From 3810da12710aaa05c6101418675c923642a80c0c Mon Sep 17 00:00:00 2001 From: Xin Li Date: Tue, 5 Dec 2023 02:49:57 -0800 Subject: [PATCH] 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: Xin Li Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Tested-by: Shan Kang Link: https://lore.kernel.org/r/20231205105030.8698-9-xin3.li@intel.com --- .../admin-guide/kernel-parameters.txt | 6 +++++ arch/x86/kernel/traps.c | 26 +++++++++++++++++++ 2 files changed, 32 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 31b3a25680d08..d6ea4f42127cf 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -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 diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index c3b2f863acf0f..3c37489018256 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -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(); -- 2.30.2