From patchwork Sat Jan 23 00:03:33 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12040969 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9CF10C433DB for ; Sat, 23 Jan 2021 00:07:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D70D23B75 for ; Sat, 23 Jan 2021 00:07:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726224AbhAWAGu (ORCPT ); Fri, 22 Jan 2021 19:06:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35186 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726580AbhAWAEV (ORCPT ); Fri, 22 Jan 2021 19:04:21 -0500 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF2C0C061794 for ; Fri, 22 Jan 2021 16:03:40 -0800 (PST) Received: by mail-qv1-xf4a.google.com with SMTP id j24so5042450qvg.8 for ; Fri, 22 Jan 2021 16:03:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:to:cc; bh=kAWuaESsc2ZEzrFWxj8fVnjbm69FHkEio6nEEHrCqso=; b=vPheHINMwQ7x81BAVOdlxaLV9ZmxEAUxLwRQEterkex73h1GF1e0JJOYRw917hMlJS FjIRezaFCAn8JbR+AXZr+AcnJ3CebTq465UDw75KfzxtM4TRaQCtV3gq/CRx8YeCNoTw RbNr1fj2/TsWw0R3YPkIvv4sqI1fwZp+G5aM9StcUIGhKnUYY39MI131/gVsHTV6uNvF Xxuz6WK7rAVqq1FamjRJaBpl2CNt4D8B41KeEa98aaDnHtwvVlQ9oBcKS/1WSS5cN9Uv D6/FDFzy3zLDM2Hhkk8PnrXd1cGoCSjw4d5gVOxUV5JqjSs9EaOTNab2/rhN0kCRkCb2 3j1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:to:cc; bh=kAWuaESsc2ZEzrFWxj8fVnjbm69FHkEio6nEEHrCqso=; b=a0SCBHU60VcVtVZRX4nUPLBbVr4fl3Gfc5UiEmuz7Go4gVeGoc2JyTsygQyAF1jpAE T71yn4Oi1pXvERSpBvG7gUMB4lZNsGP2fSTQXTiUO3kvxFiv3YYu2eSGerS/4fwbfDpQ Ego9BLT5aOWBsh1m3IdmAviEeVrcu1Ut5no9nKFaIyQEaIMQo5wUF/8zSHgnVnE9pOgG sOaQ62yE39TlACT3BJqGmSEfbtQXcrHo5sUj0o1Fcf13bn1bF5fovmbC4NjSSlh1/euO nnqkqKKawtowZ0jCbLqWtp0DX95qoT6wRw/qtXO8+ainogDRCZxo8Wi2BBU8kmcVQMuZ TDFA== X-Gm-Message-State: AOAM532BE88QotvyytwEPl6AqsZtXD2/wCRFUSTG0EkHEcdXSC0OCLSJ 2OXYbxjhCIoKmkVBPKM116mof1XYoV0= X-Google-Smtp-Source: ABdhPJzIaxvGYNmKQCnDZF49b4i+ePgAT9JFDk8xFGgl9hTFC178lmVaRjBqNudM58fgQn4oA9eD1zI+Xk8= Sender: "seanjc via sendgmr" X-Received: from seanjc798194.pdx.corp.google.com ([2620:15c:f:10:1ea0:b8ff:fe73:50f5]) (user=seanjc job=sendgmr) by 2002:ad4:5904:: with SMTP id ez4mr6848541qvb.30.1611360220039; Fri, 22 Jan 2021 16:03:40 -0800 (PST) Reply-To: Sean Christopherson Date: Fri, 22 Jan 2021 16:03:33 -0800 In-Reply-To: <20210123000334.3123628-1-seanjc@google.com> Message-Id: <20210123000334.3123628-2-seanjc@google.com> Mime-Version: 1.0 References: <20210123000334.3123628-1-seanjc@google.com> X-Mailer: git-send-email 2.30.0.280.ga3ce27912f-goog Subject: [PATCH 1/2] KVM: x86: Remove obsolete disabling of page faults in kvm_arch_vcpu_put() From: Sean Christopherson To: Paolo Bonzini Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Remove the disabling of page faults across kvm_steal_time_set_preempted() as KVM now accesses the steal time struct (shared with the guest) via a cached mapping (see commit b043138246a4, "x86/KVM: Make sure KVM_VCPU_FLUSH_TLB flag is not missed".) The cache lookup is flagged as atomic, thus it would be a bug if KVM tried to resolve a new pfn, i.e. we want the splat that would be reached via might_fault(). Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9a8969a6dd06..3f4b09d9f25b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4031,15 +4031,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) if (vcpu->preempted && !vcpu->arch.guest_state_protected) vcpu->arch.preempted_in_kernel = !kvm_x86_ops.get_cpl(vcpu); - /* - * Disable page faults because we're in atomic context here. - * kvm_write_guest_offset_cached() would call might_fault() - * that relies on pagefault_disable() to tell if there's a - * bug. NOTE: the write to guest memory may not go through if - * during postcopy live migration or if there's heavy guest - * paging. - */ - pagefault_disable(); /* * kvm_memslots() will be called by * kvm_write_guest_offset_cached() so take the srcu lock. @@ -4047,7 +4038,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) idx = srcu_read_lock(&vcpu->kvm->srcu); kvm_steal_time_set_preempted(vcpu); srcu_read_unlock(&vcpu->kvm->srcu, idx); - pagefault_enable(); kvm_x86_ops.vcpu_put(vcpu); vcpu->arch.last_host_tsc = rdtsc(); /*