(2012/09/11 23:43), Vivek Goyal wrote: > On Tue, Sep 11, 2012 at 07:32:35PM +0900, Takao Indoh wrote: > > [..] >> I'll post new patch which clears bus master bit and resets devices in >> second kernel. >> >> As to the boot parameter to enable this function, you suggested using >> reset_devices. I found that on a certain platform resetting devices >> caused PCIe error due to a hardware bug. Therefore I think we need >> new parameter apart from reset_devices to disable this function on >> such a machine. > > Can you explain a bit more how the error happens. I still don't think > that because of a bug in a platform somewhere we should be introducing > a separate command line parameter and not reuse the exisiting one. Also > you have not explained what's the bug and how a new parameter will > avoid the bug. The bug I mentioned is that ACS Violation occurs at PCIe switch when reading PCI configuration after device reset. I got information that this violation is caused by PCIe switch bug. The machine becomes fatal status by this error. The reason why I try to introduce new parameter is that I want to avoid regression by this patch. Let's say this patch was included in kernel and its reset function was enabled by reset_devices as you said. AFAIK reset_devices is always needed for kdump, so it means that devices are always reset at kdump boot time. It causes a regression that system always becomes abnormal status when we run kdump on the machine which has a bug I mentioned. To avoid this regression, I want to separate reset_devices from this reset function. Or how about this? - if user specify reset_devices, devices are reset by this patch, as you said. - To avoid a regression I said, add new parameter like "pci=noreset". If this parameter is specified, the reset function I add is disabled and we can avoid regression. Thanks, Takao Indoh
