Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 10 Sep 2018 12:04:00 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Jiri Kosina <jikos@kernel.org>
cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        "Woodhouse, David" <dwmw@amazon.co.uk>,
        Andi Kleen <ak@linux.intel.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        "Schaufler, Casey" <casey.schaufler@intel.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v5 2/2] x86/speculation: Enable cross-hyperthread spectre
 v2 STIBP mitigation
In-Reply-To: <nycvar.YFH.7.76.1809101123520.15880@cbobk.fhfr.pm>
Message-ID: <alpine.DEB.2.21.1809101158080.1402@nanos.tec.linutronix.de>
References: <nycvar.YFH.7.76.1809101119280.15880@cbobk.fhfr.pm> <nycvar.YFH.7.76.1809101123520.15880@cbobk.fhfr.pm>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, 10 Sep 2018, Jiri Kosina wrote:
> +static void update_stibp_msr(void *info)
> +{
> +	wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
> +}
> +
> +void arch_smt_update(void)
> +{
> +	if (stibp_needed()) {

  	if (!stib_needed())
		return;

spares you an indentation level.

> +		u64 mask;

Newline between declarations and code please.

> +		mutex_lock(&spec_ctrl_mutex);
> +		mask = x86_spec_ctrl_base;
> +		if (cpu_smt_control == CPU_SMT_ENABLED)
> +			mask |= SPEC_CTRL_STIBP;
> +		else
> +			mask &= ~SPEC_CTRL_STIBP;
> +
> +		if (mask != x86_spec_ctrl_base) {
> +			pr_info("Spectre v2 cross-process SMT mitigation: %s STIBP\n",
> +					cpu_smt_control == CPU_SMT_ENABLED ?
> +						"Enabling" : "Disabling");
> +			x86_spec_ctrl_base = mask;
> +			on_each_cpu(update_stibp_msr, NULL, 1);
> +		}
> +		mutex_unlock(&spec_ctrl_mutex);
> +	}
> +}
> +

That looks much more palatable. One missing piece is the sysfs mitigation
file for spectre v2. That should reflect STIPB state as well.

Thanks,

	tglx