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: Tue, 7 May 2024 15:08:11 +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>,
	<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 Mon, May 06, 2024 at 05:57:59PM +0200, Borislav Petkov wrote:
> On Mon, May 06, 2024 at 08:28:46AM -0700, Sean Christopherson wrote:
> > The only way the WARN could have fired without this series is if VMX is enabled
> > in BIOS on the boot CPU, but disabled by BIOS on one more secondary CPUs.  And
> > _that_ is a bogus setup that (a) the kernel absolutely should WARN about, and
> > (b) _still_ occurs with one or both patches applied.
> 
> Right, that's my suspicion too.
> 
> > So I don't see how this series could possibly have fixed the issue Oliver
> > encountered, nor do I see any value in moving init_ia32_feat_ctl() into
> > early_init_intel().
> 
> Hm, right. I should've done this from the very beginning:
> 
> Oliver, can you please run the below debugging patch *without* any other
> patches ontop of latest Linus master?
> 
> Also pls send /proc/cpuinfo and dmesg.

I applied the debug pach ontop of lastest Linus master:

1621a826233a7 debug patch from Boris for ee8962082a
dccb07f2914cd (HEAD, linus/master) Merge tag 'for-6.9-rc7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

attached dmesg and cpuinfo (a little diff, so I attached it again)

> 
> Thx.
> 
> ---
> diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
> index 1640ae76548f..74d2f0a351aa 100644
> --- a/arch/x86/kernel/cpu/feat_ctl.c
> +++ b/arch/x86/kernel/cpu/feat_ctl.c
> @@ -117,8 +117,14 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
>  	bool tboot = tboot_enabled();
>  	bool enable_vmx;
>  	u64 msr;
> +	int ret;
>  
> -	if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr)) {
> +	ret = rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr);
> +
> +	pr_info("%s: CPU%d: FEAT_CTL: 0x%llx, tboot: %d\n",
> +		__func__, c->cpu_index, msr, tboot);
> +
> +	if (ret) {
>  		clear_cpu_cap(c, X86_FEATURE_VMX);
>  		clear_cpu_cap(c, X86_FEATURE_SGX);
>  		return;
> @@ -165,6 +171,9 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
>  			msr |= FEAT_CTL_SGX_LC_ENABLED;
>  	}
>  
> +	pr_info("%s: CPU%d: Write FEAT_CTL: 0x%llx\n",
> +		__func__, c->cpu_index, msr);
> +
>  	wrmsrl(MSR_IA32_FEAT_CTL, msr);
>  
>  update_caps:
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette
> 

Download attachment "dmesg.xz" of type "application/x-xz" (24916 bytes)

View attachment "cpuinfo-2" of type "text/plain" (66819 bytes)