linux-kernel - Re: [PATCH v3 3/5] x86/microcode: Avoid any chance of MCE's during microcode update

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Message-ID: <Yvyfi9XC8bu0cOG+@gmail.com>
Date:   Wed, 17 Aug 2022 09:58:03 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Ashok Raj <ashok.raj@...el.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        LKML Mailing List <linux-kernel@...r.kernel.org>,
        X86-kernel <x86@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Tom Lendacky <thomas.lendacky@....com>,
        Jacon Jun Pan <jacob.jun.pan@...el.com>
Subject: Re: [PATCH v3 3/5] x86/microcode: Avoid any chance of MCE's during
 microcode update


* Ingo Molnar <mingo@...nel.org> wrote:

> > +void mce_set_mcip(void)
> > +{
> > +	mce_wrmsrl(MSR_IA32_MCG_STATUS, 0x1);
> > +}
> > +
> > +void mce_clear_mcip(void)
> > +{
> > +	mce_wrmsrl(MSR_IA32_MCG_STATUS, 0x0);
> > +}
> 
> Instead of naming new APIs after how they are doing stuff, please name them 
> after *what* they are doing at the highest level: they disable/enable MCEs.
> 
> Ie. I'd suggest something like:
> 
>      mce_disable()
>      mce_enable()
> 
> I'd also suggest to at minimum add a WARN_ON_ONCE() if MSR_IA32_MCG_STATUS 
> is already 1 when we disable it - because whoever wanted it disabled will 
> now be surprised by us enabling them again.

Also, Boris tells me that writing 0x0 to MSR_IA32_MCG_STATUS apparently 
shuts the platform down - which is not ideal...

Thanks,

	Ingo