linux-kernel - Re: [PATCH v2 2/5] x86/cpufeatures: Add Intel feature bits for Speculation Control

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-next>] [day] [month] [year] [list]

Date:   Tue, 23 Jan 2018 17:28:35 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Woodhouse, David" <dwmw@...zon.co.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tim.c.chen@...ux.intel.com" <tim.c.chen@...ux.intel.com>,
        "arjan@...ux.intel.com" <arjan@...ux.intel.com>,
        "Raslan, KarimAllah" <karahmed@...zon.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "gregkh@...ux-foundation.org" <gregkh@...ux-foundation.org>
Subject: Re: [PATCH v2 2/5] x86/cpufeatures: Add Intel feature bits for
 Speculation Control

On 01/23/2018 05:23 PM, Woodhouse, David wrote:
> On Tue, 2018-01-23 at 10:43 -0800, Dave Hansen wrote:
...
>>>   /* Intel-defined CPU features, CPUID level 0x00000007:0 (EDX), word 18 */
>>>   #define X86_FEATURE_AVX512_4VNNIW    (18*32+ 2) /* AVX-512 Neural Network Instructions */
>>>   #define X86_FEATURE_AVX512_4FMAPS    (18*32+ 3) /* AVX-512 Multiply Accumulation Single precision */
>>> +#define X86_FEATURE_SPEC_CTRL                (18*32+26) /* Speculation Control (IBRS + IBPB) */
>>> +#define X86_FEATURE_STIBP            (18*32+27) /* Single Thread Indirect Branch Predictors */
>>> +#define X86_FEATURE_ARCH_CAPABILITIES        (18*32+29) /* IA32_ARCH_CAPABILITIES MSR (Intel) */
>> Should we be adding flags (STIBP) for which we currently have no user in
>> the kernel?
> They're in an existing word (now) so it costs us absolutely nothing to
> do so. And they'll be exposed to KVM guests in imminent patches if
> nothing else.

Doesn't just defining it here generate something in the tables that then
get exported in /proc/cpuinfo?  That's far from our most strict ABI, but
a single #define here can be seen by users IIRC.