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Date:   Fri, 29 Jul 2022 10:45:21 -0700
From:   'Pawan Gupta' <pawan.kumar.gupta@linux.intel.com>
To:     David Laight <David.Laight@aculab.com>
Cc:     Borislav Petkov <bp@alien8.de>, Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "tony.luck@intel.com" <tony.luck@intel.com>,
        "antonio.gomez.iglesias@linux.intel.com" 
        <antonio.gomez.iglesias@linux.intel.com>,
        Daniel Sneddon <daniel.sneddon@linux.intel.com>,
        "andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
        Josh Poimboeuf <jpoimboe@kernel.org>
Subject: Re: [RESEND RFC PATCH] x86/bugs: Add "unknown" reporting for MMIO
 Stale Data
Message-ID: <20220729174521.kvbudqlpsoyvxzrv@desk>
References: <a932c154772f2121794a5f2eded1a11013114711.1657846269.git.pawan.kumar.gupta@linux.intel.com>
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On Fri, Jul 29, 2022 at 10:40:20AM +0000, David Laight wrote:
> From: Pawan Gupta
> > Sent: 29 July 2022 03:29
> > 
> > On Thu, Jul 28, 2022 at 02:00:13PM +0200, Borislav Petkov wrote:
> > > On Thu, Jul 14, 2022 at 06:30:18PM -0700, Pawan Gupta wrote:
> > > > Older CPUs beyond its Servicing period are not listed in the affected
> > > > processor list for MMIO Stale Data vulnerabilities. These CPUs currently
> > > > report "Not affected" in sysfs, which may not be correct.
> 
> I looked this up....
> 
> The mitigations seem to rely on unprivileged code not being able
> to do MMIO accesses.
> That isn't true, device drivers can mmap PCIe addresses directly
> into user program address space.
> While unlikely, there is no reason this can't be supported for
> non-root processes.

Agree. Would it be fair to assume that processes that get direct
hardware access are trusted?