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

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Message-ID: <56449D4B.8050500@siemens.com>
Date:	Thu, 12 Nov 2015 15:08:11 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>,
	Paolo Bonzini <pbonzini@...hat.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 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?

Thanks,
Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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