On Tue, Oct 4, 2011 at 8:06 AM, Avi Kivity <avi@xxxxxxxxxx> wrote: > On 10/04/2011 11:46 AM, Avi Kivity wrote: >> >> On 10/03/2011 05:12 PM, Jon Mason wrote: >>> >>> PCI: Workaround for Intel MPS errata >>> >>> Intel 5000 and 5100 series memory controllers have a known issue if >>> read >>> completion coalescing is enabled (the default setting) and the PCI-E >>> Maximum Payload Size is set to 256B. To work around this issue, >>> disable >>> read completion coalescing if the MPS is 256B. >>> >>> It is worth noting that there is no function to undo the disable of >>> read >>> completion coalescing, and the performance benefit of read completion >>> coalescing will be lost if the MPS is set from 256B to 128B. It is >>> only >>> possible to have this issue via hotplug removing the only 256B MPS >>> device in the system (thus making all of the other devices in the >>> system >>> have a performance degradation without the benefit of any 256B >>> transfers). Therefore, this trade off is acceptable. >>> >>> >>> http://www.intel.com/content/dam/doc/specification-update/5000-chipset-memory-controller-hub-specification-update.pdf >>> >>> http://www.intel.com/content/dam/doc/specification-update/5100-memory-controller-hub-chipset-specification-update.pdf >>> >>> Thanks to Jesse Brandeburg and Ben Hutchings for providing insight >>> into >>> the problem. >>> >>> Reported-by: Avi Kivity<avi@xxxxxxxxxx> >>> Signed-off-by: Jon Mason<mason@xxxxxxxx> >>> >>> + >>> + if (!(val& (1<< 10))) { >>> + done = true; >>> + return; >>> + } >> >> Here, you bail out if bit 10 is clear. So if we're here, it's set. >> >>> + >>> + val |= (1<< 10); >> >> Now it's even more set? >> > > Even with this line changed to clear bit 10, I still get a hard lockup. Do That stinks, thanks for finding that issue and fixing it. > we need to clear this bit on the other 5000 devices? I notice they have > similar values in word 0x48, with bits 10 set in them. > > What does "Device 7-2,0" refer to in the workaround description? Seems to > me we need to apply the workaround to the PCIe ports as well. I have no idea what that means, but it would make sense. I'll modify the patch to do this as well. Thanks for being so much help :) > > -- > error compiling committee.c: too many arguments to function > > -- > 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 > -- 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
