linux-kernel - Re: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since race

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Date:	Wed, 02 Jul 2014 11:03:25 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	"Hu, Robert" <robert.hu@...el.com>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Gleb Natapov <gleb@...nel.org>
CC:	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since
 race

On 2014-07-02 09:20, Hu, Robert wrote:
>> -----Original Message-----
>> From: Wanpeng Li [mailto:wanpeng.li@...ux.intel.com]
>> Sent: Wednesday, July 2, 2014 2:54 PM
>> To: Paolo Bonzini; Jan Kiszka; Gleb Natapov
>> Cc: Hu, Robert; kvm@...r.kernel.org; linux-kernel@...r.kernel.org; Wanpeng Li
>> Subject: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since race
>>
>> This patch fix bug https://bugzilla.kernel.org/show_bug.cgi?id=72381
>>
>> If we didn't inject a still-pending event to L1 since nested_run_pending,
>> KVM_REQ_EVENT should be requested after the vmexit in order to inject the
>> event to L1. However, current log blindly request a KVM_REQ_EVENT even if
>> there is no still-pending event to L1 which blocked by nested_run_pending.
>> There is a race which lead to an interrupt will be injected to L2 which
>> belong to L1 if L0 send an interrupt to L1 during this window.
>>
>>                VCPU0                               another thread
>>
>> L1 intr not blocked on L2 first entry
>> vmx_vcpu_run req event
>> kvm check request req event
>> check_nested_events don't have any intr
>> not nested exit
>>                                             intr occur (8254, lapic timer
>> etc)
>> inject_pending_event now have intr
>> inject interrupt
>>
>> This patch fix this race by introduced a l1_events_blocked field in nested_vmx
>> which indicates there is still-pending event which blocked by
>> nested_run_pending,
>> and smart request a KVM_REQ_EVENT if there is a still-pending event which
>> blocked
>> by nested_run_pending.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
> Tested-by: Robert Hu<robert.hu@...el.com>

Do you happen to have a kvm-unit-test for this race? Or how did you
test? Just curious, and if there is a test, it would be good to
integrate it.

Jan

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