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[RESEND v1 2/3] x86/cpufeatures: Generate a feature mask header based on build config

Xin Li (Intel) posted 3 patches 1 year, 7 months ago
There is a newer version of this series
[RESEND v1 2/3] x86/cpufeatures: Generate a feature mask header based on build config
Posted by Xin Li (Intel) 1 year, 7 months ago 
From: "H. Peter Anvin (Intel)" <hpa@zytor.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.

Besides, the generated required and disabled feature masks will be
added to their corresponding CPU feature masks automatically.

[ Xin: build integration improvements ]

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
---
 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       |   1 +
 arch/x86/tools/featuremasks.awk    | 108 +++++++++++++++++++++++++++++
 9 files changed, 129 insertions(+), 14 deletions(-)
 create mode 100755 arch/x86/tools/featuremasks.awk

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 5ab93fcdd691..2a364fe0a5b4 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -241,9 +241,22 @@ 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 fed8d13ce252..49b982c4e932 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 a192bdea69e2..29c3481f40fc 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 += mcs_spinlock.h
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 0b9611da6c53..8332f596ba3c 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 3c7434329661..05503448b94d 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..3205cbb47b9c 100644
--- a/arch/x86/kernel/verify_cpu.S
+++ b/arch/x86/kernel/verify_cpu.S
@@ -29,6 +29,7 @@
  */
 
 #include <asm/cpufeatures.h>
+#include <asm/featuremasks.h>
 #include <asm/msr-index.h>
 
 SYM_FUNC_START_LOCAL(verify_cpu)
diff --git a/arch/x86/tools/featuremasks.awk b/arch/x86/tools/featuremasks.awk
new file mode 100755
index 000000000000..2af32c60fc76
--- /dev/null
+++ b/arch/x86/tools/featuremasks.awk
@@ -0,0 +1,108 @@
+#!/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
+}
+
+BEGINFILE {
+	switch (++file) {
+	case 1:			# cpufeatures.h
+		FPAT = "#[ \t]*[a-z]+|[A-Za-z0-9_]+|[^ \t]";
+		break;
+	case 2:			# .config
+		FPAT = "CONFIG_[A-Z0-9_]+|is not set|[yn]";
+		break;
+	}
+}
+
+file == 1 && $1 ~ /^#[ \t]*define$/ && $2 ~ /^X86_FEATURE_/ &&
+$3 == "(" && $5 == "*" && $7 == "+" && $9 == ")" {
+	nfeat = $4 * $6 + $8;
+	feat = $2;
+	sub(/^X86_FEATURE_/, "", feat);
+	feats[nfeat] = feat;
+}
+file == 1 && $1 ~ /^#[ \t]*define$/ && $2 == "NCAPINTS" {
+	ncapints = strtonum($3);
+}
+
+file == 2 && $1 ~ /^CONFIG_X86_[A-Z]*_FEATURE_/ {
+	on = ($2 == "y");
+	printf "/* %s = %s (%d) */\n", $1, $2, on;
+	if (split($1, fs, "CONFIG_X86_|_FEATURE_") == 3) {
+		printf "/* %s %s = %d */\n", fs[2], fs[3], on;
+		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++) {
+				nfeat = i*32 + j;
+				feat = feats[nfeat];
+				if (feat) {
+					st = !!featstat[s, feat];
+					if (st) {
+						nfstr = fstr " " feat;
+						if (length(nfstr) > 72) {
+							printf " *   %s\n", fstr;
+							nfstr = " " feat;
+						}
+						fstr = nfstr;
+					}
+					mask += st * (2 ^ j);
+				}
+			}
+			masks[i] = mask;
+		}
+		printf " *   %s\n */\n\n", fstr;
+
+		for (i = 0; i < ncapints; i++) {
+			printf "#define %s_MASK%-3d 0x%08x\n", s, i, masks[i];
+		}
+
+		printf "\n#define %s_MASKS ", s;
+		pfx = "{";
+		for (i = 0; i < ncapints; i++) {
+			printf "%s \\\n\t%s_MASK_%d", pfx, s, i;
+			pfx = ",";
+		}
+		printf " \\\n}\n\n";
+
+		printf "#define %s_FEATURE(x) \\\n", s;
+		printf "\t((( ";
+		for (i = 0; i < ncapints; i++) {
+			if (masks[i]) {
+				printf "\\\n\t\t((x) >> 5) == %2d ? %s_MASK%-3d : ", i, s, i;
+			}
+		}
+		printf "0 \\\n";
+		printf "\t) >> ((x) & 31)) & 1)\n\n";
+
+		printf "#define %s_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != %d)\n\n", s, ncapints;
+	}
+
+	printf "#define SSE_MASK\t\\\n";
+	printf "\t(REQUIRED_MASK0 & ((1<<(X86_FEATURE_XMM & 31)) | (1<<(X86_FEATURE_XMM2 & 31))))\n\n";
+
+	printf "#endif /* _ASM_X86_FEATUREMASKS_H */\n";
+}
-- 
2.45.0
Re: [RESEND v1 2/3] x86/cpufeatures: Generate a feature mask header based on build config
Posted by Xin Li 1 year, 6 months ago 
On 5/9/2024 1:53 PM, Xin Li (Intel) wrote:
> From: "H. Peter Anvin (Intel)" <hpa@zytor.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

...

> +
> +		printf "\n#define %s_MASKS ", s;
> +		pfx = "{";
> +		for (i = 0; i < ncapints; i++) {
> +			printf "%s \\\n\t%s_MASK_%d", pfx, s, i;
> +			pfx = ",";
> +		}
> +		printf " \\\n}\n\n";
> +
> +		printf "#define %s_FEATURE(x) \\\n", s;
> +		printf "\t((( ";
> +		for (i = 0; i < ncapints; i++) {
> +			if (masks[i]) {
> +				printf "\\\n\t\t((x) >> 5) == %2d ? %s_MASK%-3d : ", i, s, i;
> +			}
> +		}
> +		printf "0 \\\n";
> +		printf "\t) >> ((x) & 31)) & 1)\n\n";

This code generates 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.

But they are NOT currently used, so I prefer to remove them for now.

Thanks!
     Xin
Re: [RESEND v1 2/3] x86/cpufeatures: Generate a feature mask header based on build config
Posted by H. Peter Anvin 1 year, 5 months ago 
On June 16, 2024 12:26:48 AM PDT, Xin Li <xin@zytor.com> wrote:
>On 5/9/2024 1:53 PM, Xin Li (Intel) wrote:
>> From: "H. Peter Anvin (Intel)" <hpa@zytor.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
>
>...
>
>> +
>> +		printf "\n#define %s_MASKS ", s;
>> +		pfx = "{";
>> +		for (i = 0; i < ncapints; i++) {
>> +			printf "%s \\\n\t%s_MASK_%d", pfx, s, i;
>> +			pfx = ",";
>> +		}
>> +		printf " \\\n}\n\n";
>> +
>> +		printf "#define %s_FEATURE(x) \\\n", s;
>> +		printf "\t((( ";
>> +		for (i = 0; i < ncapints; i++) {
>> +			if (masks[i]) {
>> +				printf "\\\n\t\t((x) >> 5) == %2d ? %s_MASK%-3d : ", i, s, i;
>> +			}
>> +		}
>> +		printf "0 \\\n";
>> +		printf "\t) >> ((x) & 31)) & 1)\n\n";
>
>This code generates 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.
>
>But they are NOT currently used, so I prefer to remove them for now.
>
>Thanks!
>    Xin

The goal with these is that it can eliminate the handwritten code that tests a long list of masks. Again, automation.
Re: [RESEND v1 2/3] x86/cpufeatures: Generate a feature mask header based on build config
Posted by Xin Li 1 year, 5 months ago 
On 6/17/2024 6:46 AM, H. Peter Anvin wrote:
> On June 16, 2024 12:26:48 AM PDT, Xin Li <xin@zytor.com> wrote:
>> On 5/9/2024 1:53 PM, Xin Li (Intel) wrote:
>>> From: "H. Peter Anvin (Intel)" <hpa@zytor.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
>>
>> ...
>>
>>> +
>>> +		printf "\n#define %s_MASKS ", s;
>>> +		pfx = "{";
>>> +		for (i = 0; i < ncapints; i++) {
>>> +			printf "%s \\\n\t%s_MASK_%d", pfx, s, i;
>>> +			pfx = ",";
>>> +		}
>>> +		printf " \\\n}\n\n";
>>> +
>>> +		printf "#define %s_FEATURE(x) \\\n", s;
>>> +		printf "\t((( ";
>>> +		for (i = 0; i < ncapints; i++) {
>>> +			if (masks[i]) {
>>> +				printf "\\\n\t\t((x) >> 5) == %2d ? %s_MASK%-3d : ", i, s, i;
>>> +			}
>>> +		}
>>> +		printf "0 \\\n";
>>> +		printf "\t) >> ((x) & 31)) & 1)\n\n";
>>
>> This code generates 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.
>>
>> But they are NOT currently used, so I prefer to remove them for now.
>>
>> Thanks!
>>     Xin
> 
> The goal with these is that it can eliminate the handwritten code that tests a long list of masks. Again, automation.
> 

This piece of code is added back in the last patch of v3:

https://lore.kernel.org/lkml/20240622171435.3725548-5-xin@zytor.com/

The generated macros {REQUIRED|DISABLED}_MASK_BIT_SET are way shorter
than that in the original form:

#define REQUIRED_FEATURE(x)                             \
         ((                                              \
                 ((x) >> 5) ==  0 ? REQUIRED_MASK0 :     \
                 ((x) >> 5) ==  1 ? REQUIRED_MASK1 :     \
                 ((x) >> 5) ==  3 ? REQUIRED_MASK3 : 0   \
         ) & (1 << ((x) & 31)))

#define REQUIRED_MASK_BIT_SET(x)                        \
         (REQUIRED_FEATURE(x) || BUILD_BUG_ON_ZERO(NCAPINTS != 22))

Thanks!
     Xin

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