On 12/09/2016 02:44 PM, Linas Vepstas wrote: > On Fri, Dec 9, 2016 at 2:37 PM, Cao jin <caoj.fnst@xxxxxxxxxxxxxx> wrote: >> >> >> On 12/09/2016 02:24 PM, Linas Vepstas wrote: >>> I suppose I'm confused, but I recall that link resets are non-fatal. >>> Fatal errors typically require that the the pci adapter be completely >>> reset, any adapter firmware to be reloaded from scratch, the device >>> driver has to kill all device state and start from scratch. Its huge. >>> If the fatal error is on pci device that is under a block device >>> holding a file system, then (usually) there is no way to recover, >>> because the block layer (and file system) cannot deal with a block >>> device that disappeared and then reappeared some few seconds later. >>> (maybe some future zfs or lvm or btrfs might be able to deal with >>> this, but not today) >>> >>> By contrast, link resets are far more gentle: the device driver might >>> have to discard some half-full FIFO's, or cancel some in-flight >>> commands, but can otherwise gracefully recover without telling the >>> higher layers that there were any problems. >>> >>> --linas >>> >> >> I am little confused too, even not sure if we are talking the same >> *fatal error*, I am talking the fatal error defined in PCI Express spec, >> chapter 6.2.2.2.1: >> >> Fatal errors are uncorrectable error conditions which render the >> particular Link and related hardware unreliable. For Fatal errors, a >> reset of the components on the Link may be required to return to >> reliable operation. Platform handling of Fatal errors, and any efforts >> to limit the effects of these errors, is platform implementation specific. >> >> Link reset means set *secondary bus reset* bit in pci bridge config >> space, can reset the link and device simultaneously, is the strongest >> kind of reset as I know. > > OK, well, its been far too many years, and I don't have the PCI spec > at my fingertips. > Isn't there a link reset that can be performed, without forcing a device reset? > At least I don't find the exact words saying that. -- Sincerely, Cao jin > The intent was that some PCI link errors are due to vibration, > ground-bounce, humidity, etc. and that these errors can be detected > and do not corrupt the device state or the device driver state. Since > they are not associated with data corruption (or rather, the > corruption is local to the link), these can be recovered by reseting > just the link, without resetting the whole adapter. They may require > reseting some device-driver state, but not all of it. > > However, this was all decided before the PCI-E spec was written, so > maybe the newer PCI-E specs now say something different. > > --linas > >> >>> On Thu, Dec 8, 2016 at 10:13 PM, Cao jin <caoj.fnst@xxxxxxxxxxxxxx> wrote: >>>> >>>> >>>> On 12/08/2016 10:05 PM, Jonathan Corbet wrote: >>>>> On Thu, 8 Dec 2016 16:16:14 +0800 >>>>> Cao jin <caoj.fnst@xxxxxxxxxxxxxx> wrote: >>>>> >>>>>> The platform resets the link, and then calls the link_reset() callback >>>>>> on all affected device drivers. This is a PCI-Express specific state >>>>>> -and is done whenever a non-fatal error has been detected that can be >>>>>> +and is done whenever a fatal error has been detected that can be >>>>>> "solved" by resetting the link. This call informs the driver of the >>>>> >>>>> As far as I can tell, the original text was correct here; why do you >>>>> think this change needs to be made? >>>>> >>>> >>>> See do_recovery() in aer core, reset_link() is called only seeing fatal >>>> error. >>>> >>>> -- >>>> Sincerely, >>>> Cao jin >>>> >>>> >>> >>> >>> >> >> -- >> Sincerely, >> Cao jin >> >> > > > . > -- 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
