linux-kernel - Re: [LSF/MM] CXL Boot to Bash - Section 1: BIOS, EFI, and Early Boot

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Message-ID: <Z7ddtZBHx28_HIPR@gourry-fedora-PF4VCD3F>
Date: Thu, 20 Feb 2025 11:52:05 -0500
From: Gregory Price <gourry@...rry.net>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: lsf-pc@...ts.linux-foundation.org, linux-mm@...ck.org,
	linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [LSF/MM] CXL Boot to Bash - Section 1: BIOS, EFI, and Early Boot

On Thu, Feb 20, 2025 at 04:30:43PM +0000, Jonathan Cameron wrote:
> 
> > 
> > Example CEDT Entries (truncated) 
> >          Subtable Type : 00 [CXL Host Bridge Structure]
> >               Reserved : 00
> >                 Length : 0020
> > Associated host bridge : 00000005
> > 
> >          Subtable Type : 01 [CXL Fixed Memory Window Structure]
> >               Reserved : 00
> >                 Length : 002C
> >               Reserved : 00000000
> >    Window base address : 000000C050000000
> >            Window size : 0000003CA0000000
> > 
> > If this memory is NOT marked "Special Purpose" by BIOS (next section),
> 
> Specific purpose.  You don't want to know how long that term took to
> agree on...
>

Oh man how'd i muck that up.  Thanks for the correction.

I suppose I can/should re-issue all of these with corrections
accordingly.  Maybe even convert this into a documentation somewhere

:sweat:

> > you should find a matching entry EFI Memory Map and /proc/iomem
> > 
> > BIOS-e820:   [mem 0x000000c050000000-0x000000fcefffffff] usable
> 
> Trivial but that's not the EFI memory map, that's the e820.
> On some architectures this really will be coming from the EFI memory map.
> 

You're right, though on my system they're equivalent, just plucked the
wrong thing out of dmesg.  Will correct.

~Gregory