linux-kernel - Re: [tip:x86/alternatives] [x86/alternatives] ee8962082a: WARNING:at_arch/x86/kernel/cpu/cpuid-deps.c:#do_clear_cpu

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Date: Wed, 8 May 2024 16:37:42 +0800
From: Oliver Sang <oliver.sang@...el.com>
To: Borislav Petkov <bp@...en8.de>
CC: Sean Christopherson <seanjc@...gle.com>, <oe-lkp@...ts.linux.dev>,
	<lkp@...el.com>, <linux-kernel@...r.kernel.org>, <x86@...nel.org>, "Ingo
 Molnar" <mingo@...nel.org>, Srikanth Aithal <sraithal@....com>,
	<fengwei.yin@...el.com>, <yujie.liu@...el.com>, <oliver.sang@...el.com>
Subject: Re: [tip:x86/alternatives] [x86/alternatives] ee8962082a:
 WARNING:at_arch/x86/kernel/cpu/cpuid-deps.c:#do_clear_cpu_cap

hi, Boris,

On Wed, May 08, 2024 at 10:24:38AM +0200, Borislav Petkov wrote:
> On Wed, May 08, 2024 at 04:08:18PM +0800, Oliver Sang wrote:
> > we really don't do any manual change recently, however, per your reminding,
> > we rerun tests on both ee8962082a and its parent v6.9-rc3 again.
> > 
> > while we made original report, we always saw below for both commits.
> > "x86/cpu: VMX (outside TXT) disabled by BIOS"
> > 
> > by rerun today, we cannot see it again, on both commits.
> 
> Yeah, from the last dump you shouldn't be seeing it.
> 
> > then for ee8962082a, the reported
> >   WARNING:at_arch/x86/kernel/cpu/cpuid-deps.c:#do_clear_cpu_cap
> > disappeared also while no "x86/cpu: VMX (outside TXT) disabled by BIOS"
> 
> Yeah, it does feel like something underneath the OS has changed/is
> changing for this to happen.
> 
> > we are using kexec to boot into kernel, and the kernel images keep same,
> > so we are sure this strage phenomenon is not caused by kernel build.
> 
> Hmm, kexec won't go through BIOS so I can imagine if the kernel has left
> FEAT_CTL in some weird state... but then if it has been locked, nothing
> should change it anymore.
> 
> > now we doubt it's really a bios issue, we found another similar machine,
> > which also show "x86/cpu: VMX (outside TXT) disabled by BIOS", but after
> > several rounds of cold reboot, the message disappeared, too.
> 
> If you see that again, please run my branch with the debug patch - that
> should at least tell us what's weird in FEAT_CTL.

thanks a lot for education! sure, we will do that.

> 
> > we will investigate this BIOS further and avoid this kind of misleading
> > report in the future.
> > 
> > sorry again :(
> 
> No worries, thanks for testing kernels and thanks Sean too. :-)
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette
>