From patchwork Thu Jan 12 09:07:16 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Mackerras X-Patchwork-Id: 9512417 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 9549A60476 for ; Thu, 12 Jan 2017 09:08:04 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 88081285EB for ; Thu, 12 Jan 2017 09:08:04 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7CF1C286A7; Thu, 12 Jan 2017 09:08:04 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 249A7285EB for ; Thu, 12 Jan 2017 09:08:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751166AbdALJHp (ORCPT ); Thu, 12 Jan 2017 04:07:45 -0500 Received: from ozlabs.org ([103.22.144.67]:41157 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750998AbdALJHn (ORCPT ); Thu, 12 Jan 2017 04:07:43 -0500 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPSA id 3tzfzc6Nvzz9t2g; Thu, 12 Jan 2017 20:07:40 +1100 (AEDT) From: Paul Mackerras To: linuxppc-dev@ozlabs.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org Subject: [PATCH 08/18] KVM: PPC: Book3S HV: Don't try to signal cpu -1 Date: Thu, 12 Jan 2017 20:07:16 +1100 Message-Id: <1484212046-29591-9-git-send-email-paulus@ozlabs.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1484212046-29591-1-git-send-email-paulus@ozlabs.org> References: <1484212046-29591-1-git-send-email-paulus@ozlabs.org> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If the target vcpu for kvmppc_fast_vcpu_kick_hv() is not running on any CPU, then we will have vcpu->arch.thread_cpu == -1, and as it happens, kvmppc_fast_vcpu_kick_hv will call kvmppc_ipi_thread with -1 as the cpu argument. Although this is not meaningful, in the past, before commit 1704a81ccebc ("KVM: PPC: Book3S HV: Use msgsnd for IPIs to other cores on POWER9", 2016-11-18), it was harmless because CPU -1 is not in the same core as any real CPU thread. On a POWER9, however, we don't do the "same core" check, so we were trying to do a msgsnd to thread -1, which is invalid. To avoid this, we add a check to see that vcpu->arch.thread_cpu is >= 0 before calling kvmppc_ipi_thread() with it. Since vcpu->arch.thread_vcpu can change asynchronously, we use READ_ONCE to ensure that the value we check is the same value that we use as the argument to kvmppc_ipi_thread(). Fixes: 1704a81ccebc ("KVM: PPC: Book3S HV: Use msgsnd for IPIs to other cores on POWER9") Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s_hv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index ec34e39..8d9cc07 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -182,7 +182,8 @@ static void kvmppc_fast_vcpu_kick_hv(struct kvm_vcpu *vcpu) ++vcpu->stat.halt_wakeup; } - if (kvmppc_ipi_thread(vcpu->arch.thread_cpu)) + cpu = READ_ONCE(vcpu->arch.thread_cpu); + if (cpu >= 0 && kvmppc_ipi_thread(cpu)) return; /* CPU points to the first thread of the core */