linux-kernel - Re: [PATCH] firmware: export x86_64 platform flash bios region via sysfs

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Date:   Thu, 11 Nov 2021 15:54:22 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Hans-Gert Dahmen <hans-gert.dahmen@...u.ne>
Cc:     Richard Hughes <hughsient@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Mauro Lima <mauro.lima@...ypsium.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Philipp Deppenwiese <philipp.deppenwiese@...u.ne>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH] firmware: export x86_64 platform flash bios region via sysfs

On Thu, Nov 11, 2021 at 2:56 PM Hans-Gert Dahmen
<hans-gert.dahmen@...u.ne> wrote:
>
> Am Do., 11. Nov. 2021 um 13:46 Uhr schrieb Andy Shevchenko
> <andy.shevchenko@...il.com>:
> >
> > On Thu, Nov 11, 2021 at 1:46 PM Richard Hughes <hughsient@...il.com> wrote:
> > > On Thu, 11 Nov 2021 at 10:33, Mika Westerberg
> > > <mika.westerberg@...ux.intel.com> wrote:
> >
> > > it's always going to work on x64 -- if the system firmware isn't available at that offset then the platform just isn't going to boot.
> >
> > Well, it's _usual_ case, but in general the assumption is simply
> > incorrect. Btw, have you checked it on Coreboot enabled platforms?
> > What about bare metal configurations where the bootloader provides
> > services to the OS?
>
> No it is always the case. I suggest you go read your own Intel specs
> and datasheets

Point me out, please, chapters in SDM (I never really read it in full,
it's kinda 10x Bible size). What x86 expects is 16 bytes at the end of
1Mb physical address space that the CPU runs at first.

> before spreading further FUD. I have experienced u-root
> and coreboot developers sitting right next to me in my office and they
> were among the ones suggesting my patch. This is just laughable,
> please stop it Andy.

Yeah, zillion people can't ever make a mistake... I see.

-- 
With Best Regards,
Andy Shevchenko