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x86/fred: Add a fred= cmdline param

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Let command line option "fred" accept multiple options to make it
easier to tweak its behavior.

Currently, two options 'on' and 'off' are allowed, and the default
behavior is to disable FRED. To enable FRED, append "fred=on" to the
kernel command line.

  [ bp: Use cpu_feature_enabled(), touch ups. ]

Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-9-xin3.li@intel.com
This commit is contained in:
Xin Li 2023-12-05 02:49:57 -08:00 • committed by Borislav Petkov (AMD)
parent e554a8ca49
commit 3810da1271
2 changed files with 32 additions and 0 deletions
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6
Documentation/admin-guide/kernel-parameters.txt
View file

@ -1539,6 +1539,12 @@
Warning: use of this parameter will taint the kernel
and may cause unknown problems.
fred= [X86-64]
Enable/disable Flexible Return and Event Delivery.
Format: { on | off }
on: enable FRED when it's present.
off: disable FRED, the default setting.
ftrace=[tracer]
[FTRACE] will set and start the specified tracer
as early as possible in order to facilitate early

26
arch/x86/kernel/traps.c
View file

@ -1369,8 +1369,34 @@ DEFINE_IDTENTRY_SW(iret_error)
}
#endif
/* Do not enable FRED by default yet. */
static bool enable_fred __ro_after_init = false;
#ifdef CONFIG_X86_FRED
static int __init fred_setup(char *str)
{
if (!str)
return -EINVAL;
if (!cpu_feature_enabled(X86_FEATURE_FRED))
return 0;
if (!strcmp(str, "on"))
enable_fred = true;
else if (!strcmp(str, "off"))
enable_fred = false;
else
pr_warn("invalid FRED option: 'fred=%s'\n", str);
return 0;
}
early_param("fred", fred_setup);
#endif
void __init trap_init(void)
{
if (cpu_feature_enabled(X86_FEATURE_FRED) && !enable_fred)
setup_clear_cpu_cap(X86_FEATURE_FRED);
/* Init cpu_entry_area before IST entries are set up */
setup_cpu_entry_areas();