[PATCH v10 10/38] x86/fred: Disable FRED by default in its early stage

[Xin Li <xin3.li@xxxxxxxxx>]

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

Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
 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