RE: [PATCH v12 00/16] Introduce support for Dell SMBIOS over WMI

[<Mario.Limonciello@dell.com>]

> -----Original Message-----
> From: Darren Hart [mailto:dvhart@infradead.org]
> Sent: Friday, November 3, 2017 4:01 PM
> To: Limonciello, Mario <Mario_Limonciello@Dell.com>
> Cc: andy.shevchenko@gmail.com; linux-kernel@vger.kernel.org; platform-driver-
> x86@vger.kernel.org; luto@kernel.org; quasisec@google.com;
> pali.rohar@gmail.com; rjw@rjwysocki.net; mjg59@google.com; hch@lst.de;
> greg@kroah.com; gnomes@lxorguk.ukuu.org.uk
> Subject: Re: [PATCH v12 00/16] Introduce support for Dell SMBIOS over WMI
> 
> On Fri, Nov 03, 2017 at 04:30:13PM +0000, Mario.Limonciello@dell.com wrote:
> > > -----Original Message-----
> > > From: Darren Hart [mailto:dvhart@infradead.org]
> > > Sent: Thursday, November 2, 2017 7:50 PM
> > > To: Limonciello, Mario <Mario_Limonciello@Dell.com>
> > > Cc: Andy Shevchenko <andy.shevchenko@gmail.com>; LKML <linux-
> > > kernel@vger.kernel.org>; platform-driver-x86@vger.kernel.org; Andy
> Lutomirski
> > > <luto@kernel.org>; quasisec@google.com; pali.rohar@gmail.com;
> > > rjw@rjwysocki.net; mjg59@google.com; hch@lst.de; Greg KH
> <greg@kroah.com>;
> > > Alan Cox <gnomes@lxorguk.ukuu.org.uk>
> > > Subject: Re: [PATCH v12 00/16] Introduce support for Dell SMBIOS over WMI
> > >
> > > On Wed, Nov 01, 2017 at 02:25:21PM -0500, Mario Limonciello wrote:
> > > > The existing way that the dell-smbios helper module and associated
> > > > other drivers (dell-laptop, dell-wmi) communicate with the platform
> > > > really isn't secure.  It requires creating a buffer in physical
> > > > DMA32 memory space and passing that to the platform via SMM.
> > > >
> > > > Since the platform got a physical memory pointer, you've just got
> > > > to trust that the platform has only modified (and accessed) memory
> > > > within that buffer.
> > > >
> > > > Dell Platform designers recognize this security risk and offer a
> > > > safer way to communicate with the platform over ACPI.  This is
> > > > in turn exposed via a WMI interface to the OS.
> > > >
> > > > When communicating over WMI-ACPI the communication doesn't occur
> > > > with physical memory pointers.  When the ASL is invoked, the fixed
> > > > length ACPI buffer is copied to a small operating region.  The ASL
> > > > will invoke the SMI, and SMM will only have access to this operating
> > > > region.  When the ASL returns the buffer is copied back for the OS
> > > > to process.
> > > >
> > > > This method of communication should also deprecate the usage of the
> > > > dcdbas kernel module and software dependent upon it's interface.
> > > > Instead offer a character device interface for communicating with this
> > > > ASL method to allow userspace to use instead.
> > > >
> > > > To faciliate that this patch series introduces a generic way for WMI
> > > > drivers to be able to create discoverable character devices with
> > > > a predictable IOCTL interface through the WMI bus when desired.
> > > > Requiring WMI drivers to explicitly ask for this functionality will
> > > > act as an effective vendor whitelist to character device creation.
> > > >
> > > > Some of this work is the basis for what will be a proper interpreter
> > > > of MOF in the kernel and controls for what drivers will be able to
> > > > do with that MOF.
> > > >
> > > > NOTE: This patch series is intended to go on top of platform-drivers-x86
> > > > linux-next.
> > > >
> > > > For convenience the entire series including those is also available here:
> > > > https://github.com/dell/linux/tree/wmi-smbios
> > >
> > > Queued for testing, thanks Mario.
> > >
> > > --
> > > Darren Hart
> > > VMware Open Source Technology Center
> >
> > Thanks Darren.  BTW Did you forget to push?  I didn't see it at the testing branch:
> > http://git.infradead.org/users/dvhart/linux-platform-drivers-
> x86.git/shortlog/refs/heads/testing
> >
> > Thanks,
> >
> 
> The workflow currently goes first to review-dvhart, which 0-day will pull from,
> then to testing for integration, then to for-next. I plan to move it to testing
> today.

Gotcha, thanks.