Commit 3810da12 authored by Xin Li's avatar Xin Li Committed by Borislav Petkov (AMD)
Browse files

x86/fred: Add a fred= cmdline param 



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: default avatarXin Li <xin3.li@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Tested-by: default avatarShan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-9-xin3.li@intel.com
parent e554a8ca

Documentation/admin-guide/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/traps.c

+26 −0
Original line number Diff line number Diff line
@@ -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();