Commit 1e7857b28020 for kernel

commit 1e7857b28020ba57ca7fdafae7ac855ba326c697
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon Mar 31 14:19:55 2025 -0700

    x86: don't re-generate cpufeaturemasks.h so eagerly

    It turns out the code to generate the x86 cpufeaturemasks.h header was
    way too aggressive, and would re-generate it whenever the timestamp on
    the kernel config file changed.

    Now, the regular 'make *config' tools are fairly careful to not rewrite
    the kernel config file unless the contents change, but other usecases
    aren't that careful.

    Michael Kelley reports that 'make-kpkg' ends up doing "make syncconfig"
    multiple times in prepping to build, and will modify the config file in
    the process (and then modify it back, but by then the timestamps have
    changed).

    Jakub Kicinski reports that the netdev CI does something similar in how
    it generates the config file in multiple steps.

    In both cases, the config file timestamp updates then cause the
    cpufeaturemasks.h file to be regenerated, and that in turn then causes
    lots of unnecessary rebuilds due to all the normal dependencies.

    Fix it by using our 'filechk' infrastructure in the Makefile to generate
    the header file.  That will only write a new version of the file if the
    contents of the file have actually changed.

    Fixes: 841326332bcb ("x86/cpufeatures: Generate the <asm/cpufeaturemasks.h> header based on build config")
    Reported-by: Michael Kelley <mhklinux@outlook.com>
    Reported-by: Jakub Kicinski <kuba@kernel.org>
    Link: https://lore.kernel.org/all/SN6PR02MB415756D1829740F6E8AC11D1D4D82@SN6PR02MB4157.namprd02.prod.outlook.com/
    Link: https://lore.kernel.org/all/20250328162311.08134fa6@kernel.org/
    Cc: Peter Anvin <hpa@zytor.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 0fc7e8fd1a2e..27efe2dc2aa8 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -277,12 +277,11 @@ cpufeaturemasks.hdr := arch/x86/include/generated/asm/cpufeaturemasks.h
 cpufeaturemasks.awk := $(srctree)/arch/x86/tools/cpufeaturemasks.awk
 cpufeatures_hdr := $(srctree)/arch/x86/include/asm/cpufeatures.h
 targets += $(cpufeaturemasks.hdr)
-quiet_cmd_gen_featuremasks = GEN     $@
-      cmd_gen_featuremasks = $(AWK) -f $(cpufeaturemasks.awk) $(cpufeatures_hdr) $(KCONFIG_CONFIG) > $@
+      filechk_gen_featuremasks = $(AWK) -f $(cpufeaturemasks.awk) $(cpufeatures_hdr) $(KCONFIG_CONFIG)

 $(cpufeaturemasks.hdr): $(cpufeaturemasks.awk) $(cpufeatures_hdr) $(KCONFIG_CONFIG) FORCE
 	$(shell mkdir -p $(dir $@))
-	$(call if_changed,gen_featuremasks)
+	$(call filechk,gen_featuremasks)
 archprepare: $(cpufeaturemasks.hdr)

 ###