linux-kernel - [tip: x86/fred] x86/fred: Disable FRED by default in its early stage

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Date: Thu, 25 Jan 2024 18:21:35 -0000
From: "tip-bot2 for Xin Li" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Xin Li <xin3.li@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
 Shan Kang <shan.kang@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fred] x86/fred: Disable FRED by default in its early stage

The following commit has been merged into the x86/fred branch of tip:

Commit-ID:     7a1d75084df087dcae703d70a49274a3982e3681
Gitweb:        https://git.kernel.org/tip/7a1d75084df087dcae703d70a49274a3982e3681
Author:        Xin Li <xin3.li@...el.com>
AuthorDate:    Tue, 05 Dec 2023 02:49:57 -08:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 25 Jan 2024 19:10:30 +01:00

x86/fred: Disable FRED by default in its early stage

To enable FRED, a new kernel command line option "fred" needs to be added.

Signed-off-by: Xin Li <xin3.li@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Shan Kang <shan.kang@...el.com>
Link: https://lore.kernel.org/r/20231205105030.8698-9-xin3.li@intel.com

---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 arch/x86/kernel/cpu/common.c                    | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 31b3a25..c6c1a2c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1539,6 +1539,9 @@
 			Warning: use of this parameter will taint the kernel
 			and may cause unknown problems.
 
+	fred		[X86-64]
+			Enable flexible return and event delivery
+
 	ftrace=[tracer]
 			[FTRACE] will set and start the specified tracer
 			as early as possible in order to facilitate early
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0b97bcd..2121ec6 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1484,6 +1484,9 @@ static void __init cpu_parse_early_param(void)
 	char *argptr = arg, *opt;
 	int arglen, taint = 0;
 
+	if (!cmdline_find_option_bool(boot_command_line, "fred"))
+		setup_clear_cpu_cap(X86_FEATURE_FRED);
+
 #ifdef CONFIG_X86_32
 	if (cmdline_find_option_bool(boot_command_line, "no387"))
 #ifdef CONFIG_MATH_EMULATION