[PATCH v7 32/33] x86/fred: disable FRED by default in its early stage

Xin Li
2023-04-04T10:56:56Z

Disable FRED by default in its early stage.

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 | 4 ++++
arch/x86/kernel/cpu/common.c | 3 +++
2 files changed, 7 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6221a1d057dd..c55ea60e1a0c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1498,6 +1498,10 @@
Warning: use of this parameter will taint the kernel
and may cause unknown problems.

+ fred
+ Forcefully enable flexible return and event delivery,
+ which is otherwise disabled by default.
+
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 eea41cb8722e..4db5e619fc97 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1467,6 +1467,9 @@ 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