From patchwork Wed Jan 11 18:06:51 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13097077 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67669C46467 for ; Wed, 11 Jan 2023 18:07:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234237AbjAKSHI (ORCPT ); Wed, 11 Jan 2023 13:07:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234623AbjAKSG7 (ORCPT ); Wed, 11 Jan 2023 13:06:59 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1819218B20 for ; Wed, 11 Jan 2023 10:06:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=M7OewXuuc2RwiC+Z+c7QuSOrIFr3cHINnhaYsxajvJ0=; b=UvcDXRfrcQhpLdPgWH54u/HBfv /6cbWRBQbz0rkgEhQO9J4YUZ+OZ77LRgLFgcJubWm7GvJo3DNG147Hn+5VV0CX5Bpnf+7FHjskY+o OUzZgOpShv3Gh0LakFITjF9LQY7PHaJHi+H5iZux4Y+6Lx99KPFw7c9eyX3SzLvrICHKrUikIrpLz SUJ2M24+kR3TSQ9GRxvZAlBxrcfxobdRaA8ADoHoRiy1B3TcsHCWSo8/s8UfCQuvnayCu5SrqTm86 naSf64NSYsAgt2Hnh8B+NWM/aXadxCvNzMsEfywtpz3CGgIj0RJTyxbkKLnqqCuK3aDue2bisGxLG EQi4+mqw==; Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pFfUp-003lME-1t; Wed, 11 Jan 2023 18:06:43 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pFfUx-0003kX-7X; Wed, 11 Jan 2023 18:06:51 +0000 From: David Woodhouse To: kvm@vger.kernel.org Cc: Peter Zijlstra , Paolo Bonzini , paul , Sean Christopherson , Michal Luczaj Subject: [PATCH v2 4/4] KVM: x86/xen: Avoid deadlock by adding kvm->arch.xen.xen_lock leaf node lock Date: Wed, 11 Jan 2023 18:06:51 +0000 Message-Id: <20230111180651.14394-4-dwmw2@infradead.org> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20230111180651.14394-1-dwmw2@infradead.org> References: <20230111180651.14394-1-dwmw2@infradead.org> MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse In commit 14243b387137a ("KVM: x86/xen: Add KVM_IRQ_ROUTING_XEN_EVTCHN and event channel delivery") the clever version of me left some helpful notes for those who would come after him: /* * For the irqfd workqueue, using the main kvm->lock mutex is * fine since this function is invoked from kvm_set_irq() with * no other lock held, no srcu. In future if it will be called * directly from a vCPU thread (e.g. on hypercall for an IPI) * then it may need to switch to using a leaf-node mutex for * serializing the shared_info mapping. */ mutex_lock(&kvm->lock); In commit 2fd6df2f2b47 ("KVM: x86/xen: intercept EVTCHNOP_send from guests") the other version of me ran straight past that comment without reading it, and introduced a potential deadlock by taking vcpu->mutex and kvm->lock in the wrong order. Solve this as originally suggested, by adding a leaf-node lock in the Xen state rather than using kvm->lock for it. Fixes: 2fd6df2f2b47 ("KVM: x86/xen: intercept EVTCHNOP_send from guests") Signed-off-by: David Woodhouse --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/xen.c | 65 +++++++++++++++------------------ 2 files changed, 30 insertions(+), 36 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 2f5bf581d00a..4ef0143fa682 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1115,6 +1115,7 @@ struct msr_bitmap_range { /* Xen emulation context */ struct kvm_xen { + struct mutex xen_lock; u32 xen_version; bool long_mode; bool runstate_update_flag; diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 809b82bdb9c3..8bebc41f8f9e 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -608,26 +608,26 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) if (!IS_ENABLED(CONFIG_64BIT) && data->u.long_mode) { r = -EINVAL; } else { - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); kvm->arch.xen.long_mode = !!data->u.long_mode; - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); r = 0; } break; case KVM_XEN_ATTR_TYPE_SHARED_INFO: - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); r = kvm_xen_shared_info_init(kvm, data->u.shared_info.gfn); - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); break; case KVM_XEN_ATTR_TYPE_UPCALL_VECTOR: if (data->u.vector && data->u.vector < 0x10) r = -EINVAL; else { - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); kvm->arch.xen.upcall_vector = data->u.vector; - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); r = 0; } break; @@ -637,9 +637,9 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) break; case KVM_XEN_ATTR_TYPE_XEN_VERSION: - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); kvm->arch.xen.xen_version = data->u.xen_version; - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); r = 0; break; @@ -648,9 +648,9 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) r = -EOPNOTSUPP; break; } - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); kvm->arch.xen.runstate_update_flag = !!data->u.runstate_update_flag; - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); r = 0; break; @@ -665,7 +665,7 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) { int r = -ENOENT; - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); switch (data->type) { case KVM_XEN_ATTR_TYPE_LONG_MODE: @@ -704,7 +704,7 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) break; } - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); return r; } @@ -712,7 +712,7 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) { int idx, r = -ENOENT; - mutex_lock(&vcpu->kvm->lock); + mutex_lock(&vcpu->kvm->arch.xen.xen_lock); idx = srcu_read_lock(&vcpu->kvm->srcu); switch (data->type) { @@ -940,7 +940,7 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) } srcu_read_unlock(&vcpu->kvm->srcu, idx); - mutex_unlock(&vcpu->kvm->lock); + mutex_unlock(&vcpu->kvm->arch.xen.xen_lock); return r; } @@ -948,7 +948,7 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) { int r = -ENOENT; - mutex_lock(&vcpu->kvm->lock); + mutex_lock(&vcpu->kvm->arch.xen.xen_lock); switch (data->type) { case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO: @@ -1031,7 +1031,7 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) break; } - mutex_unlock(&vcpu->kvm->lock); + mutex_unlock(&vcpu->kvm->arch.xen.xen_lock); return r; } @@ -1124,7 +1124,7 @@ int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc) xhc->blob_size_32 || xhc->blob_size_64)) return -EINVAL; - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); if (xhc->msr && !kvm->arch.xen_hvm_config.msr) static_branch_inc(&kvm_xen_enabled.key); @@ -1133,7 +1133,7 @@ int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc) memcpy(&kvm->arch.xen_hvm_config, xhc, sizeof(*xhc)); - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); return 0; } @@ -1676,15 +1676,7 @@ static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm) mm_borrowed = true; } - /* - * For the irqfd workqueue, using the main kvm->lock mutex is - * fine since this function is invoked from kvm_set_irq() with - * no other lock held, no srcu. In future if it will be called - * directly from a vCPU thread (e.g. on hypercall for an IPI) - * then it may need to switch to using a leaf-node mutex for - * serializing the shared_info mapping. - */ - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); /* * It is theoretically possible for the page to be unmapped @@ -1713,7 +1705,7 @@ static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm) srcu_read_unlock(&kvm->srcu, idx); } while(!rc); - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); if (mm_borrowed) kthread_unuse_mm(kvm->mm); @@ -1829,7 +1821,7 @@ static int kvm_xen_eventfd_update(struct kvm *kvm, int ret; /* Protect writes to evtchnfd as well as the idr lookup. */ - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); evtchnfd = idr_find(&kvm->arch.xen.evtchn_ports, port); ret = -ENOENT; @@ -1860,7 +1852,7 @@ static int kvm_xen_eventfd_update(struct kvm *kvm, } ret = 0; out_unlock: - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); return ret; } @@ -1923,10 +1915,10 @@ static int kvm_xen_eventfd_assign(struct kvm *kvm, evtchnfd->deliver.port.priority = data->u.evtchn.deliver.port.priority; } - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); ret = idr_alloc(&kvm->arch.xen.evtchn_ports, evtchnfd, port, port + 1, GFP_KERNEL); - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); if (ret >= 0) return 0; @@ -1944,9 +1936,9 @@ static int kvm_xen_eventfd_deassign(struct kvm *kvm, u32 port) { struct evtchnfd *evtchnfd; - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); evtchnfd = idr_remove(&kvm->arch.xen.evtchn_ports, port); - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); if (!evtchnfd) return -ENOENT; @@ -1963,7 +1955,7 @@ static int kvm_xen_eventfd_reset(struct kvm *kvm) struct evtchnfd *evtchnfd; int i; - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.xen.xen_lock); idr_for_each_entry(&kvm->arch.xen.evtchn_ports, evtchnfd, i) { idr_remove(&kvm->arch.xen.evtchn_ports, evtchnfd->send_port); synchronize_srcu(&kvm->srcu); @@ -1971,7 +1963,7 @@ static int kvm_xen_eventfd_reset(struct kvm *kvm) eventfd_ctx_put(evtchnfd->deliver.eventfd.ctx); kfree(evtchnfd); } - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.xen.xen_lock); return 0; } @@ -2063,6 +2055,7 @@ void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu) void kvm_xen_init_vm(struct kvm *kvm) { + mutex_init(&kvm->arch.xen.xen_lock); idr_init(&kvm->arch.xen.evtchn_ports); kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm, NULL, KVM_HOST_USES_PFN); }