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Message-ID: <20230703103255.GE4253@hirez.programming.kicks-ass.net>
Date: Mon, 3 Jul 2023 12:32:55 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Waiman Long <longman@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
Jacob Pan <jacob.jun.pan@...ux.intel.com>,
Len Brown <lenb@...nel.org>, Jonathan Corbet <corbet@....net>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
x86@...nel.org, linux-pm@...r.kernel.org,
Robin Jarry <rjarry@...hat.com>, Joe Mario <jmario@...hat.com>
Subject: Re: [PATCH v4 4/4] intel_idle: Add ibrs_off module parameter to
force disable IBRS
On Tue, Jun 27, 2023 at 10:25:54PM -0400, Waiman Long wrote:
> @@ -69,6 +69,7 @@ static int max_cstate = CPUIDLE_STATE_MAX - 1;
> static unsigned int disabled_states_mask __read_mostly;
> static unsigned int preferred_states_mask __read_mostly;
> static bool force_irq_on __read_mostly;
> +static bool ibrs_off __read_mostly;
>
> static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
>
> @@ -1919,12 +1920,15 @@ static void state_update_enter_method(struct cpuidle_state *state, int cstate)
> }
>
> if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS) &&
> - state->flags & CPUIDLE_FLAG_IBRS) {
> + ((state->flags & CPUIDLE_FLAG_IBRS) || ibrs_off)) {
> /*
> * IBRS mitigation requires that C-states are entered
> * with interrupts disabled.
> */
> - WARN_ON_ONCE(state->flags & CPUIDLE_FLAG_IRQ_ENABLE);
> + if (ibrs_off && (state->flags & CPUIDLE_FLAG_IRQ_ENABLE))
> + state->flags &= ~CPUIDLE_FLAG_IRQ_ENABLE;
> + else
> + WARN_ON_ONCE(state->flags & CPUIDLE_FLAG_IRQ_ENABLE);
If you're respinning this, you can leave out the else and avoid the
indent on the WARN:
+ if (ibrs_off && (state->flags & CPUIDLE_FLAG_IRQ_ENABLE))
+ state->flags &= ~CPUIDLE_FLAG_IRQ_ENABLE;
WARN_ON_ONCE(state->flags & CPUIDLE_FLAG_IRQ_ENABLE);
Same effect, simpler code and all that.
> state->enter = intel_idle_ibrs;
> return;
> }
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