linux-kernel - Re: [PATCH v6 04/25] x86/fpu/xstate: Introduce kernel dynamic xfeature set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <eea8bf26-1c86-8e2b-9ded-cb0d09c08fcf@intel.com>
Date:   Fri, 15 Sep 2023 14:42:15 +0800
From:   "Yang, Weijiang" <weijiang.yang@...el.com>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "peterz@...radead.org" <peterz@...radead.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "john.allen@....com" <john.allen@....com>
Subject: Re: [PATCH v6 04/25] x86/fpu/xstate: Introduce kernel dynamic
 xfeature set

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.