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

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Date:	Wed, 11 Nov 2015 08:12:23 -0500
From:	Austin S Hemmelgarn <ahferroin7@...il.com>
To:	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 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 :))



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