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.
>
>> + }
>> + 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.
If I go back to trimming the list based on support, then KVM_GET_MSRS can
be used.
Thanks,
Tom
>
> 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;
>> + }
>
