to avoid such situation is the responsibility of the device or the driver for that device? Mainly, both the components (device and driver) expected to be generic in nature (platform, I/O controller independent). 3) In continuation, if driver has to handle such situations, then how to handle such cases in Linux device driver? Any API is there for pending DMA flush/sync in I/O controller? I am aware of rmb(), wmb() & mb() which ensures ordering from CPU side i.e. slave read/writes. Anythings similar for DMA operations ? Kindly, update me if i am missing something. Any info,link or reference will be of great help. Thanks and Regards, Yogeshwar -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
