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Message-ID: <5689dc7e-b0e0-1733-f00f-66dc7b62b960@intel.com>
Date:   Thu, 11 Nov 2021 11:28:04 +0800
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Subject: Re: [RFC PATCH v2 22/69] KVM: x86: Add vm_type to differentiate
 legacy VMs from protected VMs
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To:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Cc:     "Yamahata, Isaku" <isaku.yamahata@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        "erdemaktas@google.com" <erdemaktas@google.com>,
        Connor Kuehl <ckuehl@redhat.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>
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 <e2270f66-abd8-db17-c3bd-b6d9459624ec@redhat.com>
 <YO356ni0SjPsLsSo@google.com>
From:   Xiaoyao Li <xiaoyao.li@intel.com>
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On 7/14/2021 4:39 AM, Sean Christopherson wrote:
> On Tue, Jul 06, 2021, Paolo Bonzini wrote:
>> On 03/07/21 00:04, isaku.yamahata@intel.com wrote:
>>>    struct kvm_arch {
>>> +	unsigned long vm_type;
>>
>> Also why not just int or u8?
> 
> Heh, because kvm_dev_ioctl_create_vm() takes an "unsigned long" for the type and
> it felt wrong to store it as something else.  Storing it as a smaller field should
> be fine, I highly doubt we'll get to 256 types anytime soon :-)

It's the bit position. We can get only 8 types with u8 actually.

> 
> I think kvm_x86_ops.is_vm_type_supported() should take the full size though.
>