From patchwork Tue Nov 19 06:12:47 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pingfan Liu X-Patchwork-Id: 292286 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 52F512C042F for ; Tue, 19 Nov 2013 17:12:35 +1100 (EST) Received: from mail-ob0-x236.google.com (mail-ob0-x236.google.com [IPv6:2607:f8b0:4003:c01::236]) (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 2A6092C00B6 for ; Tue, 19 Nov 2013 17:12:07 +1100 (EST) Received: by mail-ob0-f182.google.com with SMTP id wo20so3478791obc.13 for ; Mon, 18 Nov 2013 22:12:03 -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; bh=IN1mORTM7PlLdPHingg7zAP0McxyTJlxGrAsksN257U=; b=fyfbz6kqwlCsAwc2RMVO1+/lDI4z7OvJVPmhFgm9Gc4TXiAl6XTN/nEGzYi7k4Txte z1PQmawdnhSpcU90KgHPJyo/wVnQtGRgHh0UOODU344hEdF6Lp4SryhFBwtEm3cpZ3W9 Yq5k7TET6KQgxfW08x2lpI9iC0KYDGILtEOx29f1s+V8sZgXldHERnb8UAzYVzsWslkc WR7mpNgp/pgHjpprfVSJNNLGjlD7ONS0Ol4jeQIb2pHEpabtbcCMSt9epR3SNK6LHA6h cJQ/m2PuiHpANmj+K0G7P+GBYYn+SyAHwkLTi0TkDgToYNWk2WB6A4XdEpxGRo5GpDSb 3/aA== X-Received: by 10.60.149.169 with SMTP id ub9mr6375139oeb.39.1384841523202; Mon, 18 Nov 2013 22:12:03 -0800 (PST) Received: from localhost ([202.108.130.138]) by mx.google.com with ESMTPSA id ii8sm27743914obb.11.2013.11.18.22.12.01 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Mon, 18 Nov 2013 22:12:02 -0800 (PST) From: Liu Ping Fan To: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org Subject: [PATCH RESEND v4] powerpc: kvm: fix rare but potential deadlock scene Date: Tue, 19 Nov 2013 14:12:47 +0800 Message-Id: <1384841568-20986-1-git-send-email-pingfank@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.4 Cc: kvm@vger.kernel.org, Gleb Natapov , Alexander Graf , Paul Mackerras , Paolo Bonzini 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 | 6 +++++- arch/powerpc/kvm/book3s_hv_rm_mmu.c | 4 ++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 842f081..abf81fe 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -473,11 +473,14 @@ static int kvmppc_mmu_book3s_64_hv_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, slb_v = vcpu->kvm->arch.vrma_slb_v; } + preempt_disable(); /* Find the HPTE in the hash table */ index = kvmppc_hv_find_lock_hpte(kvm, eaddr, slb_v, HPTE_V_VALID | HPTE_V_ABSENT); - if (index < 0) + if (index < 0) { + preempt_enable(); return -ENOENT; + } hptep = (unsigned long *)(kvm->arch.hpt_virt + (index << 4)); v = hptep[0] & ~HPTE_V_HVLOCK; gr = kvm->arch.revmap[index].guest_rpte; @@ -485,6 +488,7 @@ static int kvmppc_mmu_book3s_64_hv_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, /* Unlock the HPTE */ asm volatile("lwsync" : : : "memory"); hptep[0] = v; + preempt_enable(); gpte->eaddr = eaddr; gpte->vpage = ((v & HPTE_V_AVPN) << 4) | ((eaddr >> 12) & 0xfff); diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c index 9c51544..ea17b30 100644 --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c @@ -749,6 +749,10 @@ static int slb_base_page_shift[4] = { 20, /* 1M, unsupported */ }; +/* When called from virtmode, this func should be protected by + * preempt_disable(), otherwise, the holding of HPTE_V_HVLOCK + * can trigger deadlock issue. + */ long kvmppc_hv_find_lock_hpte(struct kvm *kvm, gva_t eaddr, unsigned long slb_v, unsigned long valid) {