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Message-ID: <eea8bf26-1c86-8e2b-9ded-cb0d09c08fcf@intel.com>
Date:   Fri, 15 Sep 2023 14:42:15 +0800
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Subject: Re: [PATCH v6 04/25] x86/fpu/xstate: Introduce kernel dynamic
 xfeature set
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To:     "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "Christopherson,, Sean" <seanjc@google.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     "peterz@infradead.org" <peterz@infradead.org>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        "Gao, Chao" <chao.gao@intel.com>,
        "john.allen@amd.com" <john.allen@amd.com>
References: <20230914063325.85503-1-weijiang.yang@intel.com>
 <20230914063325.85503-5-weijiang.yang@intel.com>
 <f16beeec3fba23a34c426f311239935c5be920ab.camel@intel.com>
From:   "Yang, Weijiang" <weijiang.yang@intel.com>
In-Reply-To: <f16beeec3fba23a34c426f311239935c5be920ab.camel@intel.com>
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On 9/15/2023 8:24 AM, Edgecombe, Rick P wrote:
> On Thu, 2023-09-14 at 02:33 -0400, Yang Weijiang wrote:
>> +static void __init init_kernel_dynamic_xfeatures(void)
>> +{
>> +       unsigned short cid;
>> +       int i;
>> +
>> +       for (i = 0; i < ARRAY_SIZE(xsave_kernel_dynamic_xfeatures);
>> i++) {
>> +               cid = xsave_kernel_dynamic_xfeatures[i];
>> +
>> +               if (cid && boot_cpu_has(cid))
>> +                       fpu_kernel_dynamic_xfeatures |= BIT_ULL(i);
>> +       }
>> +}
>> +
> I think this can be part of the max_features calculation that uses
> xsave_cpuid_features when you use use a fixed mask like Dave suggested
> in the other patch.

Yes, the max_features has already included CET supervisor state bit. After  use
fixed mask, this function is not needed.