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From: Dominik Brodowski <law@dominikbrodowski.net>
To: Andi Kleen <andi@firstfloor.org>
Cc: tglx@linutronix.de, x86@kernel.org, dwmw@amazon.co.uk,
	linux-kernel@vger.kernel.org, pjt@google.com,
	torvalds@linux-foundation.org, gregkh@linux-foundation.org,
	peterz@infradead.org, luto@amacapital.net,
	thomas.lendacky@amd.com, arjan.van.de.ven@intel.com,
	Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 1/4] x86/retpoline: Add new mode RETPOLINE_UNDERFLOW
Date: Fri, 12 Jan 2018 23:13:13 +0100	[thread overview]
Message-ID: <20180112221313.GA13035@light.dominikbrodowski.net> (raw)
In-Reply-To: <20180112184550.6573-2-andi@firstfloor.org>

> @@ -209,6 +234,11 @@ static void __init spectre_v2_select_mitigation(void)
>  		mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC :
>  					 SPECTRE_V2_RETPOLINE_MINIMAL;
>  		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
> +		if (mode == SPECTRE_V2_RETPOLINE_GENERIC &&
> +			cpu_needs_underflow_protection()) {
> +			mode = SPECTRE_V2_RETPOLINE_UNDERFLOW;
> +			setup_force_cpu_cap(X86_FEATURE_RETURN_UNDERFLOW);
> +		}
>  	}

Why does this require a retp-compatible compiler to be enabled?

Thanks,
	Dominik

  reply	other threads:[~2018-01-12 22:27 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-12 18:45 Improve retpoline for Skylake Andi Kleen
2018-01-12 18:45 ` [PATCH 1/4] x86/retpoline: Add new mode RETPOLINE_UNDERFLOW Andi Kleen
2018-01-12 22:13   ` Dominik Brodowski [this message]
2018-01-12 22:57     ` Andi Kleen
2018-01-12 18:45 ` [PATCH 2/4] x86/retpoline: Avoid return buffer underflows on context switch Andi Kleen
2018-01-12 18:45 ` [PATCH 3/4] x86/retpoline: Fill return buffer after idle Andi Kleen
2018-01-12 18:45 ` [PATCH 4/4] x86/retpoline: Fill return buffer on interrupt return to kernel Andi Kleen
2018-01-12 19:12 ` Improve retpoline for Skylake David Woodhouse
2018-01-12 19:21   ` Andi Kleen
2018-01-12 22:03     ` Henrique de Moraes Holschuh
2018-01-15  8:26       ` Jon Masters
2018-01-15  9:06         ` David Woodhouse
2018-01-15 10:03         ` Thomas Gleixner
2018-01-15 10:20           ` David Woodhouse
2018-01-15 16:57         ` Andy Lutomirski
2018-01-15 17:38           ` Andrew Cooper
2018-01-15 17:56             ` Van De Ven, Arjan
2018-01-15 18:06             ` Andy Lutomirski
2018-01-15 18:07               ` David Woodhouse
2018-01-15 18:10                 ` Andy Lutomirski

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