On Thu, Apr 13, 2017 at 8:55 AM, <Mario.Limonciello@xxxxxxxx> wrote: > > >> -----Original Message----- >> From: Andy Lutomirski [mailto:luto@xxxxxxxxxx] >> Sent: Thursday, April 13, 2017 10:33 AM >> To: Michał Kępień <kernel@xxxxxxxxxx> >> Cc: Darren Hart <dvhart@xxxxxxxxxxxxx>; Rafael Wysocki <rjw@xxxxxxxxxxxxx>; >> Len Brown <len.brown@xxxxxxxxx>; Pali Rohár <pali.rohar@xxxxxxxxx>; Corentin >> Chary <corentin.chary@xxxxxxxxx>; Limonciello, Mario >> <Mario_Limonciello@xxxxxxxx>; Andy Lutomirski <luto@xxxxxxxxxx>; Andy >> Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>; LKML <linux- >> kernel@xxxxxxxxxxxxxxx>; platform-driver-x86@xxxxxxxxxxxxxxx; linux- >> pm@xxxxxxxxxxxxxxx >> Subject: Re: RFC: WMI Enhancements >> >> On Thu, Apr 13, 2017 at 12:32 AM, Michał Kępień <kernel@xxxxxxxxxx> wrote: >> >> Hi All, >> >> >> >> There are a few parallel efforts involving the Windows Management >> >> Instrumentation (WMI)[1] and dependent/related drivers. I'd like to >> >> have a round of discussion among those of you that have been involved >> >> in this space before we decide on a direction. >> >> >> >> The WMI support in the kernel today fairly narrowly supports a >> >> handful of systems. Andy L. has a work-in-progress series [2] which >> >> converts wmi into a platform device and a proper bus, providing >> >> devices for dependent drivers to bind to, and a mechanism for sibling devices to >> communicate with each other. >> >> I've reviewed the series and feel like the approach is sound, I plan >> >> to carry this series forward and merge it (with Andy L's permission). >> >> >> >> Are there any objections to this? >> > >> > Back in January 2016, I sent Andy a few minor comments about this >> > series. A year later, I offered to iron out the remaining issues and >> > resubmit the series in Andy's name when I find the time. Sadly, >> > things have changed a bit for me since that time and it is unlikely >> > that I will be able to deliver, for which I am sorry. >> > >> > However, browsing Andy's branch I see that most issues have been >> > resolved, though I think some of my remarks [1] have either been >> > missed or silently refuted :) >> > >> > Anyway, I also like this approach and I think this series is a >> > valuable cleanup. >> >> Me too :) >> >> >> In Windows, applications interact with WMI more or less directly. We >> >> don't do this in Linux currently, although it has been discussed in >> >> the past [3]. Some vendors will work around this by performing >> >> SMI/SMM, which is inefficient at best. Exposing WMI methods to >> >> userspace would bring parity to WMI for Linux and Windows. >> >> >> >> There are two principal concerns I'd appreciate your thoughts on: >> >> >> >> a) As an undiscoverable interface (you need to know the method >> >> signatures ahead of time), universally exposing every WMI "device" to >> >> userspace seems like "a bad idea" from a security and stability >> >> perspective. While access would certainly be privileged, it seems >> >> more prudent to make this exposure opt-in. We also handle some of >> >> this with kernel drivers and exposing those "devices" to userspace >> >> would enable userspace and the kernel to fight over control. So - if >> >> we expose WMI devices to userspace, I believe this should be done on >> >> a case by case basis, opting in, and not by default as part of the >> >> WMI driver (although it can provide the mechanism for a sub-driver to use), and >> possibly a devmode to do so by default. >> >> I agree. I don't want too see gnome-whatever-widget talking directly to WMI and >> confusing the kernel driver for the same thing. > > So there are plenty of other things that can be done by WMI that don't > really make sense to live in the kernel, particularly on what Dell exposes via > WMI. > > If the desire of this group ends up being to not expose WMI by default, > I'd like to at least propose it be exposed for the GUID's Dell is using. Is it just the "call SMBIOS" GUID or are there other things? > > Perhaps as part of changing dell-smbios to use WMI, also extend it's > functionality to userspace. > Could this still result in userspace and the kernel fighting over control of various bits of the system? If so, that's a bit less than ideal.
