> >Disable FRED by default in its early stage. > > > >To enable FRED, a new kernel command line option "fred" needs to be added. > > > >Signed-off-by: Xin Li <xin3.li@xxxxxxxxx> > >--- > > 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 42af9ca0127e..0bc76d926dd4 100644 > >--- a/Documentation/admin-guide/kernel-parameters.txt > >+++ b/Documentation/admin-guide/kernel-parameters.txt > >@@ -1506,6 +1506,10 @@ > > 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 > >5de68356fe62..1a160337ad41 100644 > >--- a/arch/x86/kernel/cpu/common.c > >+++ b/arch/x86/kernel/cpu/common.c > >@@ -1434,6 +1434,9 @@ 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 > > Specifically, the intent is to enable it by default once hardware is widely available. > This allows e.g. distros to compile in the support for opt-in field testing before > throwing the switch. > > The motivation for this comes from the SMAP experience where the code was > functional and correct when merged, but a change elsewhere in the kernel code > base broke it during the intervening period. Thanks for the clarification.
