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@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
Changes since v7:
* Add a log message when FRED is enabled.
---
Documentation/admin-guide/kernel-parameters.txt | 4 ++++
arch/x86/kernel/cpu/common.c | 3 +++
arch/x86/kernel/fred.c | 3 +++
3 files changed, 10 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
diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c
index 8d6dda8c8e71..f4d48f4f06b4 100644
--- a/arch/x86/kernel/fred.c
+++ b/arch/x86/kernel/fred.c
@@ -11,6 +11,9 @@
*/
void cpu_init_fred_exceptions(void)
{
+ /* When FRED is enabled by default, this log message may not needed */
+ pr_info("Initialize FRED on CPU%d\n", smp_processor_id());
+
wrmsrl(MSR_IA32_FRED_CONFIG,
FRED_CONFIG_REDZONE | /* Reserve for CALL emulation */
FRED_CONFIG_INT_STKLVL(0) |
--
2.34.1
