linux-kernel - Re: [PATCH v2] KVM: X86: deprecate obsolete KVM_GET

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Message-ID: <9054db11e0c946eba998864aa0c40fa2@huawei.com>
Date:   Fri, 28 Feb 2020 01:36:07 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH v2] KVM: X86: deprecate obsolete KVM_GET_CPUID2 ioctl

Vitaly Kuznetsov <vkuznets@...hat.com> writes:
>linmiaohe <linmiaohe@...wei.com> writes:
>
>> From: Miaohe Lin <linmiaohe@...wei.com>
>> -		if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid)))
>> -			goto out;
>> -		r = 0;
>> +		r = -EINVAL;
>>  		break;
>>  	}
>
>Braces are not really needed not but all other cases in the switch have it so let's leave them here too.
>

That's what I think too. :)

>>
>>  	case KVM_GET_MSRS: {
>> +/* KVM_GET_CPUID2 is deprecated, should not be used. */
>
>"should not be used" pre-patch, post-patch we can say "Can only be used as a reliable source of -EINVAL" :-)

That's right.

>
>  #define KVM_GET_CPUID2            _IOWR(KVMIO, 0x91, struct kvm_cpuid2)
>  /* Available with KVM_CAP_VAPIC */
>  #define KVM_TPR_ACCESS_REPORTING  _IOWR(KVMIO, 0x92, struct 
> kvm_tpr_access_ctl)
>
>Surprisingly (or not), KVM_GET_CPUID2 is not even described in Documentation/virt/kvm/api.txt.
>

Maybe KVM_GET_CPUID2 is defined for integrity only.

>
>Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
>

Many thanks for your review!