From patchwork Mon Aug 3 21:14:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Graf X-Patchwork-Id: 11699185 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C8D3B14DD for ; Mon, 3 Aug 2020 21:15:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0699422CA1 for ; Mon, 3 Aug 2020 21:15:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="KbV9GEfn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729211AbgHCVO7 (ORCPT ); Mon, 3 Aug 2020 17:14:59 -0400 Received: from smtp-fw-9102.amazon.com ([207.171.184.29]:7237 "EHLO smtp-fw-9102.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729177AbgHCVO5 (ORCPT ); Mon, 3 Aug 2020 17:14:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1596489294; x=1628025294; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=qdwzlFqSs011PwSP9OouF95I4cXaDgftnH/m6CTUpvk=; b=KbV9GEfnK2FslQtXGMJGDN5oo30IBatyQljE8k3Nvjdw75O5p7hghnQL 0/BFBMyuufRKt35EOejV2XolAyZu9aAO0hUASZw4DdfQ9RLkmP/ih5AZp 7qQQRfrj1WIZr+bTTf47Ja4lpwLjx4XHOR2Nh762mGhjQw9pTYDYknLij g=; IronPort-SDR: w8j/mdB/Oq3LegnGL0ggI3TobcuAA4294JqZ7x8zT/NZz/njjYPK1bR5I/yFCieugjkC051f87 S+9eeJwEfzTw== X-IronPort-AV: E=Sophos;i="5.75,431,1589241600"; d="scan'208";a="65228583" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-1e-303d0b0e.us-east-1.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-9102.sea19.amazon.com with ESMTP; 03 Aug 2020 21:14:42 +0000 Received: from EX13MTAUWC001.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan2.iad.amazon.com [10.40.159.162]) by email-inbound-relay-1e-303d0b0e.us-east-1.amazon.com (Postfix) with ESMTPS id CB195A1F9A; Mon, 3 Aug 2020 21:14:38 +0000 (UTC) Received: from EX13D20UWC001.ant.amazon.com (10.43.162.244) by EX13MTAUWC001.ant.amazon.com (10.43.162.135) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 Aug 2020 21:14:38 +0000 Received: from u79c5a0a55de558.ant.amazon.com (10.43.161.145) by EX13D20UWC001.ant.amazon.com (10.43.162.244) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 Aug 2020 21:14:34 +0000 From: Alexander Graf To: Paolo Bonzini CC: Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , "Joerg Roedel" , KarimAllah Raslan , Aaron Lewis , , , Subject: [PATCH v4 1/3] KVM: x86: Deflect unknown MSR accesses to user space Date: Mon, 3 Aug 2020 23:14:21 +0200 Message-ID: <20200803211423.29398-2-graf@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200803211423.29398-1-graf@amazon.com> References: <20200803211423.29398-1-graf@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.161.145] X-ClientProxiedBy: EX13D36UWB001.ant.amazon.com (10.43.161.84) To EX13D20UWC001.ant.amazon.com (10.43.162.244) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org MSRs are weird. Some of them are normal control registers, such as EFER. Some however are registers that really are model specific, not very interesting to virtualization workloads, and not performance critical. Others again are really just windows into package configuration. Out of these MSRs, only the first category is necessary to implement in kernel space. Rarely accessed MSRs, MSRs that should be fine tunes against certain CPU models and MSRs that contain information on the package level are much better suited for user space to process. However, over time we have accumulated a lot of MSRs that are not the first category, but still handled by in-kernel KVM code. This patch adds a generic interface to handle WRMSR and RDMSR from user space. With this, any future MSR that is part of the latter categories can be handled in user space. Furthermore, it allows us to replace the existing "ignore_msrs" logic with something that applies per-VM rather than on the full system. That way you can run productive VMs in parallel to experimental ones where you don't care about proper MSR handling. Signed-off-by: Alexander Graf Reviewed-by: Jim Mattson --- v1 -> v2: - s/ETRAP_TO_USER_SPACE/ENOENT/g - deflect all #GP injection events to user space, not just unknown MSRs. That was we can also deflect allowlist errors later - fix emulator case v2 -> v3: - return r if r == X86EMUL_IO_NEEDED - s/KVM_EXIT_RDMSR/KVM_EXIT_X86_RDMSR/g - s/KVM_EXIT_WRMSR/KVM_EXIT_X86_WRMSR/g - Use complete_userspace_io logic instead of reply field - Simplify trapping code v3 -> v4: - Mention exit reasons in re-enter mandatory section of API documentation - Clear padding bytes - Generalize get/set deflect functions - Remove redundant pending_user_msr field --- Documentation/virt/kvm/api.rst | 66 +++++++++++++++++++- arch/x86/include/asm/kvm_host.h | 3 + arch/x86/kvm/emulate.c | 18 +++++- arch/x86/kvm/x86.c | 106 ++++++++++++++++++++++++++++++-- include/trace/events/kvm.h | 2 +- include/uapi/linux/kvm.h | 10 +++ 6 files changed, 196 insertions(+), 9 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 320788f81a05..2ca38649b3d4 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -4861,8 +4861,8 @@ to the byte array. .. note:: - For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR and - KVM_EXIT_EPR the corresponding + For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR, + KVM_EXIT_EPR, KVM_EXIT_X86_RDMSR and KVM_EXIT_X86_WRMSR the corresponding operations are complete (and guest state is consistent) only after userspace has re-entered the kernel with KVM_RUN. The kernel side will first finish @@ -5155,6 +5155,35 @@ Note that KVM does not skip the faulting instruction as it does for KVM_EXIT_MMIO, but userspace has to emulate any change to the processing state if it decides to decode and emulate the instruction. +:: + + /* KVM_EXIT_X86_RDMSR / KVM_EXIT_X86_WRMSR */ + struct { + __u8 error; + __u8 pad[3]; + __u32 index; + __u64 data; + } msr; + +Used on x86 systems. When the VM capability KVM_CAP_X86_USER_SPACE_MSR is +enabled, MSR accesses to registers that would invoke a #GP by KVM kernel code +will instead trigger a KVM_EXIT_X86_RDMSR exit for reads and KVM_EXIT_X86_WRMSR +exit for writes. + +For KVM_EXIT_X86_RDMSR, the "index" field tells user space which MSR the guest +wants to read. To respond to this request with a successful read, user space +writes the respective data into the "data" field and must continue guest +execution to ensure the read data is transferred into guest register state. + +If the RDMSR request was unsuccessful, user space indicates that with a "1" in +the "error" field. This will inject a #GP into the guest when the VCPU is +executed again. + +For KVM_EXIT_X86_WRMSR, the "index" field tells user space which MSR the guest +wants to write. Once finished processing the event, user space must continue +vCPU execution. If the MSR write was unsuccessful, user space also sets the +"error" field to "1". + :: /* Fix the size of the union. */ @@ -5844,6 +5873,28 @@ controlled by the kvm module parameter halt_poll_ns. This capability allows the maximum halt time to specified on a per-VM basis, effectively overriding the module parameter for the target VM. +7.21 KVM_CAP_X86_USER_SPACE_MSR +------------------------------- + +:Architectures: x86 +:Target: VM +:Parameters: args[0] is 1 if user space MSR handling is enabled, 0 otherwise +:Returns: 0 on success; -1 on error + +This capability enables trapping of #GP invoking RDMSR and WRMSR instructions +into user space. + +When a guest requests to read or write an MSR, KVM may not implement all MSRs +that are relevant to a respective system. It also does not differentiate by +CPU type. + +To allow more fine grained control over MSR handling, user space may enable +this capability. With it enabled, MSR accesses that would usually trigger +a #GP event inside the guest by KVM will instead trigger KVM_EXIT_X86_RDMSR +and KVM_EXIT_X86_WRMSR exit notifications which user space can then handle to +implement model specific MSR handling and/or user notifications to inform +a user that an MSR was not handled. + 8. Other capabilities. ====================== @@ -6151,3 +6202,14 @@ KVM can therefore start protected VMs. This capability governs the KVM_S390_PV_COMMAND ioctl and the KVM_MP_STATE_LOAD MP_STATE. KVM_SET_MP_STATE can fail for protected guests when the state change is invalid. + +8.24 KVM_CAP_X86_USER_SPACE_MSR +---------------------------- + +:Architectures: x86 + +This capability indicates that KVM supports deflection of MSR reads and +writes to user space. It can be enabled on a VM level. If enabled, MSR +accesses that would usually trigger a #GP by KVM into the guest will +instead get bounced to user space through the KVM_EXIT_X86_RDMSR and +KVM_EXIT_X86_WRMSR exit notifications. diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index be5363b21540..2f2307e71342 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1002,6 +1002,9 @@ struct kvm_arch { bool guest_can_read_msr_platform_info; bool exception_payload_enabled; + /* Deflect RDMSR and WRMSR to user space when they trigger a #GP */ + bool user_space_msr_enabled; + struct kvm_pmu_event_filter *pmu_event_filter; struct task_struct *nx_lpage_recovery_thread; }; diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index d0e2825ae617..744ab9c92b73 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3689,11 +3689,18 @@ static int em_dr_write(struct x86_emulate_ctxt *ctxt) static int em_wrmsr(struct x86_emulate_ctxt *ctxt) { + u64 msr_index = reg_read(ctxt, VCPU_REGS_RCX); u64 msr_data; + int r; msr_data = (u32)reg_read(ctxt, VCPU_REGS_RAX) | ((u64)reg_read(ctxt, VCPU_REGS_RDX) << 32); - if (ctxt->ops->set_msr(ctxt, reg_read(ctxt, VCPU_REGS_RCX), msr_data)) + r = ctxt->ops->set_msr(ctxt, msr_index, msr_data); + + if (r == X86EMUL_IO_NEEDED) + return r; + + if (r) return emulate_gp(ctxt, 0); return X86EMUL_CONTINUE; @@ -3701,9 +3708,16 @@ static int em_wrmsr(struct x86_emulate_ctxt *ctxt) static int em_rdmsr(struct x86_emulate_ctxt *ctxt) { + u64 msr_index = reg_read(ctxt, VCPU_REGS_RCX); u64 msr_data; + int r; + + r = ctxt->ops->get_msr(ctxt, msr_index, &msr_data); + + if (r == X86EMUL_IO_NEEDED) + return r; - if (ctxt->ops->get_msr(ctxt, reg_read(ctxt, VCPU_REGS_RCX), &msr_data)) + if (r) return emulate_gp(ctxt, 0); *reg_write(ctxt, VCPU_REGS_RAX) = (u32)msr_data; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 88c593f83b28..e1139124350f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1549,12 +1549,75 @@ int kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data) } EXPORT_SYMBOL_GPL(kvm_set_msr); +static int complete_emulated_msr(struct kvm_vcpu *vcpu, bool is_read) +{ + if (vcpu->run->msr.error) { + kvm_inject_gp(vcpu, 0); + } else if (is_read) { + kvm_rax_write(vcpu, (u32)vcpu->run->msr.data); + kvm_rdx_write(vcpu, vcpu->run->msr.data >> 32); + } + + return kvm_skip_emulated_instruction(vcpu); +} + +static int complete_emulated_rdmsr(struct kvm_vcpu *vcpu) +{ + return complete_emulated_msr(vcpu, true); +} + +static int complete_emulated_wrmsr(struct kvm_vcpu *vcpu) +{ + return complete_emulated_msr(vcpu, false); +} + +static int kvm_msr_user_space(struct kvm_vcpu *vcpu, u32 index, + u32 exit_reason, u64 data, + int (*completion)(struct kvm_vcpu *vcpu)) +{ + if (!vcpu->kvm->arch.user_space_msr_enabled) + return 0; + + vcpu->run->exit_reason = exit_reason; + vcpu->run->msr.error = 0; + vcpu->run->msr.pad[0] = 0; + vcpu->run->msr.pad[1] = 0; + vcpu->run->msr.pad[2] = 0; + vcpu->run->msr.index = index; + vcpu->run->msr.data = data; + vcpu->arch.complete_userspace_io = completion; + + return 1; +} + +static int kvm_get_msr_user_space(struct kvm_vcpu *vcpu, u32 index) +{ + return kvm_msr_user_space(vcpu, index, KVM_EXIT_X86_RDMSR, 0, + complete_emulated_rdmsr); +} + +static int kvm_set_msr_user_space(struct kvm_vcpu *vcpu, u32 index, u64 data) +{ + return kvm_msr_user_space(vcpu, index, KVM_EXIT_X86_WRMSR, data, + complete_emulated_wrmsr); +} + int kvm_emulate_rdmsr(struct kvm_vcpu *vcpu) { u32 ecx = kvm_rcx_read(vcpu); u64 data; + int r; - if (kvm_get_msr(vcpu, ecx, &data)) { + r = kvm_get_msr(vcpu, ecx, &data); + + /* MSR read failed? See if we should ask user space */ + if (r && kvm_get_msr_user_space(vcpu, ecx)) { + /* Bounce to user space */ + return 0; + } + + /* MSR read failed? Inject a #GP */ + if (r) { trace_kvm_msr_read_ex(ecx); kvm_inject_gp(vcpu, 0); return 1; @@ -1572,8 +1635,18 @@ int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu) { u32 ecx = kvm_rcx_read(vcpu); u64 data = kvm_read_edx_eax(vcpu); + int r; + + r = kvm_set_msr(vcpu, ecx, data); + + /* MSR write failed? See if we should ask user space */ + if (r && kvm_set_msr_user_space(vcpu, ecx, data)) { + /* Bounce to user space */ + return 0; + } - if (kvm_set_msr(vcpu, ecx, data)) { + /* MSR write failed? Inject a #GP */ + if (r) { trace_kvm_msr_write_ex(ecx, data); kvm_inject_gp(vcpu, 0); return 1; @@ -3476,6 +3549,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_MSR_PLATFORM_INFO: case KVM_CAP_EXCEPTION_PAYLOAD: case KVM_CAP_SET_GUEST_DEBUG: + case KVM_CAP_X86_USER_SPACE_MSR: r = 1; break; case KVM_CAP_SYNC_REGS: @@ -4990,6 +5064,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, kvm->arch.exception_payload_enabled = cap->args[0]; r = 0; break; + case KVM_CAP_X86_USER_SPACE_MSR: + kvm->arch.user_space_msr_enabled = cap->args[0]; + r = 0; + break; default: r = -EINVAL; break; @@ -6319,13 +6397,33 @@ static void emulator_set_segment(struct x86_emulate_ctxt *ctxt, u16 selector, static int emulator_get_msr(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 *pdata) { - return kvm_get_msr(emul_to_vcpu(ctxt), msr_index, pdata); + struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); + int r; + + r = kvm_get_msr(vcpu, msr_index, pdata); + + if (r && kvm_get_msr_user_space(vcpu, msr_index)) { + /* Bounce to user space */ + return X86EMUL_IO_NEEDED; + } + + return r; } static int emulator_set_msr(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 data) { - return kvm_set_msr(emul_to_vcpu(ctxt), msr_index, data); + struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); + int r; + + r = kvm_set_msr(emul_to_vcpu(ctxt), msr_index, data); + + if (r && kvm_set_msr_user_space(vcpu, msr_index, data)) { + /* Bounce to user space */ + return X86EMUL_IO_NEEDED; + } + + return r; } static u64 emulator_get_smbase(struct x86_emulate_ctxt *ctxt) diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h index 9417a34aad08..26cfb0fa8e7e 100644 --- a/include/trace/events/kvm.h +++ b/include/trace/events/kvm.h @@ -17,7 +17,7 @@ ERSN(NMI), ERSN(INTERNAL_ERROR), ERSN(OSI), ERSN(PAPR_HCALL), \ ERSN(S390_UCONTROL), ERSN(WATCHDOG), ERSN(S390_TSCH), ERSN(EPR),\ ERSN(SYSTEM_EVENT), ERSN(S390_STSI), ERSN(IOAPIC_EOI), \ - ERSN(HYPERV), ERSN(ARM_NISV) + ERSN(HYPERV), ERSN(ARM_NISV), ERSN(X86_RDMSR), ERSN(X86_WRMSR) TRACE_EVENT(kvm_userspace_exit, TP_PROTO(__u32 reason, int errno), diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 4fdf30316582..13fc7de1eb50 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -248,6 +248,8 @@ struct kvm_hyperv_exit { #define KVM_EXIT_IOAPIC_EOI 26 #define KVM_EXIT_HYPERV 27 #define KVM_EXIT_ARM_NISV 28 +#define KVM_EXIT_X86_RDMSR 29 +#define KVM_EXIT_X86_WRMSR 30 /* For KVM_EXIT_INTERNAL_ERROR */ /* Emulate instruction failed. */ @@ -412,6 +414,13 @@ struct kvm_run { __u64 esr_iss; __u64 fault_ipa; } arm_nisv; + /* KVM_EXIT_X86_RDMSR / KVM_EXIT_X86_WRMSR */ + struct { + __u8 error; + __u8 pad[3]; + __u32 index; + __u64 data; + } msr; /* Fix the size of the union. */ char padding[256]; }; @@ -1031,6 +1040,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_PPC_SECURE_GUEST 181 #define KVM_CAP_HALT_POLL 182 #define KVM_CAP_ASYNC_PF_INT 183 +#define KVM_CAP_X86_USER_SPACE_MSR 184 #ifdef KVM_CAP_IRQ_ROUTING From patchwork Mon Aug 3 21:14:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Graf X-Patchwork-Id: 11699183 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 069D913B1 for ; Mon, 3 Aug 2020 21:14:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A1CE22C9F for ; Mon, 3 Aug 2020 21:14:54 +0000 (UTC) Authentication-Results: mail.kernel.org; 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d="scan'208";a="45882896" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-1d-5dd976cd.us-east-1.amazon.com) ([10.43.8.6]) by smtp-border-fw-out-4101.iad4.amazon.com with ESMTP; 03 Aug 2020 21:14:46 +0000 Received: from EX13MTAUWC001.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan2.iad.amazon.com [10.40.159.162]) by email-inbound-relay-1d-5dd976cd.us-east-1.amazon.com (Postfix) with ESMTPS id 5625CA2401; Mon, 3 Aug 2020 21:14:42 +0000 (UTC) Received: from EX13D20UWC001.ant.amazon.com (10.43.162.244) by EX13MTAUWC001.ant.amazon.com (10.43.162.135) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 Aug 2020 21:14:41 +0000 Received: from u79c5a0a55de558.ant.amazon.com (10.43.161.145) by EX13D20UWC001.ant.amazon.com (10.43.162.244) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 Aug 2020 21:14:38 +0000 From: Alexander Graf To: Paolo Bonzini CC: Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , "Joerg Roedel" , KarimAllah Raslan , Aaron Lewis , , , Subject: [PATCH v4 2/3] KVM: x86: Introduce allow list for MSR emulation Date: Mon, 3 Aug 2020 23:14:22 +0200 Message-ID: <20200803211423.29398-3-graf@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200803211423.29398-1-graf@amazon.com> References: <20200803211423.29398-1-graf@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.161.145] X-ClientProxiedBy: EX13D36UWB001.ant.amazon.com (10.43.161.84) To EX13D20UWC001.ant.amazon.com (10.43.162.244) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org It's not desireable to have all MSRs always handled by KVM kernel space. Some MSRs would be useful to handle in user space to either emulate behavior (like uCode updates) or differentiate whether they are valid based on the CPU model. To allow user space to specify which MSRs it wants to see handled by KVM, this patch introduces a new ioctl to push allow lists of bitmaps into KVM. Based on these bitmaps, KVM can then decide whether to reject MSR access. With the addition of KVM_CAP_X86_USER_SPACE_MSR it can also deflect the denied MSR events to user space to operate on. If no allowlist is populated, MSR handling stays identical to before. Signed-off-by: KarimAllah Ahmed Signed-off-by: Alexander Graf --- v2 -> v3: - document flags for KVM_X86_ADD_MSR_ALLOWLIST - generalize exit path, always unlock when returning - s/KVM_CAP_ADD_MSR_ALLOWLIST/KVM_CAP_X86_MSR_ALLOWLIST/g - Add KVM_X86_CLEAR_MSR_ALLOWLIST v3 -> v4: - lock allow check and clearing - free bitmaps on clear --- Documentation/virt/kvm/api.rst | 91 +++++++++++++++++++ arch/x86/include/asm/kvm_host.h | 10 +++ arch/x86/include/uapi/asm/kvm.h | 15 ++++ arch/x86/kvm/x86.c | 153 ++++++++++++++++++++++++++++++++ include/uapi/linux/kvm.h | 5 ++ 5 files changed, 274 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 2ca38649b3d4..9cb36060f61c 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -4697,6 +4697,82 @@ KVM_PV_VM_VERIFY Verify the integrity of the unpacked image. Only if this succeeds, KVM is allowed to start protected VCPUs. +4.126 KVM_X86_ADD_MSR_ALLOWLIST +------------------------------- + +:Capability: KVM_CAP_X86_MSR_ALLOWLIST +:Architectures: x86 +:Type: vm ioctl +:Parameters: struct kvm_msr_allowlist +:Returns: 0 on success, < 0 on error + +:: + + struct kvm_msr_allowlist { + __u32 flags; + __u32 nmsrs; /* number of msrs in bitmap */ + __u32 base; /* base address for the MSRs bitmap */ + __u32 pad; + + __u8 bitmap[0]; /* a set bit allows that the operation set in flags */ + }; + +flags values: + +KVM_MSR_ALLOW_READ + + Filter read accesses to MSRs using the given bitmap. A 0 in the bitmap + indicates that a read should immediately fail, while a 1 indicates that + a read should be handled by the normal KVM MSR emulation logic. + +KVM_MSR_ALLOW_WRITE + + Filter write accesses to MSRs using the given bitmap. A 0 in the bitmap + indicates that a write should immediately fail, while a 1 indicates that + a write should be handled by the normal KVM MSR emulation logic. + +KVM_MSR_ALLOW_READ | KVM_MSR_ALLOW_WRITE + + Filter booth read and write accesses to MSRs using the given bitmap. A 0 + in the bitmap indicates that both reads and writes should immediately fail, + while a 1 indicates that reads and writes should be handled by the normal + KVM MSR emulation logic. + +This ioctl allows user space to define a set of bitmaps of MSR ranges to +specify whether a certain MSR access is allowed or not. + +If this ioctl has never been invoked, MSR accesses are not guarded and the +old KVM in-kernel emulation behavior is fully preserved. + +As soon as the first allow list was specified, only allowed MSR accesses +are permitted inside of KVM's MSR code. + +Each allowlist specifies a range of MSRs to potentially allow access on. +The range goes from MSR index [base .. base+nmsrs]. The flags field +indicates whether reads, writes or both reads and writes are permitted +by setting a 1 bit in the bitmap for the corresponding MSR index. + +If an MSR access is not permitted through the allow list, it generates a +#GP inside the guest. When combined with KVM_CAP_X86_USER_SPACE_MSR, that +allows user space to deflect and potentially handle various MSR accesses +into user space. + +4.124 KVM_X86_CLEAR_MSR_ALLOWLIST +--------------------------------- + +:Capability: KVM_CAP_X86_MSR_ALLOWLIST +:Architectures: x86 +:Type: vcpu ioctl +:Parameters: none +:Returns: 0 + +This ioctl resets all internal MSR allow lists. After this call, no allow +list is present and the guest would execute as if no allow lists were set, +so all MSRs are considered allowed and thus handled by the in-kernel MSR +emulation logic. + +No vCPU may be in running state when calling this ioctl. + 5. The kvm_run structure ======================== @@ -6213,3 +6289,18 @@ writes to user space. It can be enabled on a VM level. If enabled, MSR accesses that would usually trigger a #GP by KVM into the guest will instead get bounced to user space through the KVM_EXIT_X86_RDMSR and KVM_EXIT_X86_WRMSR exit notifications. + +8.25 KVM_CAP_X86_MSR_ALLOWLIST +------------------------------ + +:Architectures: x86 + +This capability indicates that KVM supports emulation of only select MSR +registers. With this capability exposed, KVM exports two new VM ioctls: +KVM_X86_ADD_MSR_ALLOWLIST which user space can call to specify bitmaps of MSR +ranges that KVM should emulate in kernel space and KVM_X86_CLEAR_MSR_ALLOWLIST +which user space can call to remove all MSR allow lists from the VM context. + +In combination with KVM_CAP_X86_USER_SPACE_MSR, this allows user space to +trap and emulate MSRs that are outside of the scope of KVM as well as +limit the attack surface on KVM's MSR emulation code. diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 2f2307e71342..4b1ff7cb848f 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -901,6 +901,13 @@ struct kvm_hv { struct kvm_hv_syndbg hv_syndbg; }; +struct msr_bitmap_range { + u32 flags; + u32 nmsrs; + u32 base; + unsigned long *bitmap; +}; + enum kvm_irqchip_mode { KVM_IRQCHIP_NONE, KVM_IRQCHIP_KERNEL, /* created with KVM_CREATE_IRQCHIP */ @@ -1005,6 +1012,9 @@ struct kvm_arch { /* Deflect RDMSR and WRMSR to user space when they trigger a #GP */ bool user_space_msr_enabled; + struct msr_bitmap_range msr_allowlist_ranges[10]; + int msr_allowlist_ranges_count; + struct kvm_pmu_event_filter *pmu_event_filter; struct task_struct *nx_lpage_recovery_thread; }; diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h index 0780f97c1850..c33fb1d72d52 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -192,6 +192,21 @@ struct kvm_msr_list { __u32 indices[0]; }; +#define KVM_MSR_ALLOW_READ (1 << 0) +#define KVM_MSR_ALLOW_WRITE (1 << 1) + +/* Maximum size of the of the bitmap in bytes */ +#define KVM_MSR_ALLOWLIST_MAX_LEN 0x600 + +/* for KVM_X86_ADD_MSR_ALLOWLIST */ +struct kvm_msr_allowlist { + __u32 flags; + __u32 nmsrs; /* number of msrs in bitmap */ + __u32 base; /* base address for the MSRs bitmap */ + __u32 pad; + + __u8 bitmap[0]; /* a set bit allows that the operation set in flags */ +}; struct kvm_cpuid_entry { __u32 function; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index e1139124350f..25e58ceb19de 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1472,6 +1472,38 @@ void kvm_enable_efer_bits(u64 mask) } EXPORT_SYMBOL_GPL(kvm_enable_efer_bits); +static bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type) +{ + struct kvm *kvm = vcpu->kvm; + struct msr_bitmap_range *ranges = kvm->arch.msr_allowlist_ranges; + u32 count = kvm->arch.msr_allowlist_ranges_count; + u32 i; + bool r = false; + + /* MSR allowlist not set up, allow everything */ + if (!count) + return true; + + /* Prevent collision with clear_msr_allowlist */ + mutex_lock(&kvm->lock); + + for (i = 0; i < count; i++) { + u32 start = ranges[i].base; + u32 end = start + ranges[i].nmsrs; + u32 flags = ranges[i].flags; + unsigned long *bitmap = ranges[i].bitmap; + + if ((index >= start) && (index < end) && (flags & type)) { + r = !!test_bit(index - start, bitmap); + break; + } + } + + mutex_unlock(&kvm->lock); + + return r; +} + /* * Write @data into the MSR specified by @index. Select MSR specific fault * checks are bypassed if @host_initiated is %true. @@ -1483,6 +1515,9 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data, { struct msr_data msr; + if (!host_initiated && !kvm_msr_allowed(vcpu, index, KVM_MSR_ALLOW_WRITE)) + return -ENOENT; + switch (index) { case MSR_FS_BASE: case MSR_GS_BASE: @@ -1528,6 +1563,9 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data, struct msr_data msr; int ret; + if (!host_initiated && !kvm_msr_allowed(vcpu, index, KVM_MSR_ALLOW_READ)) + return -ENOENT; + msr.index = index; msr.host_initiated = host_initiated; @@ -3550,6 +3588,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_EXCEPTION_PAYLOAD: case KVM_CAP_SET_GUEST_DEBUG: case KVM_CAP_X86_USER_SPACE_MSR: + case KVM_CAP_X86_MSR_ALLOWLIST: r = 1; break; case KVM_CAP_SYNC_REGS: @@ -5075,6 +5114,110 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, return r; } +static bool msr_range_overlaps(struct kvm *kvm, struct msr_bitmap_range *range) +{ + struct msr_bitmap_range *ranges = kvm->arch.msr_allowlist_ranges; + u32 i, count = kvm->arch.msr_allowlist_ranges_count; + bool r = false; + + for (i = 0; i < count; i++) { + u32 start = max(range->base, ranges[i].base); + u32 end = min(range->base + range->nmsrs, + ranges[i].base + ranges[i].nmsrs); + + if ((start < end) && (range->flags & ranges[i].flags)) { + r = true; + break; + } + } + + return r; +} + +static int kvm_vm_ioctl_add_msr_allowlist(struct kvm *kvm, void __user *argp) +{ + struct msr_bitmap_range *ranges = kvm->arch.msr_allowlist_ranges; + struct kvm_msr_allowlist __user *user_msr_allowlist = argp; + struct msr_bitmap_range range; + struct kvm_msr_allowlist kernel_msr_allowlist; + unsigned long *bitmap = NULL; + size_t bitmap_size; + int r = 0; + + if (copy_from_user(&kernel_msr_allowlist, user_msr_allowlist, + sizeof(kernel_msr_allowlist))) { + r = -EFAULT; + goto out; + } + + bitmap_size = BITS_TO_LONGS(kernel_msr_allowlist.nmsrs) * sizeof(long); + if (bitmap_size > KVM_MSR_ALLOWLIST_MAX_LEN) { + r = -EINVAL; + goto out; + } + + bitmap = memdup_user(user_msr_allowlist->bitmap, bitmap_size); + if (IS_ERR(bitmap)) { + r = PTR_ERR(bitmap); + goto out; + } + + range = (struct msr_bitmap_range) { + .flags = kernel_msr_allowlist.flags, + .base = kernel_msr_allowlist.base, + .nmsrs = kernel_msr_allowlist.nmsrs, + .bitmap = bitmap, + }; + + if (range.flags & ~(KVM_MSR_ALLOW_READ | KVM_MSR_ALLOW_WRITE)) { + r = -EINVAL; + goto out; + } + + /* + * Protect from concurrent calls to this function that could trigger + * a TOCTOU violation on kvm->arch.msr_allowlist_ranges_count. + */ + mutex_lock(&kvm->lock); + + if (kvm->arch.msr_allowlist_ranges_count >= + ARRAY_SIZE(kvm->arch.msr_allowlist_ranges)) { + r = -E2BIG; + goto out_locked; + } + + if (msr_range_overlaps(kvm, &range)) { + r = -EINVAL; + goto out_locked; + } + + /* Everything ok, add this range identifier to our global pool */ + ranges[kvm->arch.msr_allowlist_ranges_count++] = range; + +out_locked: + mutex_unlock(&kvm->lock); +out: + if (r) + kfree(bitmap); + + return r; +} + +static int kvm_vm_ioctl_clear_msr_allowlist(struct kvm *kvm) +{ + int i; + + mutex_lock(&kvm->lock); + + for (i = 0; i < kvm->arch.msr_allowlist_ranges_count; i++) + kfree(kvm->arch.msr_allowlist_ranges[i].bitmap); + kvm->arch.msr_allowlist_ranges_count = 0; + + mutex_unlock(&kvm->lock); + + return 0; +} + long kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { @@ -5381,6 +5524,12 @@ long kvm_arch_vm_ioctl(struct file *filp, case KVM_SET_PMU_EVENT_FILTER: r = kvm_vm_ioctl_set_pmu_event_filter(kvm, argp); break; + case KVM_X86_ADD_MSR_ALLOWLIST: + r = kvm_vm_ioctl_add_msr_allowlist(kvm, argp); + break; + case KVM_X86_CLEAR_MSR_ALLOWLIST: + r = kvm_vm_ioctl_clear_msr_allowlist(kvm); + break; default: r = -ENOTTY; } @@ -10086,6 +10235,8 @@ void kvm_arch_pre_destroy_vm(struct kvm *kvm) void kvm_arch_destroy_vm(struct kvm *kvm) { + int i; + if (current->mm == kvm->mm) { /* * Free memory regions allocated on behalf of userspace, @@ -10102,6 +10253,8 @@ void kvm_arch_destroy_vm(struct kvm *kvm) } if (kvm_x86_ops.vm_destroy) kvm_x86_ops.vm_destroy(kvm); + for (i = 0; i < kvm->arch.msr_allowlist_ranges_count; i++) + kfree(kvm->arch.msr_allowlist_ranges[i].bitmap); kvm_pic_destroy(kvm); kvm_ioapic_destroy(kvm); kvm_free_vcpus(kvm); diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 13fc7de1eb50..4d6bb06e0fb1 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1041,6 +1041,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_HALT_POLL 182 #define KVM_CAP_ASYNC_PF_INT 183 #define KVM_CAP_X86_USER_SPACE_MSR 184 +#define KVM_CAP_X86_MSR_ALLOWLIST 185 #ifdef KVM_CAP_IRQ_ROUTING @@ -1542,6 +1543,10 @@ struct kvm_pv_cmd { /* Available with KVM_CAP_S390_PROTECTED */ #define KVM_S390_PV_COMMAND _IOWR(KVMIO, 0xc5, struct kvm_pv_cmd) +/* Available with KVM_CAP_X86_MSR_ALLOWLIST */ +#define KVM_X86_ADD_MSR_ALLOWLIST _IOW(KVMIO, 0xc6, struct kvm_msr_allowlist) +#define KVM_X86_CLEAR_MSR_ALLOWLIST _IO(KVMIO, 0xc7) + /* Secure Encrypted Virtualization command */ enum sev_cmd_id { /* Guest initialization commands */ From patchwork Mon Aug 3 21:14:23 2020 Content-Type: text/plain; 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Mon, 3 Aug 2020 21:14:44 +0000 Received: from u79c5a0a55de558.ant.amazon.com (10.43.161.145) by EX13D20UWC001.ant.amazon.com (10.43.162.244) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 Aug 2020 21:14:41 +0000 From: Alexander Graf To: Paolo Bonzini CC: Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , "Joerg Roedel" , KarimAllah Raslan , Aaron Lewis , , , Subject: [PATCH v4 3/3] KVM: selftests: Add test for user space MSR handling Date: Mon, 3 Aug 2020 23:14:23 +0200 Message-ID: <20200803211423.29398-4-graf@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200803211423.29398-1-graf@amazon.com> References: <20200803211423.29398-1-graf@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.161.145] X-ClientProxiedBy: EX13D36UWB001.ant.amazon.com (10.43.161.84) To EX13D20UWC001.ant.amazon.com (10.43.162.244) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Now that we have the ability to handle MSRs from user space and also to select which ones we do want to prevent in-kernel KVM code from handling, let's add a selftest to show case and verify the API. Signed-off-by: Alexander Graf --- v2 -> v3: - s/KVM_CAP_ADD_MSR_ALLOWLIST/KVM_CAP_X86_MSR_ALLOWLIST/g - Add test to clear whitelist - Adjust to reply-less API - Fix asserts - Actually trap on MSR_IA32_POWER_CTL writes --- tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/x86_64/user_msr_test.c | 221 ++++++++++++++++++ 2 files changed, 222 insertions(+) create mode 100644 tools/testing/selftests/kvm/x86_64/user_msr_test.c diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index 4a166588d99f..80d5c348354c 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -55,6 +55,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/vmx_set_nested_state_test TEST_GEN_PROGS_x86_64 += x86_64/vmx_tsc_adjust_test TEST_GEN_PROGS_x86_64 += x86_64/xss_msr_test TEST_GEN_PROGS_x86_64 += x86_64/debug_regs +TEST_GEN_PROGS_x86_64 += x86_64/user_msr_test TEST_GEN_PROGS_x86_64 += clear_dirty_log_test TEST_GEN_PROGS_x86_64 += demand_paging_test TEST_GEN_PROGS_x86_64 += dirty_log_test diff --git a/tools/testing/selftests/kvm/x86_64/user_msr_test.c b/tools/testing/selftests/kvm/x86_64/user_msr_test.c new file mode 100644 index 000000000000..7b149424690d --- /dev/null +++ b/tools/testing/selftests/kvm/x86_64/user_msr_test.c @@ -0,0 +1,221 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * tests for KVM_CAP_X86_USER_SPACE_MSR and KVM_X86_ADD_MSR_ALLOWLIST + * + * Copyright (C) 2020, Amazon Inc. + * + * This is a functional test to verify that we can deflect MSR events + * into user space. + */ +#define _GNU_SOURCE /* for program_invocation_short_name */ +#include +#include +#include +#include +#include + +#include "test_util.h" + +#include "kvm_util.h" +#include "processor.h" + +#define VCPU_ID 5 + +u32 msr_reads, msr_writes; + +struct range_desc { + struct kvm_msr_allowlist allow; + void (*populate)(struct kvm_msr_allowlist *range); +}; + +static void populate_c0000000_read(struct kvm_msr_allowlist *range) +{ + u8 *bitmap = range->bitmap; + u32 idx = MSR_SYSCALL_MASK & (KVM_MSR_ALLOWLIST_MAX_LEN - 1); + + bitmap[idx / 8] &= ~(1 << (idx % 8)); +} + +static void populate_00000000_write(struct kvm_msr_allowlist *range) +{ + u8 *bitmap = range->bitmap; + u32 idx = MSR_IA32_POWER_CTL & (KVM_MSR_ALLOWLIST_MAX_LEN - 1); + + bitmap[idx / 8] &= ~(1 << (idx % 8)); +} + +struct range_desc ranges[] = { + { + .allow = { + .flags = KVM_MSR_ALLOW_READ, + .base = 0x00000000, + .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE, + }, + }, { + .allow = { + .flags = KVM_MSR_ALLOW_WRITE, + .base = 0x00000000, + .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE, + }, + .populate = populate_00000000_write, + }, { + .allow = { + .flags = KVM_MSR_ALLOW_READ | KVM_MSR_ALLOW_WRITE, + .base = 0x40000000, + .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE, + }, + }, { + .allow = { + .flags = KVM_MSR_ALLOW_READ, + .base = 0xc0000000, + .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE, + }, + .populate = populate_c0000000_read, + }, { + .allow = { + .flags = KVM_MSR_ALLOW_WRITE, + .base = 0xc0000000, + .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE, + }, + }, +}; + +static void guest_msr_calls(bool trapped) +{ + /* This goes into the in-kernel emulation */ + wrmsr(MSR_SYSCALL_MASK, 0); + + if (trapped) { + /* This goes into user space emulation */ + GUEST_ASSERT(rdmsr(MSR_SYSCALL_MASK) == MSR_SYSCALL_MASK); + } else { + GUEST_ASSERT(rdmsr(MSR_SYSCALL_MASK) != MSR_SYSCALL_MASK); + } + + /* If trapped == true, this goes into user space emulation */ + wrmsr(MSR_IA32_POWER_CTL, 0x1234); + + /* This goes into the in-kernel emulation */ + rdmsr(MSR_IA32_POWER_CTL); +} + +static void guest_code(void) +{ + guest_msr_calls(true); + + /* + * Disable allow listing, so that the kernel + * handles everything in the next round + */ + GUEST_SYNC(0); + + guest_msr_calls(false); + + GUEST_DONE(); +} + +static int handle_ucall(struct kvm_vm *vm) +{ + struct ucall uc; + + switch (get_ucall(vm, VCPU_ID, &uc)) { + case UCALL_ABORT: + TEST_FAIL("Guest assertion not met"); + break; + case UCALL_SYNC: + vm_ioctl(vm, KVM_X86_CLEAR_MSR_ALLOWLIST, NULL); + break; + case UCALL_DONE: + return 1; + default: + TEST_FAIL("Unknown ucall %lu", uc.cmd); + } + + return 0; +} + +static void handle_rdmsr(struct kvm_run *run) +{ + run->msr.data = run->msr.index; + msr_reads++; +} + +static void handle_wrmsr(struct kvm_run *run) +{ + /* ignore */ + msr_writes++; +} + +int main(int argc, char *argv[]) +{ + struct kvm_enable_cap cap = { + .cap = KVM_CAP_X86_USER_SPACE_MSR, + .args[0] = 1, + }; + struct kvm_vm *vm; + struct kvm_run *run; + int rc; + int i; + + /* Tell stdout not to buffer its content */ + setbuf(stdout, NULL); + + /* Create VM */ + vm = vm_create_default(VCPU_ID, 0, guest_code); + vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid()); + run = vcpu_state(vm, VCPU_ID); + + rc = kvm_check_cap(KVM_CAP_X86_USER_SPACE_MSR); + TEST_ASSERT(rc, "KVM_CAP_X86_USER_SPACE_MSR is available"); + vm_enable_cap(vm, &cap); + + rc = kvm_check_cap(KVM_CAP_X86_MSR_ALLOWLIST); + TEST_ASSERT(rc, "KVM_CAP_X86_MSR_ALLOWLIST is available"); + + /* Set up MSR allowlist */ + for (i = 0; i < ARRAY_SIZE(ranges); i++) { + struct kvm_msr_allowlist *a = &ranges[i].allow; + u32 bitmap_size = a->nmsrs / BITS_PER_BYTE; + struct kvm_msr_allowlist *range = malloc(sizeof(*a) + bitmap_size); + + TEST_ASSERT(range, "range alloc failed (%ld bytes)\n", sizeof(*a) + bitmap_size); + + *range = *a; + + /* Allow everything by default */ + memset(range->bitmap, 0xff, bitmap_size); + + if (ranges[i].populate) + ranges[i].populate(range); + + vm_ioctl(vm, KVM_X86_ADD_MSR_ALLOWLIST, range); + } + + while (1) { + rc = _vcpu_run(vm, VCPU_ID); + + TEST_ASSERT(rc == 0, "vcpu_run failed: %d\n", rc); + + switch (run->exit_reason) { + case KVM_EXIT_X86_RDMSR: + handle_rdmsr(run); + break; + case KVM_EXIT_X86_WRMSR: + handle_wrmsr(run); + break; + case KVM_EXIT_IO: + if (handle_ucall(vm)) + goto done; + break; + } + + } + +done: + TEST_ASSERT(msr_reads == 1, "Handled 1 rdmsr in user space"); + TEST_ASSERT(msr_writes == 1, "Handled 1 wrmsr in user space"); + + kvm_vm_free(vm); + + return 0; +}