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Bhat" Subject: [PATCH v6 29/46] kvm/vmx: Use get/put_online_cpus_atomic() to prevent CPU offline To: tglx@linutronix.de, peterz@infradead.org, tj@kernel.org, oleg@redhat.com, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org Date: Mon, 18 Feb 2013 18:12:26 +0530 Message-ID: <20130218124226.26245.11310.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130218123714.26245.61816.stgit@srivatsabhat.in.ibm.com> References: <20130218123714.26245.61816.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13021812-5564-0000-0000-000006A63525 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130218_074433_323118_0F4DBA21 X-CRM114-Status: GOOD ( 13.71 ) X-Spam-Score: -1.9 (-) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-1.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [122.248.162.4 listed in list.dnswl.org] 3.0 KHOP_BIG_TO_CC Sent to 10+ recipients instaed of Bcc or a list -0.7 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: linux-arch@vger.kernel.org, linux@arm.linux.org.uk, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, fweisbec@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, xiaoguangrong@linux.vnet.ibm.com, rjw@sisk.pl, sbw@mit.edu, wangyun@linux.vnet.ibm.com, srivatsa.bhat@linux.vnet.ibm.com, netdev@vger.kernel.org, vincent.guittot@linaro.org, walken@google.com, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Once stop_machine() is gone from the CPU offline path, we won't be able to depend on preempt_disable() or local_irq_disable() to prevent CPUs from going offline from under us. Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context (in vmx_vcpu_load() to prevent CPUs from going offline while clearing vmcs). Reported-by: Michael Wang Debugged-by: Xiao Guangrong Cc: Marcelo Tosatti Cc: Gleb Natapov Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: kvm@vger.kernel.org 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 9120ae1..2886ff0 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1557,10 +1557,14 @@ 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;