From mboxrd@z Thu Jan 1 00:00:00 1970 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 780EEC32772 for ; Mon, 22 Aug 2022 17:07:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237171AbiHVRHQ (ORCPT ); Mon, 22 Aug 2022 13:07:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235876AbiHVRHK (ORCPT ); Mon, 22 Aug 2022 13:07:10 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E707242AC9 for ; Mon, 22 Aug 2022 10:07:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1661188023; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=OZupmRZtcUtlH4659i6zFhdu2zNlFDA9+3SfaNsY/Ro=; b=e/7NtnVV0FM0u6EUyWMIhXw/I+35v+LseFcqxyZj7AAzlPiKJ/9VE/XDdlNv1jx4Yy6jTI MqdaP4ArErfYFWqf0a9481vZvLp+IIITzSpsVxvzi0hxJqA2g1V5CMNt2dZjiJpRWznxfH GNtSBVVwd6c0xAiEClxFEfPe8dOl5kc= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-261-NqFD413gOXqFk3OTVAUTbA-1; Mon, 22 Aug 2022 13:06:59 -0400 X-MC-Unique: NqFD413gOXqFk3OTVAUTbA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6671485A585; Mon, 22 Aug 2022 17:06:59 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 44529945D0; Mon, 22 Aug 2022 17:06:59 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: mlevitsk@redhat.com, seanjc@google.com Subject: [PATCH v3 0/7] KVM: x86: never write to memory from kvm_vcpu_check_block Date: Mon, 22 Aug 2022 13:06:52 -0400 Message-Id: <20220822170659.2527086-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The following backtrace: [ 1355.807187] kvm_vcpu_map+0x159/0x190 [kvm] [ 1355.807628] nested_svm_vmexit+0x4c/0x7f0 [kvm_amd] [ 1355.808036] ? kvm_vcpu_block+0x54/0xa0 [kvm] [ 1355.808450] svm_check_nested_events+0x97/0x390 [kvm_amd] [ 1355.808920] kvm_check_nested_events+0x1c/0x40 [kvm] [ 1355.809396] kvm_arch_vcpu_runnable+0x4e/0x190 [kvm] [ 1355.809892] kvm_vcpu_check_block+0x4f/0x100 [kvm] [ 1355.811259] kvm_vcpu_block+0x6b/0xa0 [kvm] can occur due to kmap being called in non-sleepable (!TASK_RUNNING) context. The fix is to extend kvm_x86_ops->nested_ops.hv_timer_pending() to cover all events not already checked in kvm_arch_vcpu_is_runnable(), and then get rid of the annoying (and wrong) call to kvm_check_nested_events() from kvm_vcpu_check_block(). Beware, this is not a complete fix, because kvm_guest_apic_has_interrupt() might still _read_ memory from non-sleepable context. The fix here is probably to make kvm_arch_vcpu_is_runnable() return -EAGAIN, and in that case do a round of kvm_vcpu_check_block() polling in sleepable context. Nevertheless, it is a good start as it pushes the vmexit into vcpu_block(). The series also does a small cleanup pass on kvm_vcpu_check_block(), removing KVM_REQ_UNHALT in favor of simply calling kvm_arch_vcpu_runnable() again. Now that kvm_check_nested_events() is not called anymore by kvm_arch_vcpu_runnable(), it is much easier to see that KVM will never consume the event that caused kvm_vcpu_has_events() to return true, and therefore it is safe to evaluate it again. The alternative of propagating the return value of kvm_arch_vcpu_runnable() up to kvm_vcpu_{block,halt}() is inferior because it does not quite get right the edge cases where the vCPU becomes runnable right before schedule() or right after kvm_vcpu_check_block(). While these edge cases are unlikely to truly matter in practice, it is also pointless to get them "wrong". Paolo v2->v3: do not propagate the return value of kvm_arch_vcpu_runnable() up to kvm_vcpu_{block,halt}() move and reformat the comment in vcpu_block() move KVM_REQ_UNHALT removal last Paolo Bonzini (6): KVM: x86: check validity of argument to KVM_SET_MP_STATE KVM: x86: make vendor code check for all nested events KVM: x86: lapic does not have to process INIT if it is blocked KVM: x86: never write to memory from kvm_vcpu_check_block KVM: mips, x86: do not rely on KVM_REQ_UNHALT KVM: remove KVM_REQ_UNHALT Sean Christopherson (1): KVM: nVMX: Make an event request when pending an MTF nested VM-Exit Documentation/virt/kvm/vcpu-requests.rst | 28 +------------ arch/arm64/kvm/arm.c | 1 - arch/mips/kvm/emulate.c | 6 +-- arch/powerpc/kvm/book3s_pr.c | 1 - arch/powerpc/kvm/book3s_pr_papr.c | 1 - arch/powerpc/kvm/booke.c | 1 - arch/powerpc/kvm/powerpc.c | 1 - arch/riscv/kvm/vcpu_insn.c | 1 - arch/s390/kvm/kvm-s390.c | 2 - arch/x86/include/asm/kvm_host.h | 3 +- arch/x86/kvm/i8259.c | 4 +- arch/x86/kvm/lapic.h | 2 +- arch/x86/kvm/vmx/nested.c | 9 +++- arch/x86/kvm/vmx/vmx.c | 6 ++- arch/x86/kvm/x86.c | 53 ++++++++++++++++++------ arch/x86/kvm/x86.h | 5 --- arch/x86/kvm/xen.c | 1 - include/linux/kvm_host.h | 3 +- virt/kvm/kvm_main.c | 4 +- 19 files changed, 63 insertions(+), 69 deletions(-) -- 2.31.1