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x86/fred: Enable FRED by default

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When FRED was added to the mainline kernel, it was set up as an explicit
opt-in due to the risk of regressions before hardware was available publicly.

Now, Panther Lake (Core Ultra 300 series) has been released, and benchmarking
by Phoronix has shown that it provides a significant performance benefit on
most workloads:

  https://www.phoronix.com/review/intel-fred-panther-lake

Accordingly, enable FRED by default if the CPU supports it. FRED can of
course still be disabled via the fred=off command line option.

Touch up Kconfig help too.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://patch.msgid.link/20260325230151.1898287-2-hpa@zytor.com
This commit is contained in:
H. Peter Anvin
2026-03-25 16:01:47 -07:00
committed by Borislav Petkov (AMD)
parent c369299895
commit ac66a73be0
3 changed files with 4 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -1750,8 +1750,8 @@ Kernel parameters
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.
on: enable FRED when it's present, the default setting.
off: disable FRED.
ftrace=[tracer]
[FTRACE] will set and start the specified tracer

2
arch/x86/Kconfig
View File

@@ -557,7 +557,7 @@ config X86_FRED
bool "Flexible Return and Event Delivery"
depends on X86_64
help
When enabled, try to use Flexible Return and Event Delivery
When enabled, use Flexible Return and Event Delivery
instead of the legacy SYSCALL/SYSENTER/IDT architecture for
ring transitions and exception/interrupt handling if the
system supports it.

2
arch/x86/kernel/cpu/common.c
View File

@@ -1746,7 +1746,7 @@ static void __init cpu_parse_early_param(void)
/* Minimize the gap between FRED is available and available but disabled. */
arglen = cmdline_find_option(boot_command_line, "fred", arg, sizeof(arg));
if (arglen != 2 || strncmp(arg, "on", 2))
if (arglen == 3 && !strncmp(arg, "off", 3))
setup_clear_cpu_cap(X86_FEATURE_FRED);
arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg));