From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DB451C282DE for ; Thu, 23 May 2019 06:36:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A0BFC21019 for ; Thu, 23 May 2019 06:36:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ozlabs.org header.i=@ozlabs.org header.b="pnayADD3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727466AbfEWGgq (ORCPT ); Thu, 23 May 2019 02:36:46 -0400 Received: from ozlabs.org ([203.11.71.1]:34359 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726385AbfEWGgp (ORCPT ); Thu, 23 May 2019 02:36:45 -0400 Received: by ozlabs.org (Postfix, from userid 1003) id 458ft353Lrz9sBV; Thu, 23 May 2019 16:36:43 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ozlabs.org; s=201707; t=1558593403; bh=XqYcC2hfPVNyLaizCQlvjY5iInJ3OLoLBVpPVN8v8LU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pnayADD3fDzj8vJX/tLcCYRdJwDw6tWApdyWE5oEFWXOPxNJxSuWp5d+ty16mEAuo Mw4B1rMAjWXRxUL+EMVQDivCDRpxGl6Wsrh84MnKGJ6KDYJ11z364cyiKURxPTVF6z Ddwn7xqP0fIrzv0gVM3EHjstnWfbInkoF48YeEPrLXIlWyKDnyHULm32iVd3WuNTtY WcOnwBsIiTTFiL98nCsnYCzxTxOJWUNleGfBl4AMFb7j1KAPJsXh4m+bPTQgb+cq6x ZBaZZI2uNSB877cKB7VnqUMFTudqsczK+guPMRCW16efIlzqCEJP97qYJbyuUQkoTL OMexRWIStWG9Q== Date: Thu, 23 May 2019 16:36:32 +1000 From: Paul Mackerras To: kvm@vger.kernel.org Cc: kvm-ppc@vger.kernel.org, =?iso-8859-1?Q?C=E9dric?= Le Goater Subject: [PATCH 4/4] KVM: PPC: Book3S HV: Don't take kvm->lock around kvm_for_each_vcpu Message-ID: <20190523063632.GF19655@blackberry> References: <20190523063424.GB19655@blackberry> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190523063424.GB19655@blackberry> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Currently the HV KVM code takes the kvm->lock around calls to kvm_for_each_vcpu() and kvm_get_vcpu_by_id() (which can call kvm_for_each_vcpu() internally). However, that leads to a lock order inversion problem, because these are called in contexts where the vcpu mutex is held, but the vcpu mutexes nest within kvm->lock according to Documentation/virtual/kvm/locking.txt. Hence there is a possibility of deadlock. To fix this, we simply don't take the kvm->lock mutex around these calls. This is safe because the implementations of kvm_for_each_vcpu() and kvm_get_vcpu_by_id() have been designed to be able to be called locklessly. Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s_hv.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index b1c0a9b..27054d3 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -446,12 +446,7 @@ static void kvmppc_dump_regs(struct kvm_vcpu *vcpu) static struct kvm_vcpu *kvmppc_find_vcpu(struct kvm *kvm, int id) { - struct kvm_vcpu *ret; - - mutex_lock(&kvm->lock); - ret = kvm_get_vcpu_by_id(kvm, id); - mutex_unlock(&kvm->lock); - return ret; + return kvm_get_vcpu_by_id(kvm, id); } static void init_vpa(struct kvm_vcpu *vcpu, struct lppaca *vpa) @@ -1583,7 +1578,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr, struct kvmppc_vcore *vc = vcpu->arch.vcore; u64 mask; - mutex_lock(&kvm->lock); spin_lock(&vc->lock); /* * If ILE (interrupt little-endian) has changed, update the @@ -1623,7 +1617,6 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr, mask &= 0xFFFFFFFF; vc->lpcr = (vc->lpcr & ~mask) | (new_lpcr & mask); spin_unlock(&vc->lock); - mutex_unlock(&kvm->lock); } static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id, -- 2.7.4