On Wed, May 30, 2018 at 12:44:29AM -0700, okaya@xxxxxxxxxxxxxx wrote: > On 2018-05-30 00:37, Christoph Hellwig wrote: > > On Tue, May 29, 2018 at 09:41:33PM -0700, Sinan Kaya wrote: > > > Bjorn and I discussed the need for such a "safe" mode feature when you > > > want to bring up PCI for a platform. You want to turn off everything > > > as > > > a starter and just stick to bare minimum. > > > > Can we please make it a config option the instead of adding code > > to every kernel? Also maybe the bringup should be in the name > > to make this more clear? > > One other requirement was to have a runtime option rather than compile time > option. > > When someone reported a problem, we wanted to be able to say "use this > option and see if system boots" without doing any bisects or recompilation. > > This would be the first step in troubleshooting a system to see if > fundamental features are working. > > I don't mind changing the name > Bjorn mentioned safe option. I made it safemode. I am looking at Bjorn for > suggestions at this moment. This *was* my idea, but I'm starting to think it was a bad idea. I don't want people to use pci= parameters as the normal way to get a system to boot. That would be a huge support hassle (putting things in release notes, diagnosing problems when people forget it, etc). But the parameters *are* useful for debugging. If we had a "pci=safemode" and it avoided some problem, the next step would be to narrow it down by using the more specific flags (pci=nomsi, pci=noari, pci=no_ext_tags, etc). So I think 95% of the value is in the specific flags, and a "pci=safemode" might add a little bit of value but at the cost of a small but nagging maintenance concern and code clutter. Bjorn
