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Message-ID: <7c3b4623-45ea-4340-ac47-334071c1d15f@amd.com>
Date: Mon, 3 Mar 2025 17:08:05 +0530
From: "Aithal, Srikanth" <sraithal@....com>
To: "Xin Li (Intel)" <xin@...or.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, will@...nel.org,
peterz@...radead.org, yury.norov@...il.com, akpm@...ux-foundation.org,
acme@...nel.org, namhyung@...nel.org, brgerst@...il.com,
andrew.cooper3@...rix.com, nik.borisov@...e.com
Subject: Re: [PATCH v6 3/5] x86/cpufeatures: Generate a feature mask header
based on build config
On 2/28/2025 1:53 PM, Xin Li (Intel) wrote:
> From: "H. Peter Anvin (Intel)" <hpa@...or.com>
>
> Introduce an AWK script to auto-generate a header with required and
> disabled feature masks based on <asm/cpufeatures.h> and current build
> config. Thus for any CPU feature with a build config, e.g., X86_FRED,
> simply add
>
> config X86_DISABLED_FEATURE_FRED
> def_bool y
> depends on !X86_FRED
>
> to arch/x86/Kconfig.cpufeatures, instead of adding a conditional CPU
> feature disable flag, e.g., DISABLE_FRED.
>
> Lastly the generated required and disabled feature masks will be added
> to their corresponding feature masks for this particular compile-time
> configuration.
>
> [ Xin: build integration improvements ]
>
> Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
> Signed-off-by: Xin Li (Intel) <xin@...or.com>
> Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>
> ---
>
> Change in v6:
> * Make the AWK script work for mawk and BusyBox awk (Borislav Petkov).
>
> Change in v5:
> * More polishes (Nikolay Borisov).
>
> Changes in v4:
> * Add a few high-level comments to the AWK script (Nikolay Borisov).
> * Enforce CPU feature mask values to be unsigned.
>
> Changes in v3:
> * Remove AWK code that generates extra debugging comments (Brian Gerst).
> * Move SSE_MASK to verify_cpu.S, the only place it is used (Brian Gerst).
>
> Change in v2:
> * Remove code generating unused macros {REQUIRED,DISABLED}_FEATURE(x)
> to tell if a CPU feature, e.g., X86_FEATURE_FRED, is a required or
> disabled feature for this particular compile-time configuration.
> ---
> arch/x86/Makefile | 17 ++++++-
> arch/x86/boot/cpucheck.c | 3 +-
> arch/x86/boot/cpuflags.c | 1 -
> arch/x86/boot/mkcpustr.c | 3 +-
> arch/x86/include/asm/Kbuild | 1 +
> arch/x86/include/asm/cpufeature.h | 1 +
> arch/x86/include/asm/cpufeatures.h | 8 ---
> arch/x86/kernel/verify_cpu.S | 4 ++
> arch/x86/tools/featuremasks.awk | 81 ++++++++++++++++++++++++++++++
> 9 files changed, 105 insertions(+), 14 deletions(-)
> create mode 100755 arch/x86/tools/featuremasks.awk
>
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 6784129328f6..60583987d320 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -263,9 +263,22 @@ archscripts: scripts_basic
> $(Q)$(MAKE) $(build)=arch/x86/tools relocs
>
> ###
> -# Syscall table generation
> +# Feature masks header and syscall table generation
>
> -archheaders:
> +out := arch/x86/include/generated/asm
> +featuremasks_hdr := featuremasks.h
> +featuremasks_awk := $(srctree)/arch/x86/tools/featuremasks.awk
> +cpufeatures_hdr := $(srctree)/arch/x86/include/asm/cpufeatures.h
> +quiet_cmd_gen_featuremasks = GEN $@
> + cmd_gen_featuremasks = $(AWK) -f $(featuremasks_awk) $(cpufeatures_hdr) $(KCONFIG_CONFIG) > $@
> +
> +$(out)/$(featuremasks_hdr): $(featuremasks_awk) $(cpufeatures_hdr) $(KCONFIG_CONFIG) FORCE
> + $(shell mkdir -p $(out))
> + $(call if_changed,gen_featuremasks)
> +
> +targets += $(out)/$(featuremasks_hdr)
> +
> +archheaders: $(out)/$(featuremasks_hdr)
> $(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
>
> ###
> diff --git a/arch/x86/boot/cpucheck.c b/arch/x86/boot/cpucheck.c
> index 0aae4d4ed615..8d03a741d1b2 100644
> --- a/arch/x86/boot/cpucheck.c
> +++ b/arch/x86/boot/cpucheck.c
> @@ -22,10 +22,11 @@
> # include "boot.h"
> #endif
> #include <linux/types.h>
> +#include <asm/featuremasks.h>
> #include <asm/intel-family.h>
> #include <asm/processor-flags.h>
> -#include <asm/required-features.h>
> #include <asm/msr-index.h>
> +
> #include "string.h"
> #include "msr.h"
>
> diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c
> index d75237ba7ce9..0cabdacb2a2f 100644
> --- a/arch/x86/boot/cpuflags.c
> +++ b/arch/x86/boot/cpuflags.c
> @@ -3,7 +3,6 @@
> #include "bitops.h"
>
> #include <asm/processor-flags.h>
> -#include <asm/required-features.h>
> #include <asm/msr-index.h>
> #include "cpuflags.h"
>
> diff --git a/arch/x86/boot/mkcpustr.c b/arch/x86/boot/mkcpustr.c
> index da0ccc5de538..b90110109675 100644
> --- a/arch/x86/boot/mkcpustr.c
> +++ b/arch/x86/boot/mkcpustr.c
> @@ -12,8 +12,6 @@
>
> #include <stdio.h>
>
> -#include "../include/asm/required-features.h"
> -#include "../include/asm/disabled-features.h"
> #include "../include/asm/cpufeatures.h"
> #include "../include/asm/vmxfeatures.h"
> #include "../kernel/cpu/capflags.c"
> @@ -23,6 +21,7 @@ int main(void)
> int i, j;
> const char *str;
>
> + printf("#include <asm/featuremasks.h>\n\n");
> printf("static const char x86_cap_strs[] =\n");
>
> for (i = 0; i < NCAPINTS; i++) {
> diff --git a/arch/x86/include/asm/Kbuild b/arch/x86/include/asm/Kbuild
> index 58f4ddecc5fa..51022d21003e 100644
> --- a/arch/x86/include/asm/Kbuild
> +++ b/arch/x86/include/asm/Kbuild
> @@ -8,6 +8,7 @@ generated-y += syscalls_x32.h
> generated-y += unistd_32_ia32.h
> generated-y += unistd_64_x32.h
> generated-y += xen-hypercalls.h
> +generated-y += featuremasks.h
>
> generic-y += early_ioremap.h
> generic-y += fprobe.h
> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> index de1ad09fe8d7..077a5bbd1cc5 100644
> --- a/arch/x86/include/asm/cpufeature.h
> +++ b/arch/x86/include/asm/cpufeature.h
> @@ -9,6 +9,7 @@
> #include <asm/asm.h>
> #include <linux/bitops.h>
> #include <asm/alternative.h>
> +#include <asm/featuremasks.h>
>
> enum cpuid_leafs
> {
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index c8701abb7752..b9b7329f4ac4 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -2,14 +2,6 @@
> #ifndef _ASM_X86_CPUFEATURES_H
> #define _ASM_X86_CPUFEATURES_H
>
> -#ifndef _ASM_X86_REQUIRED_FEATURES_H
> -#include <asm/required-features.h>
> -#endif
> -
> -#ifndef _ASM_X86_DISABLED_FEATURES_H
> -#include <asm/disabled-features.h>
> -#endif
> -
> /*
> * Defines x86 CPU feature bits
> */
> diff --git a/arch/x86/kernel/verify_cpu.S b/arch/x86/kernel/verify_cpu.S
> index 1258a5872d12..a23a65d5d177 100644
> --- a/arch/x86/kernel/verify_cpu.S
> +++ b/arch/x86/kernel/verify_cpu.S
> @@ -29,8 +29,12 @@
> */
>
> #include <asm/cpufeatures.h>
> +#include <asm/featuremasks.h>
> #include <asm/msr-index.h>
>
> +#define SSE_MASK \
> + (REQUIRED_MASK0 & ((1<<(X86_FEATURE_XMM & 31)) | (1<<(X86_FEATURE_XMM2 & 31))))
> +
> SYM_FUNC_START_LOCAL(verify_cpu)
> pushf # Save caller passed flags
> push $0 # Kill any dangerous flags
> diff --git a/arch/x86/tools/featuremasks.awk b/arch/x86/tools/featuremasks.awk
> new file mode 100755
> index 000000000000..fd3e72147157
> --- /dev/null
> +++ b/arch/x86/tools/featuremasks.awk
> @@ -0,0 +1,81 @@
> +#!/usr/bin/awk
> +#
> +# Convert cpufeatures.h to a list of compile-time masks
> +# Note: this blithly assumes that each word has at least one
> +# feature defined in it; if not, something else is wrong!
> +#
> +
> +BEGIN {
> + printf "#ifndef _ASM_X86_FEATUREMASKS_H\n";
> + printf "#define _ASM_X86_FEATUREMASKS_H\n\n";
> +
> + file = 0
> +}
> +
> +FNR == 1 {
> + ++file;
> +
> + # arch/x86/include/asm/cpufeatures.h
> + if (file == 1)
> + FS = "[ \t()*+]+";
> +
> + # .config
> + if (file == 2)
> + FS = "=";
> +}
> +
> +# Create a dictionary of sorts, containing all defined feature bits
> +file == 1 && $1 ~ /^#define$/ && $2 ~ /^X86_FEATURE_/ {
> + nfeat = $3 * $4 + $5;
> + feat = $2;
> + sub(/^X86_FEATURE_/, "", feat);
> + feats[nfeat] = feat;
> +}
> +file == 1 && $1 ~ /^#define$/ && $2 == "NCAPINTS" {
> + ncapints = int($3);
> +}
> +
> +# Create a dictionary featstat[REQUIRED|DISABLED, FEATURE_NAME] = on | off
> +file == 2 && $1 ~ /^CONFIG_X86_(REQUIRED|DISABLED)_FEATURE_/ {
> + on = ($2 == "y");
> + if (split($1, fs, "CONFIG_X86_|_FEATURE_") == 3)
> + featstat[fs[2], fs[3]] = on;
> +}
> +
> +END {
> + sets[1] = "REQUIRED";
> + sets[2] = "DISABLED";
> +
> + for (ns in sets) {
> + s = sets[ns];
> +
> + printf "/*\n";
> + printf " * %s features:\n", s;
> + printf " *\n";
> + fstr = "";
> + for (i = 0; i < ncapints; i++) {
> + mask = 0;
> + for (j = 0; j < 32; j++) {
> + feat = feats[i*32 + j];
> + if (featstat[s, feat]) {
> + nfstr = fstr " " feat;
> + if (length(nfstr) > 72) {
> + printf " * %s\n", fstr;
> + nfstr = " " feat;
> + }
> + fstr = nfstr;
> + mask += (2 ^ j);
> + }
> + }
> + masks[i] = mask;
> + }
> + printf " * %s\n */\n", fstr;
> +
> + for (i = 0; i < ncapints; i++)
> + printf "#define %s_MASK%d\t0x%08xU\n", s, i, masks[i];
> +
> + printf "#define %s_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != %d)\n\n", s, ncapints;
> + }
> +
> + printf "#endif /* _ASM_X86_FEATUREMASKS_H */\n";
> +}
Building kselftests is regressing with this commit on next-20250303.
# make headers
HOSTCC scripts/basic/fixdep
HOSTCC scripts/unifdef
WRAP arch/x86/include/generated/uapi/asm/bpf_perf_event.h
WRAP arch/x86/include/generated/uapi/asm/errno.h
WRAP arch/x86/include/generated/uapi/asm/fcntl.h
WRAP arch/x86/include/generated/uapi/asm/ioctl.h
WRAP arch/x86/include/generated/uapi/asm/ioctls.h
WRAP arch/x86/include/generated/uapi/asm/ipcbuf.h
WRAP arch/x86/include/generated/uapi/asm/param.h
WRAP arch/x86/include/generated/uapi/asm/poll.h
WRAP arch/x86/include/generated/uapi/asm/resource.h
WRAP arch/x86/include/generated/uapi/asm/socket.h
WRAP arch/x86/include/generated/uapi/asm/sockios.h
WRAP arch/x86/include/generated/uapi/asm/termbits.h
WRAP arch/x86/include/generated/uapi/asm/termios.h
WRAP arch/x86/include/generated/uapi/asm/types.h
make[1]: *** No rule to make target '.config', needed by
'arch/x86/include/generated/asm/featuremasks.h'. Stop.
make: *** [Makefile:251: __sub-make] Error 2
The same used to work fine until next-20250228.
Recreation steps:
1. Clone next-20250303
2. make distclean
3. make headers
Srikanth Aithal <sraithal@....com>
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