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From:   Xin Li <xin3.li@intel.com>
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Subject: [PATCH v10 10/38] x86/fred: Disable FRED by default in its early stage
Date:   Wed, 13 Sep 2023 21:47:37 -0700
Message-Id: <20230914044805.301390-11-xin3.li@intel.com>
In-Reply-To: <20230914044805.301390-1-xin3.li@intel.com>
References: <20230914044805.301390-1-xin3.li@intel.com>
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To enable FRED, a new kernel command line option "fred" needs to be added.

Tested-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <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 0a1731a0f0ef..42def5cc7552 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1525,6 +1525,9 @@
 			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 382d4e6b848d..317b4877e9c7 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1486,6 +1486,9 @@ 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
-- 
2.34.1