From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC PATCH 16/18] KVM: add kvm_arch_vcpu_prevent_run to prevent VM ENTER when NMI is received Date: Thu, 28 Jun 2012 19:48:59 +0300 Message-ID: <4FEC8AFB.8060606@redhat.com> References: <20120628060719.19298.43879.stgit@localhost.localdomain> <20120628060842.19298.14653.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, yrl.pp-manager.tt@hitachi.com, Marcelo Tosatti , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" To: Tomoki Sekiyama Return-path: In-Reply-To: <20120628060842.19298.14653.stgit@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 06/28/2012 09:08 AM, Tomoki Sekiyama wrote: > Since NMI can not be disabled around VM enter, there is a race between > receiving NMI to kick a guest and entering the guests on slave CPUs.If the > NMI is received just before entering VM, after the NMI handler is invoked, > it continues entering the guest and the effect of the NMI will be lost. > > This patch adds kvm_arch_vcpu_prevent_run(), which causes VM exit right > after VM enter. The NMI handler uses this to ensure the execution of the > guest is cancelled after NMI. > > > +/* > + * Make VMRESUME fail using preemption timer with timer value = 0. > + * On processors that doesn't support preemption timer, VMRESUME will fail > + * by internal error. > + */ > +static void vmx_prevent_run(struct kvm_vcpu *vcpu, int prevent) > +{ > + if (prevent) > + vmcs_set_bits(PIN_BASED_VM_EXEC_CONTROL, > + PIN_BASED_PREEMPTION_TIMER); > + else > + vmcs_clear_bits(PIN_BASED_VM_EXEC_CONTROL, > + PIN_BASED_PREEMPTION_TIMER); > +} This may interrupt another RMW sequence, which will then overwrite the control. So it needs to be called only if inside the entry sequence (otherwise can just set a KVM_REQ_IMMEDIATE_EXIT in vcpu->requests). -- error compiling committee.c: too many arguments to function