linux-kernel - Re: [PATCH v3 01/13] x86/retpoline: Add initial retpoline support

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Message-ID: <20180105224357.33qguyuir7r7rgw6@pd.tnic>
Date:   Fri, 5 Jan 2018 23:43:57 +0100
From:   Borislav Petkov <bp@...e.de>
To:     "Woodhouse, David" <dwmw@...zon.co.uk>
Cc:     "brgerst@...il.com" <brgerst@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "tim.c.chen@...ux.intel.com" <tim.c.chen@...ux.intel.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "riel@...hat.com" <riel@...hat.com>,
        "keescook@...gle.com" <keescook@...gle.com>,
        "gnomes@...rguk.ukuu.org.uk" <gnomes@...rguk.ukuu.org.uk>,
        "pjt@...gle.com" <pjt@...gle.com>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>,
        "luto@...capital.net" <luto@...capital.net>,
        "jikos@...nel.org" <jikos@...nel.org>,
        "gregkh@...ux-foundation.org" <gregkh@...ux-foundation.org>
Subject: Re: [PATCH v3 01/13] x86/retpoline: Add initial retpoline support

On Fri, Jan 05, 2018 at 10:16:54PM +0000, Woodhouse, David wrote:
> You'd still want a RETPOLINE_AMD flag to enable that lfence; it's not
> just K8.

I think you're forgetting that we set K8 on everything >= K8 on AMD. So
this:

+       if (c->x86_vendor == X86_VENDOR_AMD)
+               setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);

can just as well be dropped and X86_FEATURE_K8 used everywhere.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--