linux-kernel - Re: [PATCH] x86: kvm: reset the bootstrap processor when it gets an INIT

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Date:	Tue, 12 Mar 2013 10:25:35 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Paolo Bonzini <pbonzini@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"mtosatti@...hat.com" <mtosatti@...hat.com>
Subject: Re: [PATCH] x86: kvm: reset the bootstrap processor when it gets
 an INIT

On 2013-03-11 20:30, Gleb Natapov wrote:
> On Mon, Mar 11, 2013 at 08:01:30PM +0100, Jan Kiszka wrote:
>> On 2013-03-11 19:51, Gleb Natapov wrote:
>>>>> On Intel:
>>>>> CPU 1                          CPU 2 in a guest mode
>>>>> send INIT
>>>>> send SIPI
>>>>>                                 INIT vmexit
>>>>>                                 vmxoff
>>>>>                                 reset and start from SIPI vector
>>>>
>>>> Is SIPI sticky as well, even if the CPU is not in the wait-for-SIPI
>>>> state (but runnable and in vmxon) while receiving it?
>>>>
>>> That what they seams to be saying:
>>>  However, an INIT and SIPI interrupts sent to a CPU during time when
>>>  it is in a VMX mode are remembered and delivered, perhaps hours later,
>>>  when the CPU exits the VMX mode
>>>
>>> Otherwise their exploit will not work.
>>
>> Very weird, specifically as SIPI is not just a binary event but carries
>> payload. Will another SIPI event overwrite the previously "saved"
>> vector? We are deep into an underspecified area...
> My guess is that VMX INIT blocking is done by the same mechanism as
> INIT blocking during SMM. Obviously after exit from SMM pending
> INIT/SIPI have to be processed.

I think this should be further examined via a test case that can run on
real HW. Is kvm-unit-test ready for this? Then we "just" need to
implement what you were already asking for: minimalistic nVMX tests...

Jan

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