On Wed, Jun 6, 2012 at 5:03 PM, Khalid Aziz <khalid.aziz@xxxxxx> wrote: > On Wed, 2012-06-06 at 14:16 -0600, Myron Stowe wrote: >> Hay Khalid, >> >> I've been following this discussion but still do not understand what the >> perceived correct fix is for the situation you were originally trying to >> circumvent - namely, stopping NIC devices from triggering DMA activity >> upon receipt of an incoming packet. >> >> From the discussion it sounds like a driver, upon shutdown, can end >> all active I/O >> clearing the I/O queue, and also (?) shut down its DMA engine, and may >> also go as far as disabling the Bus Master bit. >> >> What was occurring in the original issue - was the driver in question not >> shutting down its DMA engine for some, possibly valid, reason? >> >> Thanks, >> Myron > > Hi Myron, > > The last driver issue with kexec was reported on kexec mailing list in > July of last year and that was with qla driver. From what H Peter Anvin > described, the driver left DMA engine running. > > For the issue I found on an ia64 platform, it was so many years ago that > you are now taxing my old and decrepit memory :) Yeah, if it was more than a couple of weeks ago then I'm likely to have forgotten myself. If you can find it great but don't spend too much time digging. I just wanted some validation of my understanding - o That drivers must consider both "active I/O" and "DMA" (when shutting down), o That the Bus Master disablement was trying to compensate for a driver not quiescing "DMA" as it probably should have (I wasn't sure if these were separate capabilities and/or if there was possibly a valid reason for a driver leaving "DMA" in an enabled state upon shutdown - i.e. Wake on LAN or something similar). Myron > I am digging through > old internal bug reports and will let you know once I find that original > bug report. > > ==================================================================== > Khalid Aziz Unix Systems Lab > (970)898-9214 Hewlett-Packard > khalid.aziz@xxxxxx Fort Collins, CO > -- 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
