From patchwork Tue Jan 18 16:05:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 533511 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 861ACC433F5 for ; Tue, 18 Jan 2022 16:10:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346509AbiARQKR (ORCPT ); Tue, 18 Jan 2022 11:10:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51716 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243318AbiARQJV (ORCPT ); Tue, 18 Jan 2022 11:09:21 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9997BC06173F; Tue, 18 Jan 2022 08:09:20 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id EB2E4CE1A3E; Tue, 18 Jan 2022 16:09:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF611C00446; Tue, 18 Jan 2022 16:09:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1642522157; bh=WHbb0OXW8TtFj+QNFHxl7WaQnbFj5FU03ZDyBJMfPKI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nPiGQAGydvKJ8VQGn0x5SZO9WA4vHMB9qBaCpCXjS+V0b0w1xzo8Xus39Fpko0g+f iGtWZAVkoQh5bZTQ7UapOlK/uN/11PoJi8fcNAQvoeu3lFs5iAUniTf7Fih8w6RqME ngHivy4KvW/5kUaAA/sB73ee+ZJmQdGfkjtIDdWI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Hildenbrand , Eric Farman , Christian Borntraeger Subject: [PATCH 5.15 10/28] KVM: s390: Clarify SIGP orders versus STOP/RESTART Date: Tue, 18 Jan 2022 17:05:56 +0100 Message-Id: <20220118160452.224062485@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220118160451.879092022@linuxfoundation.org> References: <20220118160451.879092022@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric Farman commit 812de04661c4daa7ac385c0dfd62594540538034 upstream. With KVM_CAP_S390_USER_SIGP, there are only five Signal Processor orders (CONDITIONAL EMERGENCY SIGNAL, EMERGENCY SIGNAL, EXTERNAL CALL, SENSE, and SENSE RUNNING STATUS) which are intended for frequent use and thus are processed in-kernel. The remainder are sent to userspace with the KVM_CAP_S390_USER_SIGP capability. Of those, three orders (RESTART, STOP, and STOP AND STORE STATUS) have the potential to inject work back into the kernel, and thus are asynchronous. Let's look for those pending IRQs when processing one of the in-kernel SIGP orders, and return BUSY (CC2) if one is in process. This is in agreement with the Principles of Operation, which states that only one order can be "active" on a CPU at a time. Cc: stable@vger.kernel.org Suggested-by: David Hildenbrand Signed-off-by: Eric Farman Reviewed-by: Christian Borntraeger Acked-by: David Hildenbrand Link: https://lore.kernel.org/r/20211213210550.856213-2-farman@linux.ibm.com [borntraeger@linux.ibm.com: add stable tag] Signed-off-by: Christian Borntraeger Signed-off-by: Greg Kroah-Hartman --- arch/s390/kvm/interrupt.c | 7 +++++++ arch/s390/kvm/kvm-s390.c | 9 +++++++-- arch/s390/kvm/kvm-s390.h | 1 + arch/s390/kvm/sigp.c | 28 ++++++++++++++++++++++++++++ 4 files changed, 43 insertions(+), 2 deletions(-) --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -2115,6 +2115,13 @@ int kvm_s390_is_stop_irq_pending(struct return test_bit(IRQ_PEND_SIGP_STOP, &li->pending_irqs); } +int kvm_s390_is_restart_irq_pending(struct kvm_vcpu *vcpu) +{ + struct kvm_s390_local_interrupt *li = &vcpu->arch.local_int; + + return test_bit(IRQ_PEND_RESTART, &li->pending_irqs); +} + void kvm_s390_clear_stop_irq(struct kvm_vcpu *vcpu) { struct kvm_s390_local_interrupt *li = &vcpu->arch.local_int; --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -4642,10 +4642,15 @@ int kvm_s390_vcpu_stop(struct kvm_vcpu * } } - /* SIGP STOP and SIGP STOP AND STORE STATUS has been fully processed */ + /* + * Set the VCPU to STOPPED and THEN clear the interrupt flag, + * now that the SIGP STOP and SIGP STOP AND STORE STATUS orders + * have been fully processed. This will ensure that the VCPU + * is kept BUSY if another VCPU is inquiring with SIGP SENSE. + */ + kvm_s390_set_cpuflags(vcpu, CPUSTAT_STOPPED); kvm_s390_clear_stop_irq(vcpu); - kvm_s390_set_cpuflags(vcpu, CPUSTAT_STOPPED); __disable_ibs_on_vcpu(vcpu); for (i = 0; i < online_vcpus; i++) { --- a/arch/s390/kvm/kvm-s390.h +++ b/arch/s390/kvm/kvm-s390.h @@ -418,6 +418,7 @@ void kvm_s390_destroy_adapters(struct kv int kvm_s390_ext_call_pending(struct kvm_vcpu *vcpu); extern struct kvm_device_ops kvm_flic_ops; int kvm_s390_is_stop_irq_pending(struct kvm_vcpu *vcpu); +int kvm_s390_is_restart_irq_pending(struct kvm_vcpu *vcpu); void kvm_s390_clear_stop_irq(struct kvm_vcpu *vcpu); int kvm_s390_set_irq_state(struct kvm_vcpu *vcpu, void __user *buf, int len); --- a/arch/s390/kvm/sigp.c +++ b/arch/s390/kvm/sigp.c @@ -288,6 +288,34 @@ static int handle_sigp_dst(struct kvm_vc if (!dst_vcpu) return SIGP_CC_NOT_OPERATIONAL; + /* + * SIGP RESTART, SIGP STOP, and SIGP STOP AND STORE STATUS orders + * are processed asynchronously. Until the affected VCPU finishes + * its work and calls back into KVM to clear the (RESTART or STOP) + * interrupt, we need to return any new non-reset orders "busy". + * + * This is important because a single VCPU could issue: + * 1) SIGP STOP $DESTINATION + * 2) SIGP SENSE $DESTINATION + * + * If the SIGP SENSE would not be rejected as "busy", it could + * return an incorrect answer as to whether the VCPU is STOPPED + * or OPERATING. + */ + if (order_code != SIGP_INITIAL_CPU_RESET && + order_code != SIGP_CPU_RESET) { + /* + * Lockless check. Both SIGP STOP and SIGP (RE)START + * properly synchronize everything while processing + * their orders, while the guest cannot observe a + * difference when issuing other orders from two + * different VCPUs. + */ + if (kvm_s390_is_stop_irq_pending(dst_vcpu) || + kvm_s390_is_restart_irq_pending(dst_vcpu)) + return SIGP_CC_BUSY; + } + switch (order_code) { case SIGP_SENSE: vcpu->stat.instruction_sigp_sense++;