From mboxrd@z Thu Jan 1 00:00:00 1970 From: josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org Subject: Re: [PATCH] x86/efi-bgrt: Switch pr_err() to pr_debug() for invalid BGRT Date: Mon, 29 Jun 2015 07:45:42 -0700 Message-ID: <20150629144542.GA794@cloud> References: <1435579602-6612-1-git-send-email-matt@codeblueprint.co.uk> <20150629131305.GB13113@pd.tnic> <20150629140022.GA22374@x> <20150629141724.GG12383@pd.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20150629141724.GG12383-fF5Pk5pvG8Y@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Borislav Petkov Cc: Matt Fleming , Tom Yan , Matthew Garrett , linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Matt Fleming List-Id: linux-efi@vger.kernel.org On Mon, Jun 29, 2015 at 04:17:24PM +0200, Borislav Petkov wrote: > On Mon, Jun 29, 2015 at 07:00:22AM -0700, Josh Triplett wrote: > > Definitely not FW_BUG. The field is reserved *now*; it would be > > legitimate for a new version of the BGRT spec to define one of those > > bits for something else. > > Which would mean that booting old kernels on new FW which defines those > reserved bits would cause that warning to fire erroneously. Not erroneously; those bits could potentially indicate some status condition we don't know about, so we need to assume we can't handle the table if a bit we don't understand is set. (Specs like this should really do what ext4 does, and define whether a given set of currently undefined bits are optional or mandatory; as in, if you don't understand them, can you proceed or should you stop?) > So then we probably don't need it at all or we need to check implemented > BGRT version of the FW running to know which bits are defined by the > spec and which are reserved... > > Also, does the spec really say that reserved bits must be zero? Or it > doesn't specify their value? The spec says those bits of the status field are reserved and must be zero. - Josh Triplett