From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1906823-1518711308-2-9550326507751063084 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1518711308; b=AHgFW7h5VByiKS4TKQ3IT5T/VSVDtnszueO3g0x2fEjAzOa KmP/nMu7/Rkj9PHc3oEhKOiwU+ZNuysEwItIj4Pqr9XzJ5nv7smm3iBWzYJIUZBG y0JeoXvujdNk7iW+pqw8Kgc4o9gZpS0IpoSQ66efMhTsAfZdTd/FrPZ4TfM+Aq25 iTV6vXwYnggDgEYwgU3Rt0P2mTm71RC4t4ykXxuPtguV0Kea6Ll+RzwggN5SXBeW 48XmxE4HthJJIXQwDBE5WoRReBLej6XfDR8gV+VBWQ0cBvs1Ip2fZ56NKd3vlb3H U97pJ6zyjuJqx4hYPy5Uv+Uyl41aJKQZUA9G9jQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-type:sender :list-id; s=arctest; t=1518711308; bh=GtbiYsPAUwcL/0lRb2XDxhtbGG r+McaWjqTp3Tu/ICc=; b=YyekmFKsi0vNsro8msAdpJcm+HPs6bUrWKW0pvXKpO Vb2gPvvxb2kkWRrLwoqFJ26VePL2P42178OqFwV0zVEz0QQuHQOvWQ/+AlOvYkjD pc8+5bSaTzCB5/VPNC4ZI2AN5x0j7KvC07CRwP1tjbBqwxI61LQFCK+qKyWS0lE5 auc6bQT8qWbWmKvClIdJrthlyJauZvpoxDeJWTotRUor17XdmlQsKaQYu8NmlIuj xkEDaigXAZi5W/Qeg8VKZmCMud7PugSEeTRlzxrwH2jaGm1ytUHg1rerTXjSuTKA IguZW0T8e3K2KzCb1tuLQaVFrfHA6sIltY2vrW5OftPQ== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424281AbeBOPon (ORCPT ); Thu, 15 Feb 2018 10:44:43 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:34434 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423899AbeBOPom (ORCPT ); Thu, 15 Feb 2018 10:44:42 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paul Mackerras Subject: [PATCH 4.15 134/202] KVM: PPC: Book3S HV: Drop locks before reading guest memory Date: Thu, 15 Feb 2018 16:17:14 +0100 Message-Id: <20180215151720.160232830@linuxfoundation.org> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180215151712.768794354@linuxfoundation.org> References: <20180215151712.768794354@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul Mackerras commit 36ee41d161c67a6fcf696d4817a0da31f778938c upstream. Running with CONFIG_DEBUG_ATOMIC_SLEEP reveals that HV KVM tries to read guest memory, in order to emulate guest instructions, while preempt is disabled and a vcore lock is held. This occurs in kvmppc_handle_exit_hv(), called from post_guest_process(), when emulating guest doorbell instructions on POWER9 systems, and also when checking whether we have hit a hypervisor breakpoint. Reading guest memory can cause a page fault and thus cause the task to sleep, so we need to avoid reading guest memory while holding a spinlock or when preempt is disabled. To fix this, we move the preempt_enable() in kvmppc_run_core() to before the loop that calls post_guest_process() for each vcore that has just run, and we drop and re-take the vcore lock around the calls to kvmppc_emulate_debug_inst() and kvmppc_emulate_doorbell_instr(). Dropping the lock is safe with respect to the iteration over the runnable vcpus in post_guest_process(); for_each_runnable_thread is actually safe to use locklessly. It is possible for a vcpu to become runnable and add itself to the runnable_threads array (code near the beginning of kvmppc_run_vcpu()) and then get included in the iteration in post_guest_process despite the fact that it has not just run. This is benign because vcpu->arch.trap and vcpu->arch.ceded will be zero. Fixes: 579006944e0d ("KVM: PPC: Book3S HV: Virtualize doorbell facility on POWER9") Signed-off-by: Paul Mackerras Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kvm/book3s_hv.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1005,8 +1005,6 @@ static int kvmppc_emulate_doorbell_instr struct kvm *kvm = vcpu->kvm; struct kvm_vcpu *tvcpu; - if (!cpu_has_feature(CPU_FTR_ARCH_300)) - return EMULATE_FAIL; if (kvmppc_get_last_inst(vcpu, INST_GENERIC, &inst) != EMULATE_DONE) return RESUME_GUEST; if (get_op(inst) != 31) @@ -1056,6 +1054,7 @@ static int kvmppc_emulate_doorbell_instr return RESUME_GUEST; } +/* Called with vcpu->arch.vcore->lock held */ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu, struct task_struct *tsk) { @@ -1176,7 +1175,10 @@ static int kvmppc_handle_exit_hv(struct swab32(vcpu->arch.emul_inst) : vcpu->arch.emul_inst; if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) { + /* Need vcore unlocked to call kvmppc_get_last_inst */ + spin_unlock(&vcpu->arch.vcore->lock); r = kvmppc_emulate_debug_inst(run, vcpu); + spin_lock(&vcpu->arch.vcore->lock); } else { kvmppc_core_queue_program(vcpu, SRR1_PROGILL); r = RESUME_GUEST; @@ -1191,8 +1193,13 @@ static int kvmppc_handle_exit_hv(struct */ case BOOK3S_INTERRUPT_H_FAC_UNAVAIL: r = EMULATE_FAIL; - if ((vcpu->arch.hfscr >> 56) == FSCR_MSGP_LG) + if (((vcpu->arch.hfscr >> 56) == FSCR_MSGP_LG) && + cpu_has_feature(CPU_FTR_ARCH_300)) { + /* Need vcore unlocked to call kvmppc_get_last_inst */ + spin_unlock(&vcpu->arch.vcore->lock); r = kvmppc_emulate_doorbell_instr(vcpu); + spin_lock(&vcpu->arch.vcore->lock); + } if (r == EMULATE_FAIL) { kvmppc_core_queue_program(vcpu, SRR1_PROGILL); r = RESUME_GUEST; @@ -2934,13 +2941,14 @@ static noinline void kvmppc_run_core(str /* make sure updates to secondary vcpu structs are visible now */ smp_mb(); + preempt_enable(); + for (sub = 0; sub < core_info.n_subcores; ++sub) { pvc = core_info.vc[sub]; post_guest_process(pvc, pvc == vc); } spin_lock(&vc->lock); - preempt_enable(); out: vc->vcore_state = VCORE_INACTIVE;