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From: Geert Uytterhoeven <>
To: Josh Poimboeuf <>,
	Thomas Gleixner <>,
	Ingo Molnar <>,
	Peter Zijlstra <>,
	Jiri Kosina <>,
	Greg Kroah-Hartman <>,
	Ben Hutchings <>
	Geert Uytterhoeven <>,
Subject: [PATCH] cpu/speculation: Warn on unsupported mitigations= parameter
Date: Thu, 16 May 2019 09:09:35 +0200
Message-ID: <> (raw)

Currently, if the user specifies an unsupported mitigation strategy on
the kernel command line, it will be ignored silently.  The code will
fall back to the default strategy, possibly leaving the system more
vulnerable than expected.

This may happen due to e.g. a simple typo, or, for a stable kernel
release, because not all mitigation strategies have been backported.

Inform the user by printing a message.

Fixes: 98af8452945c5565 ("cpu/speculation: Add 'mitigations=' cmdline option")
Signed-off-by: Geert Uytterhoeven <>
 kernel/cpu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f2ef10460698e9ec..8458fda00e6ddb88 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2339,6 +2339,9 @@ static int __init mitigations_parse_cmdline(char *arg)
 		cpu_mitigations = CPU_MITIGATIONS_AUTO;
 	else if (!strcmp(arg, "auto,nosmt"))
 		cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
+	else
+		pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
+			arg);
 	return 0;

             reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-16  7:09 Geert Uytterhoeven [this message]
2019-05-16  7:48 ` Jiri Kosina
2019-05-16  8:16   ` Ingo Molnar
2019-05-16 17:43 ` Josh Poimboeuf
2019-06-26 15:16 ` [tip:smp/urgent] " tip-bot for Geert Uytterhoeven

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