From patchwork Wed Sep 21 00:31:59 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12982862 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 E78A5C6FA8E for ; Wed, 21 Sep 2022 00:33:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231489AbiIUAdp (ORCPT ); Tue, 20 Sep 2022 20:33:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231320AbiIUAdN (ORCPT ); Tue, 20 Sep 2022 20:33:13 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 41102796B7 for ; Tue, 20 Sep 2022 17:33:05 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-349f88710b2so38120927b3.20 for ; Tue, 20 Sep 2022 17:33:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date; bh=6n3oC51LepjybeCO/G1gnLj/7i8/kZTfCzCfh49ZsFY=; b=W1Ft16I2z4KyotR0zf9JcaxskVjiFIoTSvcCvM9GzqpfMZjOnkUbTlyR/YK2GifRmv QrwJq8VMURYEAE2WuDaeBV1lpmfmiUr9qttHXPB25xmfj0zo/Rm8dS6hBczWKfely1To iBZYJPxQgEmeTx4V8oSgxXgoc7fmc8jL0B2eJu/Yc6c7NQPqonrY7m5HwsjgveG5t8/q DMeMlr+fihRcdrCqNFWVENW4RNE2K4oabECK0hGgUMWhs07ZJGDjNFB5aD/IHo4M7B6i xV1aDtVsD/LclbxQq81QXFA9WSGbWt0X054O++Zklv0EWWKP7bGtdKwjb1syoi10fSBt trFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date; bh=6n3oC51LepjybeCO/G1gnLj/7i8/kZTfCzCfh49ZsFY=; b=WGIxYvs23No09tnC+eobLyf7jfCKg0OBVFRHRH7Y6kHReuyCQcFfRCaY5OJuxQ9i/v HZIGfMHFLXggtQf+pr1K9fe7eoGIcp34SCCMVZxaAmcqlpbkTRvnLq0ui+z/rdOQQbhm ooDYtztDyRxIkp5xGmq8up+4Naw2MKDLB6ZpLxsG0yhegotzY+lnDPzPfgbBF9zOQO2V alAGEdTRiIg11rC4QnQphKoW0XQUx5vDNBO6e3fe4DuhTM8Vkcq/p6KwZ/IAbPZhUdCD RYSQrOY8cRnh6WQSmMOBbG+p+xncKbf9vWfS/Z+kSE5Pcb8O/75UcyHf4D7G9a6x5UTU 8p+g== X-Gm-Message-State: ACrzQf3nmSY53FzrvOxZMvY3sCEDmVoa5ypwkCa0VWNpl5g4H1OpVb0d ss156ypH0fmxWjU8etL0A/oyfvyQQZU= X-Google-Smtp-Source: AMsMyM6ajbNthck8O3WF1o+1c/8Kt+/LZ69NQ6nvF17LZv5xSYaJvw/YRsOuqwhN87Jz4vl4Gma5UjnRyp0= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:c04f:0:b0:6ae:96ac:ac2d with SMTP id c76-20020a25c04f000000b006ae96acac2dmr21142783ybf.227.1663720384571; Tue, 20 Sep 2022 17:33:04 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 21 Sep 2022 00:31:59 +0000 In-Reply-To: <20220921003201.1441511-1-seanjc@google.com> Mime-Version: 1.0 References: <20220921003201.1441511-1-seanjc@google.com> X-Mailer: git-send-email 2.37.3.968.ga6b4b080e4-goog Message-ID: <20220921003201.1441511-11-seanjc@google.com> Subject: [PATCH v4 10/12] KVM: x86: never write to memory from kvm_vcpu_check_block() From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Sean Christopherson Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Maxim Levitsky Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org From: Paolo Bonzini kvm_vcpu_check_block() is called while not in TASK_RUNNING, and therefore it cannot sleep. Writing to guest memory is therefore forbidden, but it can happen on AMD processors if kvm_check_nested_events() causes a vmexit. Fortunately, all events that are caught by kvm_check_nested_events() are also recognized by kvm_vcpu_has_events() through vendor callbacks such as kvm_x86_interrupt_allowed() or kvm_x86_ops.nested_ops->has_events(), so remove the call and postpone the actual processing to vcpu_block(). Opportunistically honor the return of kvm_check_nested_events(). KVM punted on the check in kvm_vcpu_running() because the only error path is if vmx_complete_nested_posted_interrupt() fails, in which case KVM exits to userspace with "internal error" i.e. the VM is likely dead anyways so it wasn't worth overloading the return of kvm_vcpu_running(). Add the check mostly so that KVM is consistent with itself; the return of the call via kvm_apic_accept_events()=>kvm_check_nested_events() that immediately follows _is_ checked. Reported-by: Maxim Levitsky Signed-off-by: Paolo Bonzini [sean: check and handle return of kvm_check_nested_events()] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index dcc675d4e44b..8aeacbc2bff9 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10815,6 +10815,17 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu) return 1; } + /* + * Evaluate nested events before exiting the halted state. This allows + * the halt state to be recorded properly in the VMCS12's activity + * state field (AMD does not have a similar field and a VM-Exit always + * causes a spurious wakeup from HLT). + */ + if (is_guest_mode(vcpu)) { + if (kvm_check_nested_events(vcpu) < 0) + return 0; + } + if (kvm_apic_accept_events(vcpu) < 0) return 0; switch(vcpu->arch.mp_state) { @@ -10837,9 +10848,6 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu) static inline bool kvm_vcpu_running(struct kvm_vcpu *vcpu) { - if (is_guest_mode(vcpu)) - kvm_check_nested_events(vcpu); - return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE && !vcpu->arch.apf.halted); }