linux-kernel - Re: [RESEND RFC PATCH] x86/bugs: Add "unknown" reporting for MMIO Stale Data

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Date:   Fri, 29 Jul 2022 19:40:22 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Tony Luck <tony.luck@...el.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        antonio.gomez.iglesias@...ux.intel.com,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        andrew.cooper3@...rix.com, Josh Poimboeuf <jpoimboe@...nel.org>
Subject: Re: [RESEND RFC PATCH] x86/bugs: Add "unknown" reporting for MMIO
 Stale Data

On Fri, Jul 29, 2022 at 04:07:36PM -0700, Tony Luck wrote:
> On Fri, Jul 29, 2022 at 03:54:58PM -0700, Dave Hansen wrote:
> > On 7/29/22 14:46, Pawan Gupta wrote:
> > > Let me see if there is a way to distinguish between 4. and 5. below:
> > > 
> > >    CPU category				  X86_BUG_MMIO_STALE_DATA	X86_BUG_MMIO_UNKNOWN
> > > -----------------------------------------------------------------------------------------------
> > > 1. Known affected (in cpu list)			1				0
> > > 2. CPUs with HW immunity (MMIO_NO=1)		0				0
> > > 3. Other vendors				0				0
> > > 4. Older Intel CPUs				0				1
> > > 5. Not affected current CPUs (but MMIO_NO=0)	0				?
> > 
> > This seems like something we would need to go back to our colleagues to
> > figure out.  Basically, at the time of publishing the
> > X86_BUG_MMIO_STALE_DATA papers, what was considered "older"?
> > 
> > In other words, we need the folks at Intel that did this good work to
> > _show_ their work (at least part of it).
> 
> https://www.intel.com/content/www/us/en/developer/topic-technology/software-security-guidance/processors-affected-consolidated-product-cpu-model.html
> 
> Click to the 2022 tab. The MMIO affected/not-affected status is there
> (you'll need to use the horizontal scroll to shift over to see those
> columns).
> 
> This table lists all the CPUs that were not "older".
> 
> Any CPU not on that list is out of servicing period.

I thought about this option, this will require CPUs to be added to
whitelist too. If the maintainers wont hate it, I will go this route.