From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out1-smtp.messagingengine.com ([66.111.4.25]:35543 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751181AbdJCIyH (ORCPT ); Tue, 3 Oct 2017 04:54:07 -0400 Date: Tue, 3 Oct 2017 10:54:15 +0200 From: Greg KH To: Haozhong Zhang Cc: stable@vger.kernel.org, Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , "Ramamurthy, Venkatesh" , Dan Williams Subject: Re: [PATCH-for-4.13 2/2] KVM: VMX: remove WARN_ON_ONCE in kvm_vcpu_trigger_posted_interrupt Message-ID: <20171003085415.GE15659@kroah.com> References: <20170927032240.21406-1-haozhong.zhang@intel.com> <20170927032240.21406-3-haozhong.zhang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170927032240.21406-3-haozhong.zhang@intel.com> Sender: stable-owner@vger.kernel.org List-ID: On Wed, Sep 27, 2017 at 11:22:40AM +0800, Haozhong Zhang wrote: > commit 5753743fa5108b8f98bd61e40dc63f641b26c768 upstream. > > WARN_ON_ONCE(pi_test_sn(&vmx->pi_desc)) in kvm_vcpu_trigger_posted_interrupt() > intends to detect the violation of invariant that VT-d PI notification > event is not suppressed when vcpu is in the guest mode. Because the > two checks for the target vcpu mode and the target suppress field > cannot be performed atomically, the target vcpu mode may change in > between. If that does happen, WARN_ON_ONCE() here may raise false > alarms. > > As the previous patch fixed the real invariant breaker, remove this > WARN_ON_ONCE() to avoid false alarms, and document the allowed cases > instead. > > Signed-off-by: Haozhong Zhang > Reported-by: "Ramamurthy, Venkatesh" > Reported-by: Dan Williams > Reviewed-by: Paolo Bonzini > Fixes: 28b835d60fcc ("KVM: Update Posted-Interrupts Descriptor when vCPU is preempted") Also applied to 4.4 and 4.9-stable trees, thanks. greg k-h