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 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 B618EC433B4 for ; Mon, 10 May 2021 15:19:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96F286101B for ; Mon, 10 May 2021 15:19:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234947AbhEJPUU (ORCPT ); Mon, 10 May 2021 11:20:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234648AbhEJPSy (ORCPT ); Mon, 10 May 2021 11:18:54 -0400 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7502C06175F for ; Mon, 10 May 2021 07:48:41 -0700 (PDT) Received: by mail-qk1-x74a.google.com with SMTP id o14-20020a05620a130eb02902ea53a6ef80so11709100qkj.6 for ; Mon, 10 May 2021 07:48:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=pXf+wxEHe7OgFZweagRPX8zYZei+f+6Ny/B00rMUo8Y=; b=kdxiaN5tbOjVAa/SmKd17sTlrKysTv+CTVq7HDDGmRnKvOknp7DCMROGUuxsuYbMgJ hmtkw84JovY2kusL7hmM7XMii4LrevXiRtv528IiVINfN+2hYtl2na+zo+F2mar1TXAw R9T/wG0yWvAYo7s8p66FhH3OmJs2/X5huT7g6vc7bqnCo8GiuJnigtoAZU5DmdoWNIkv Q7Qf2vhrulnU0GRsTGQ/uO4O65nOVrcqHt+RW6Da2zzWjsIwx3QZ6ei+5MxDs3amkFR8 LgjNj0AIcCORaVvf3n6qOwhhkuYAmzqAQYvKf57wj8VuwoWfQoGnF45P2WvEd9vwlJmg 3wgg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=pXf+wxEHe7OgFZweagRPX8zYZei+f+6Ny/B00rMUo8Y=; b=nIsKkS++AkIGIFzC2w7JGVGYMpLqurN2bGiiLedpnxjg+DxKsNzOUvJ2yZqJd2OCDd ZlSmH2Hk4iLcxc+HgyWgmISrwcNWZMBvw79o71iZuxqP/GVBpvcXu5igevctqalg1p4X bY3QsakwTfoWeCGjFWkUoj2Lz5Nfwm/rK0ZusJWhog3+l4xk3m/F+UOB17FZ+Ioo9ywN 39r1fe4QCNfprUwwuH6wiizotlOCkFPrOjBrKnoeyzcpWxHDTQ89sS2U+ptOlipYjlep MHfleysQ72/pBfEkUmu8GJTo2ZeW9zo1yPrN+DQrQWTUI63HLXPjHRrvo8ePC3ppTJzQ perg== X-Gm-Message-State: AOAM531Cey4kraLBAXXE/olVUndmHztdbfYeNh2NA+mg2/O+Zz9dI1TK WSDrP+yxnU/J0snaieXAzOk4NB8Jh7GQtnkE X-Google-Smtp-Source: ABdhPJwVpttdjaULEKJDQIArIBE5aXJOXZGGdyJ3sSezasaeoOCNo+3rXOaYTQWzCE144HM78JTFpH23eeAlzni9 X-Received: from aaronlewis1.sea.corp.google.com ([2620:15c:100:202:3396:9513:fac0:8ec7]) (user=aaronlewis job=sendgmr) by 2002:a0c:e30c:: with SMTP id s12mr24109312qvl.47.1620658120802; Mon, 10 May 2021 07:48:40 -0700 (PDT) Date: Mon, 10 May 2021 07:48:33 -0700 In-Reply-To: <20210510144834.658457-1-aaronlewis@google.com> Message-Id: <20210510144834.658457-2-aaronlewis@google.com> Mime-Version: 1.0 References: <20210510144834.658457-1-aaronlewis@google.com> X-Mailer: git-send-email 2.31.1.607.g51e8a6a459-goog Subject: [PATCH v6 1/2] kvm: x86: Allow userspace to handle emulation errors From: Aaron Lewis To: david.edmondson@oracle.com, seanjc@google.com, jmattson@google.com Cc: kvm@vger.kernel.org, Aaron Lewis Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Add a fallback mechanism to the in-kernel instruction emulator that allows userspace the opportunity to process an instruction the emulator was unable to. When the in-kernel instruction emulator fails to process an instruction it will either inject a #UD into the guest or exit to userspace with exit reason KVM_INTERNAL_ERROR. This is because it does not know how to proceed in an appropriate manner. This feature lets userspace get involved to see if it can figure out a better path forward. Signed-off-by: Aaron Lewis Reviewed-by: David Edmondson --- Documentation/virt/kvm/api.rst | 19 +++++++++++++++++ arch/x86/include/asm/kvm_host.h | 6 ++++++ arch/x86/kvm/x86.c | 37 +++++++++++++++++++++++++++++---- include/uapi/linux/kvm.h | 23 ++++++++++++++++++++ tools/include/uapi/linux/kvm.h | 23 ++++++++++++++++++++ 5 files changed, 104 insertions(+), 4 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 307f2fcf1b02..17668d3e1cb7 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6233,6 +6233,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them. This capability can be used to check / enable 2nd DAWR feature provided by POWER10 processor. +7.24 KVM_CAP_EXIT_ON_EMULATION_FAILURE +-------------------------------------- + +:Architectures: x86 +:Parameters: args[0] whether the feature should be enabled or not + +When this capability is enabled, an emulation failure will result in an exit +to userspace with KVM_INTERNAL_ERROR (except when the emulator was invoked +to handle a VMware backdoor instruction). Furthermore, KVM will now provide up +to 15 instruction bytes for any exit to userspace resulting from an emulation +failure. When these exits to userspace occur use the emulation_failure struct +instead of the internal struct. They both have the same layout, but the +emulation_failure struct matches the content better. It also explicitly +defines the 'flags' field which is used to describe the fields in the struct +that are valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is +set in the 'flags' field then both 'insn_size' and 'insn_bytes' have valid data +in them.) + + 8. Other capabilities. ====================== diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3768819693e5..07235d08e976 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1049,6 +1049,12 @@ struct kvm_arch { bool exception_payload_enabled; bool bus_lock_detection_enabled; + /* + * If exit_on_emulation_error is set, and the in-kernel instruction + * emulator fails to emulate an instruction, allow userspace + * the opportunity to look at it. + */ + bool exit_on_emulation_error; /* Deflect RDMSR and WRMSR to user space when they trigger a #GP */ u32 user_space_msr_mask; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index eca63625aee4..703bcc93b129 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3771,6 +3771,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_X86_USER_SPACE_MSR: case KVM_CAP_X86_MSR_FILTER: case KVM_CAP_ENFORCE_PV_FEATURE_CPUID: + case KVM_CAP_EXIT_ON_EMULATION_FAILURE: r = 1; break; #ifdef CONFIG_KVM_XEN @@ -5357,6 +5358,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, kvm->arch.bus_lock_detection_enabled = true; r = 0; break; + case KVM_CAP_EXIT_ON_EMULATION_FAILURE: + kvm->arch.exit_on_emulation_error = cap->args[0]; + r = 0; + break; default: r = -EINVAL; break; @@ -7119,8 +7124,33 @@ void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip) } EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt); +static void prepare_emulation_failure_exit(struct kvm_vcpu *vcpu) +{ + struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt; + u32 insn_size = ctxt->fetch.end - ctxt->fetch.data; + struct kvm_run *run = vcpu->run; + + run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + run->emulation_failure.suberror = KVM_INTERNAL_ERROR_EMULATION; + run->emulation_failure.ndata = 0; + run->emulation_failure.flags = 0; + + if (insn_size) { + run->emulation_failure.ndata = 3; + run->emulation_failure.flags |= + KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES; + run->emulation_failure.insn_size = insn_size; + memset(run->emulation_failure.insn_bytes, 0x90, + sizeof(run->emulation_failure.insn_bytes)); + memcpy(run->emulation_failure.insn_bytes, + ctxt->fetch.data, insn_size); + } +} + static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type) { + struct kvm *kvm = vcpu->kvm; + ++vcpu->stat.insn_emulation_fail; trace_kvm_emulate_insn_failed(vcpu); @@ -7129,10 +7159,9 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type) return 1; } - if (emulation_type & EMULTYPE_SKIP) { - vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; - vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; - vcpu->run->internal.ndata = 0; + if (kvm->arch.exit_on_emulation_error || + (emulation_type & EMULTYPE_SKIP)) { + prepare_emulation_failure_exit(vcpu); return 0; } diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index f6afee209620..1bca5d066e3c 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -279,6 +279,9 @@ struct kvm_xen_exit { /* Encounter unexpected vm-exit reason */ #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4 +/* Flags that describe what fields in emulation_failure hold valid data. */ +#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0) + /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ struct kvm_run { /* in */ @@ -382,6 +385,25 @@ struct kvm_run { __u32 ndata; __u64 data[16]; } internal; + /* + * KVM_INTERNAL_ERROR_EMULATION + * + * "struct emulation_failure" is an overlay of "struct internal" + * that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of + * KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error + * sub-types, this struct is ABI! It also needs to be backwards + * compatible with "struct internal". Take special care that + * "ndata" is correct, that new fields are enumerated in "flags", + * and that each flag enumerates fields that are 64-bit aligned + * and sized (so that ndata+internal.data[] is valid/accurate). + */ + struct { + __u32 suberror; + __u32 ndata; + __u64 flags; + __u8 insn_size; + __u8 insn_bytes[15]; + } emulation_failure; /* KVM_EXIT_OSI */ struct { __u64 gprs[32]; @@ -1078,6 +1100,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_DIRTY_LOG_RING 192 #define KVM_CAP_X86_BUS_LOCK_EXIT 193 #define KVM_CAP_PPC_DAWR1 194 +#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 195 #ifdef KVM_CAP_IRQ_ROUTING diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h index f6afee209620..1bca5d066e3c 100644 --- a/tools/include/uapi/linux/kvm.h +++ b/tools/include/uapi/linux/kvm.h @@ -279,6 +279,9 @@ struct kvm_xen_exit { /* Encounter unexpected vm-exit reason */ #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4 +/* Flags that describe what fields in emulation_failure hold valid data. */ +#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0) + /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ struct kvm_run { /* in */ @@ -382,6 +385,25 @@ struct kvm_run { __u32 ndata; __u64 data[16]; } internal; + /* + * KVM_INTERNAL_ERROR_EMULATION + * + * "struct emulation_failure" is an overlay of "struct internal" + * that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of + * KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error + * sub-types, this struct is ABI! It also needs to be backwards + * compatible with "struct internal". Take special care that + * "ndata" is correct, that new fields are enumerated in "flags", + * and that each flag enumerates fields that are 64-bit aligned + * and sized (so that ndata+internal.data[] is valid/accurate). + */ + struct { + __u32 suberror; + __u32 ndata; + __u64 flags; + __u8 insn_size; + __u8 insn_bytes[15]; + } emulation_failure; /* KVM_EXIT_OSI */ struct { __u64 gprs[32]; @@ -1078,6 +1100,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_DIRTY_LOG_RING 192 #define KVM_CAP_X86_BUS_LOCK_EXIT 193 #define KVM_CAP_PPC_DAWR1 194 +#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 195 #ifdef KVM_CAP_IRQ_ROUTING -- 2.31.1.607.g51e8a6a459-goog