linux-kernel - Re: [PATCH 0/3] Infinite loops in microcode while running guests

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Date:	Thu, 12 Nov 2015 15:37:25 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>,
	Austin S Hemmelgarn <ahferroin7@...il.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:	digitaleric@...gle.com
Subject: Re: [PATCH 0/3] Infinite loops in microcode while running guests



On 12/11/2015 15:08, Jan Kiszka wrote:
> On 2015-11-11 14:12, Austin S Hemmelgarn wrote:
>> On 2015-11-11 08:07, Paolo Bonzini wrote:
>>>
>>>
>>> On 11/11/2015 13:47, Austin S Hemmelgarn wrote:
>>>>>
>>>> I just finished running a couple of tests in a KVM instance running
>>>> nested on a Xen HVM instance, and found no issues, so for the set as a
>>>> whole:
>>>>
>>>> Tested-by: Austin S. Hemmelgarn <ahferroin7@...il.com>
>>>>
>>>> Now to hope the equivalent fix for Xen gets into the Gentoo repositories
>>>> soon, as the issue propagates down through nested virtualization and
>>>> ties up the CPU regardless (and in turn triggers the watchdog).
>>>
>>> Note that nested guests should _not_ lock up the outer (L0) hypervisor
>>> if the outer hypervisor has the fix.  At least this is the case for KVM:
>>> a fixed outer KVM can protect any vulnerable nested (L1) hypervisor from
>>> malicious nested guests.  A vulnerable outer KVM is also protected if
>>> the nested hypervisor has the workaround.
>>>
>> I already knew this, I just hadn't remembered that I hadn't updated Xen
>> since before the XSA and patch for this had been posted (and it took me
>> a while to remember this when I accidentally panicked Xen :))
> 
> As I'm lazy, both to search and to write something myself: is there
> already a test case for the issue(s) circling around?

To everybody: keep reproducers offlist, please.

Paolo
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