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

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Message-ID: <20220730023151.kogebjrhsvhitklj@desk>
Date:   Fri, 29 Jul 2022 19:31:51 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     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,
        tony.luck@...el.com, 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 Sat, Jul 30, 2022 at 12:02:34AM +0200, Borislav Petkov wrote:
> On Fri, Jul 29, 2022 at 02:46:27PM -0700, 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				?
> 
> Not affected current CPUs should be arch_cap_mmio_immune() == true, no?

That would be true in most cases, with some exceptions like systems
that did not update the microcode.