From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [RFC PATCH v4 8/9] kvm, vmx: Add atomic synchronization with CPU Hotplug Date: Tue, 11 Dec 2012 19:35:32 +0530 Message-ID: <20121211140528.23621.52490.stgit@srivatsabhat.in.ibm.com> References: <20121211140314.23621.64088.stgit@srivatsabhat.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121211140314.23621.64088.stgit@srivatsabhat.in.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: tglx@linutronix.de, peterz@infradead.org, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org, vincent.guittot@linaro.org, tj@kernel.org, oleg@redhat.com Cc: sbw@mit.edu, amit.kucheria@linaro.org, rostedt@goodmis.org, rjw@sisk.pl, srivatsa.bhat@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org preempt_disable() will no longer help prevent CPUs from going offline, once stop_machine() gets removed from the CPU offline path. So use get/put_online_cpus_atomic() in vmx_vcpu_load() to prevent CPUs from going offline while clearing vmcs. Reported-by: Michael Wang Debugged-by: Xiao Guangrong Signed-off-by: Srivatsa S. Bhat --- arch/x86/kvm/vmx.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index f858159..d8a4cf1 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1519,10 +1519,14 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) struct vcpu_vmx *vmx = to_vmx(vcpu); u64 phys_addr = __pa(per_cpu(vmxarea, cpu)); - if (!vmm_exclusive) + if (!vmm_exclusive) { kvm_cpu_vmxon(phys_addr); - else if (vmx->loaded_vmcs->cpu != cpu) + } else if (vmx->loaded_vmcs->cpu != cpu) { + /* Prevent any CPU from going offline */ + get_online_cpus_atomic(); loaded_vmcs_clear(vmx->loaded_vmcs); + put_online_cpus_atomic(); + } if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) { per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;