* [PATCH 2/3] x86/numa: Add CPU_SUP_AMD dependency for legacy AMD NUMA
2026-10-31 7:51 [PATCH 0/3] x86: Make processor vendor selection available without EXPERT Vincent Mailhol
2026-10-31 7:51 ` [PATCH 1/3] x86/mce: Add CPU_SUP_* dependencies for Intel/Zhaoxin MCE features Vincent Mailhol
@ 2026-10-31 7:51 ` Vincent Mailhol
2026-10-31 7:51 ` [PATCH 3/3] x86/cpu: don't gate PROCESSOR_SELECT with EXPERT Vincent Mailhol
2 siblings, 0 replies; 5+ messages in thread
From: Vincent Mailhol @ 2026-10-31 7:51 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin
Cc: linux-kernel, Vincent Mailhol
The legacy AMD NUMA probe reads topology from an Opteron northbridge.
It is only useful when AMD CPUs are supported, so gate it with
CPU_SUP_AMD.
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
---
arch/x86/Kconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e09ec15a689a..6ee0265b5483 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1524,7 +1524,7 @@ config NUMA
config AMD_NUMA
def_bool y
prompt "Old style AMD Opteron NUMA detection"
- depends on X86_64 && NUMA && PCI
+ depends on X86_64 && NUMA && PCI && CPU_SUP_AMD
help
Enable AMD NUMA node topology detection. You should say Y here if
you have a multi processor AMD system. This uses an old method to
--
2.56.0
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 3/3] x86/cpu: don't gate PROCESSOR_SELECT with EXPERT
2026-10-31 7:51 [PATCH 0/3] x86: Make processor vendor selection available without EXPERT Vincent Mailhol
2026-10-31 7:51 ` [PATCH 1/3] x86/mce: Add CPU_SUP_* dependencies for Intel/Zhaoxin MCE features Vincent Mailhol
2026-10-31 7:51 ` [PATCH 2/3] x86/numa: Add CPU_SUP_AMD dependency for legacy AMD NUMA Vincent Mailhol
@ 2026-10-31 7:51 ` Vincent Mailhol
2026-10-31 13:58 ` Dave Hansen
2 siblings, 1 reply; 5+ messages in thread
From: Vincent Mailhol @ 2026-10-31 7:51 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin
Cc: linux-kernel, Vincent Mailhol
When doing a make oldconfig, the user might get asked questions about
processor vendors. When the goal is to build a kernel for a specific
machine, those questions are irrelevant.
PROCESSOR_SELECT is a nice candidate to configure the CPU vendors once
and for all, but that feature is gated by EXPERT. It is unclear why this
menu should be hidden from the normal users. In comparison with the
other EXPERT features, knowing your CPU vendor does not require advanced
knowledge. After all, most machines even have a sticker on them to
remind you what is "inside".
Remove the EXPERT dependency from PROCESSOR_SELECT. Make the option N by
default so that all x86 CPU types remain supported by default.
This preserves the current default but now makes it easy to opt out when
configuring for a specific machine.
Finally, rephrase the menu guidance to make the description clearer:
- Change the PROCESSOR_SELECT entry text from "Supported processor
vendors" to "Customize supported processor vendors" to better
describe what the option does.
- Add a paragraph to PROCESSOR_SELECT help text to clarify that N is a
safe default.
- For each of the CPU_SUP_* entries, remove the "If unsure, say N"
sentence from the help text.
As a side benefit, this also allows users to more easily trim their
kernel without having to activate the EXPERT option or navigate many
submenus. This is illustrated in the measurements below done with gcc
15.3.0, which compare three builds: an x86_64 defconfig, that same
defconfig with only CONFIG_CPU_SUP_INTEL kept, then only
CONFIG_CPU_SUP_AMD kept and the other CONFIG_CPU_SUP_* deselected:
$ size vmlinux_{defconfig,intel_only,amd_only}.o
text data bss dec hex filename
29927107 4934948 752852 35614907 21f70bb vmlinux_defconfig.o
29819807 4919587 752340 35491734 21d8f96 vmlinux_intel_only.o
27452359 4252858 748692 32453909 1ef3515 vmlinux_amd_only.o
This shows a 0.35% reduction on an intel-only configuration and an 8.88%
reduction for an amd-only one.
The big difference in the amd-only build size is mostly explained by the
fact that CONFIG_MITIGATION_CALL_DEPTH_TRACKING gets automatically
disabled when removing CONFIG_CPU_SUP_INTEL.
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
---
arch/x86/Kconfig.cpu | 22 +++++-----------------
1 file changed, 5 insertions(+), 17 deletions(-)
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 6e7a366f0798..01eace1ea1f8 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -306,11 +306,15 @@ config X86_VMX_FEATURE_NAMES
depends on IA32_FEAT_CTL
menuconfig PROCESSOR_SELECT
- bool "Supported processor vendors" if EXPERT
+ default n
+ bool "Customize supported processor vendors"
help
This lets you choose what x86 vendor support code your kernel
will include.
+ To compile a kernel that can run on all supported x86 CPU types,
+ or if unsure, say N.
+
config CPU_SUP_INTEL
default y
bool "Support Intel processors" if PROCESSOR_SELECT
@@ -322,8 +326,6 @@ config CPU_SUP_INTEL
makes the kernel a tiny bit smaller. Disabling it on an Intel
CPU might render the kernel unbootable.
- If unsure, say N.
-
config CPU_SUP_CYRIX_32
default y
bool "Support Cyrix processors" if PROCESSOR_SELECT
@@ -336,8 +338,6 @@ config CPU_SUP_CYRIX_32
makes the kernel a tiny bit smaller. Disabling it on a Cyrix
CPU might render the kernel unbootable.
- If unsure, say N.
-
config CPU_SUP_AMD
default y
bool "Support AMD processors" if PROCESSOR_SELECT
@@ -349,8 +349,6 @@ config CPU_SUP_AMD
makes the kernel a tiny bit smaller. Disabling it on an AMD
CPU might render the kernel unbootable.
- If unsure, say N.
-
config CPU_SUP_HYGON
default y
bool "Support Hygon processors" if PROCESSOR_SELECT
@@ -363,8 +361,6 @@ config CPU_SUP_HYGON
makes the kernel a tiny bit smaller. Disabling it on an Hygon
CPU might render the kernel unbootable.
- If unsure, say N.
-
config CPU_SUP_CENTAUR
default y
bool "Support Centaur processors" if PROCESSOR_SELECT
@@ -376,8 +372,6 @@ config CPU_SUP_CENTAUR
makes the kernel a tiny bit smaller. Disabling it on a Centaur
CPU might render the kernel unbootable.
- If unsure, say N.
-
config CPU_SUP_TRANSMETA_32
default y
bool "Support Transmeta processors" if PROCESSOR_SELECT
@@ -390,8 +384,6 @@ config CPU_SUP_TRANSMETA_32
makes the kernel a tiny bit smaller. Disabling it on a Transmeta
CPU might render the kernel unbootable.
- If unsure, say N.
-
config CPU_SUP_ZHAOXIN
default y
bool "Support Zhaoxin processors" if PROCESSOR_SELECT
@@ -403,8 +395,6 @@ config CPU_SUP_ZHAOXIN
makes the kernel a tiny bit smaller. Disabling it on a Zhaoxin
CPU might render the kernel unbootable.
- If unsure, say N.
-
config CPU_SUP_VORTEX_32
default y
bool "Support Vortex processors" if PROCESSOR_SELECT
@@ -416,8 +406,6 @@ config CPU_SUP_VORTEX_32
Vortex CPU. Disabling this option on other types of CPUs
makes the kernel a tiny bit smaller.
- If unsure, say N.
-
config BROADCAST_TLB_FLUSH
def_bool y
depends on CPU_SUP_AMD && 64BIT
--
2.56.0
^ permalink raw reply [flat|nested] 5+ messages in thread