From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933603AbeBULlv (ORCPT ); Wed, 21 Feb 2018 06:41:51 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36670 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932556AbeBULlt (ORCPT ); Wed, 21 Feb 2018 06:41:49 -0500 Subject: Re: [PATCH v2 1/2] KVM: x86: Add a framework for supporting MSR-based features To: Tom Lendacky , x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Joerg Roedel , Borislav Petkov , Thomas Gleixner , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <20180215231156.31016.79657.stgit@tlendack-t1.amdoffice.net> <20180215231206.31016.78914.stgit@tlendack-t1.amdoffice.net> From: Paolo Bonzini Message-ID: <00583b68-d599-b709-133a-3741c258df13@redhat.com> Date: Wed, 21 Feb 2018 12:41:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180215231206.31016.78914.stgit@tlendack-t1.amdoffice.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/02/2018 00:12, Tom Lendacky wrote: > +static u32 msr_based_features[] = { > +}; > + > +static unsigned int num_msr_based_features = ARRAY_SIZE(msr_based_features); > + > bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer) > { > if (efer & efer_reserved_bits) > @@ -2785,6 +2794,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > case KVM_CAP_SET_BOOT_CPU_ID: > case KVM_CAP_SPLIT_IRQCHIP: > case KVM_CAP_IMMEDIATE_EXIT: > + case KVM_CAP_GET_MSR_FEATURES: > r = 1; > break; > case KVM_CAP_ADJUST_CLOCK: > @@ -4410,6 +4420,47 @@ long kvm_arch_vm_ioctl(struct file *filp, > r = kvm_x86_ops->mem_enc_unreg_region(kvm, ®ion); > break; > } > + case KVM_GET_MSR_INDEX_LIST: { > + struct kvm_msr_list __user *user_msr_list = argp; > + struct kvm_msr_list msr_list; > + unsigned int n; > + > + r = -EFAULT; > + if (copy_from_user(&msr_list, user_msr_list, sizeof(msr_list))) > + goto out; > + n = msr_list.nmsrs; > + msr_list.nmsrs = num_msr_based_features; > + if (copy_to_user(user_msr_list, &msr_list, sizeof(msr_list))) > + goto out; > + r = -E2BIG; > + if (n < msr_list.nmsrs) > + goto out; > + r = -EFAULT; > + if (copy_to_user(user_msr_list->indices, &msr_based_features, > + num_msr_based_features * sizeof(u32))) > + goto out; > + r = 0; > + break; I think it's better to have some logic in kvm_init_msr_list, to filter the MSR list based on whatever MSRs the backend provides. > + } > + case KVM_GET_MSR: { It's not that the API isn't usable, KVM_GET_MSR is fine for what we need here (it's not a fast path), but it's a bit confusing to have KVM_GET_MSR and KVM_GET_MSRS. I see two possibilities: 1) reuse KVM_GET_MSRS as in the previous version. It's okay to cut-and-paste code from msr_io. 2) find a name for KVM_GET_MSR that is better and different from KVM_GET_MSRS. KVM_GET_HOST_MSR or KVM_GET_HOST_FEATURE_MSR come to mind, but I'm obviously open to other suggestions. Thanks! Paolo > + struct kvm_msr_entry __user *user_msr = argp; > + struct kvm_msr_entry msr; > + > + r = -EFAULT; > + if (copy_from_user(&msr, user_msr, sizeof(msr))) > + goto out; > + > + r = 1; > + if (!kvm_x86_ops->msr_feature || kvm_x86_ops->msr_feature(&msr)) > + goto out; > + > + r = -EFAULT; > + if (copy_to_user(user_msr, &msr, sizeof(msr))) > + goto out; > + > + r = 0; > + break; > + }