From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935950AbeBUQgc (ORCPT ); Wed, 21 Feb 2018 11:36:32 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50386 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932674AbeBUQga (ORCPT ); Wed, 21 Feb 2018 11:36:30 -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> <00583b68-d599-b709-133a-3741c258df13@redhat.com> <7f6a78ae-abab-2a03-aebd-e43e6fe168b4@amd.com> <94f6ed44-07ab-ff0f-2a6d-b3d8ff4ff4b1@redhat.com> From: Paolo Bonzini Message-ID: Date: Wed, 21 Feb 2018 17:36:27 +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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/02/2018 15:52, Tom Lendacky wrote: > On 2/21/2018 8:47 AM, Tom Lendacky wrote: >> On 2/21/2018 8:32 AM, Paolo Bonzini wrote: >>> On 21/02/2018 15:15, Tom Lendacky wrote: >>>> On 2/21/2018 5:41 AM, Paolo Bonzini wrote: >>>>> 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. >>>> >>>> Ok, that's what I had originally and then you said to just return the full >>>> list and let KVM_GET_MSR return a 0 or 1 if it was supported. I can switch >>>> it back. >>> >>> Hmm, I cannot find this remark (I would have been very confused, so I >>> tried to look for it). I commented on removing kvm_valid_msr_feature, >>> but not kvm_init_msr_list. >> >> I think this is the reply that sent me off on that track: >> https://marc.info/?l=linux-kernel&m=151862648123153&w=2 Yeah, it was referring to AMD hosts that don't have the MSR. Sorry for the confusion. >> I'll make it consistent with the other MSR-related items and initialize >> the list in kvm_init_msr_list(). I'll change the signature of the >> msr_feature() kvm_x86_ops callback to take an index and optionally return >> a data value so it can be used to check for support when building the >> list and return a value when needed. > > Hmm, actually I'll just leave the signature alone and pass in a local > kvm_msr_entry struct variable for the call when initializing the list. Sounds good! Paolo