linux-kernel - Re: 5.16-rc: "x86/boot: Pull up cmdline" breaks mem=

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Message-ID: <788e766-d391-addf-1d96-e27e35fa574d@google.com>
Date:   Thu, 9 Dec 2021 09:25:30 -0800 (PST)
From:   Hugh Dickins <hughd@...gle.com>
To:     Borislav Petkov <bp@...en8.de>
cc:     Hugh Dickins <hughd@...gle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Anjaneya Chagam <anjaneya.chagam@...el.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Mike Rapoport <rppt@...nel.org>
Subject: Re: 5.16-rc: "x86/boot: Pull up cmdline" breaks mem=

On Thu, 9 Dec 2021, Borislav Petkov wrote:
> 
> Can you pls send me full dmesg and .config of the -rc1 kernel which
> still boots fine. I'd like to try to repro.

I see the action is now happening over in jdorminy's thread, thanks
for the Cc there, I'll look out for developments on that thread.

I judge that you guys understand it better by now, more thought
needed, but my dmesg and config just be noise at this stage; but of
course my testing can help when you've settled on a candidate to try.

So I'll skip sending dmesg and config now: but ask me again if they
would still be useful.

(I see efi issues prompted the failing commit: one of my machines is
legacy booted and CONFIG_EFI is not set, another is UEFI booted and
CONFIG_EFI=y: "mem=1G" is ineffective on both.)

> Next question: does it boot without having supplied "mem=" on the kernel
> cmdline?

No problem with booting whatsoever, mem=1G or not: boots fine, the problem
is just that "mem=1G" is ignored, and I'm given 8G or 16G or whatever the
machine has.

> 
> And just to make sure I understand correctly: this is 64-bit or 32-bit
> kernel?

64-bit kernel.  Until you asked, I assumed 32-bit kernel would behave
the same, but no: I just tried, and the 32-bit kernel respects "mem=1G"
as it should.

Hugh