linux-kernel - Re: [patch V2 04/25] x86/apic: Make apic_pending_intr

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Message-ID: <f4b39e63-9587-176c-697a-e91f0af357de@citrix.com>
Date:   Fri, 5 Jul 2019 22:16:50 +0100
From:   Andrew Cooper <andrew.cooper3@...rix.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
CC:     LKML <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        Nadav Amit <namit@...are.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Feng Tang <feng.tang@...el.com>,
        "Andy Lutomirski" <luto@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>
Subject: Re: [patch V2 04/25] x86/apic: Make apic_pending_intr_clear() more
 robust

On 05/07/2019 21:49, Paolo Bonzini wrote:
> On 05/07/19 22:25, Thomas Gleixner wrote:
>> In practice, this makes Linux vulnerable to CVE-2011-1898 / XSA-3, which
>> I'm disappointed to see wasn't shared with other software vendors at the
>> time.
> Oh, that brings back memories.  At the time I was working on Xen, so I
> remember that CVE.  IIRC there was some mitigation but the fix was
> basically to print a very scary error message if you used VT-d without
> interrupt remapping.  Maybe force the user to add something on the Xen
> command line too?

It was before my time.  I have no public comment on how the other
aspects of it were handled.

>> Is there any serious usage of virtualization w/o interrupt remapping left
>> or have the machines which are not capable been retired already?
> I think they were already starting to disappear in 2011, as I don't
> remember much worry about customers that were using systems without it.

ISTR Nehalem/Westmere era systems were the first to support interrupt
remapping, but were totally crippled with errata to the point of needing
to turn a prerequisite feature (Queued Invalidation) off.  I believe
later systems have it working to a first approximation.

As to the original question, whether people should be using such systems
is a different question to whether they actually are.

~Andrew