From patchwork Tue Nov 5 07:42:43 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pingfan Liu X-Patchwork-Id: 288403 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from ozlabs.org (localhost [IPv6:::1]) by ozlabs.org (Postfix) with ESMTP id B41502C057B for ; Tue, 5 Nov 2013 18:43:15 +1100 (EST) Received: from mail-pa0-x22d.google.com (mail-pa0-x22d.google.com [IPv6:2607:f8b0:400e:c03::22d]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (not verified)) by ozlabs.org (Postfix) with ESMTPS id CEBE72C034E for ; Tue, 5 Nov 2013 18:42:25 +1100 (EST) Received: by mail-pa0-f45.google.com with SMTP id kp14so8202814pab.32 for ; Mon, 04 Nov 2013 23:42:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=4KxjBJN1F2f8J4sBTTVXd+1th2ou19NUeDTqZrp8S2U=; b=X097dEMa3mGzO/hBosNVCDS325pa2mxb/qeojX4jLvNZ/x47bhPu/dCxxPCDUmgaMU uB+qolw0NNJOLcuyTx8zDujvkXTs6GR0RSxECfjrwIzqq4EcwkmaQn0FvX1F55Inkwdo SphQBPgTaK8XIOWkVoIdkfJQbb+e39ABrMsKGD0Ia26zBGIr5t6XSwzQpYVLLxa6KFnw cuqnTAfAEQFTC64StSd5imj72F0Nslakv171I/Du9fdkhVk79skwKLF9KCF5xLT+Nw24 kB7kp2t1Kk+qgyYxAKgcSyNM+KkgXzCyQt3F386ZTiontwB9HhyRwwTaQOI4Npg7xjPv Fl2w== X-Received: by 10.67.3.34 with SMTP id bt2mr21919920pad.3.1383637343164; Mon, 04 Nov 2013 23:42:23 -0800 (PST) Received: from localhost ([202.108.130.138]) by mx.google.com with ESMTPSA id sd3sm32775810pbb.42.2013.11.04.23.42.21 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Mon, 04 Nov 2013 23:42:22 -0800 (PST) From: Liu Ping Fan To: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org Subject: [PATCH 2/3] powerpc/kvm: fix rare but potential deadlock scene Date: Tue, 5 Nov 2013 15:42:43 +0800 Message-Id: <1383637364-14691-2-git-send-email-pingfank@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1383637364-14691-1-git-send-email-pingfank@linux.vnet.ibm.com> References: <1383637364-14691-1-git-send-email-pingfank@linux.vnet.ibm.com> Cc: Paul Mackerras , Alexander Graf X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.16rc2 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Since kvmppc_hv_find_lock_hpte() is called from both virtmode and realmode, so it can trigger the deadlock. Suppose the following scene: Two physical cpuM, cpuN, two VM instances A, B, each VM has a group of vcpus. If on cpuM, vcpu_A_1 holds bitlock X (HPTE_V_HVLOCK), then is switched out, and on cpuN, vcpu_A_2 try to lock X in realmode, then cpuN will be caught in realmode for a long time. What makes things even worse if the following happens, On cpuM, bitlockX is hold, on cpuN, Y is hold. vcpu_B_2 try to lock Y on cpuM in realmode vcpu_A_2 try to lock X on cpuN in realmode Oops! deadlock happens Signed-off-by: Liu Ping Fan --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 043eec8..28160ac 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -474,8 +474,10 @@ static int kvmppc_mmu_book3s_64_hv_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, } /* Find the HPTE in the hash table */ + preempt_disable(); index = kvmppc_hv_find_lock_hpte(kvm, eaddr, slb_v, HPTE_V_VALID | HPTE_V_ABSENT); + preempt_enable(); if (index < 0) return -ENOENT; hptep = (unsigned long *)(kvm->arch.hpt_virt + (index << 4));