Date: Fri, 12 Jan 2018 10:02:24 -0800
From: Andi Kleen <ak@linux.intel.com>
To: David Woodhouse <dwmw@amazon.co.uk>
Cc: Paul Turner <pjt@google.com>, LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linux-foundation.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Dave Hansen <dave.hansen@intel.com>, tglx@linutronix.de,
        Kees Cook <keescook@google.com>,
        Rik van Riel <riel@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Jiri Kosina <jikos@kernel.org>, gnomes@lxorguk.ukuu.org.uk,
        x86@kernel.org, thomas.lendacky@amd.com,
        Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH] x86/retpoline: Fill RSB on context switch for affected
 CPUs
Message-ID: <20180112180224.GP6718@tassilo.jf.intel.com>
References: <1515779365-9032-1-git-send-email-dwmw@amazon.co.uk>
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> +	if ((!boot_cpu_has(X86_FEATURE_PTI) &&
> +	     !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
> +		setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
> +		pr_info("Filling RSB on context switch\n");

We need to do more things for Skylake (like idle and interrupt fill
and possibly deep call cahin), so I don't think it makes sense to

- have an individual flag for each of these. It can be just a single
flag that enables all of this for Skylake

- print something for each of them. that will just be very noisy
without any useful benefit to the user.

-Andi