From: "H. Peter Anvin (Intel)" <hpa@zytor.com>
Required and disabled feature masks completely rely on build configs,
i.e., once a build config is fixed, so are the feature masks. To prepare
for auto-generating a header with required and disabled feature masks
based on a build config, add feature Kconfig items:
- X86_REQUIRED_FEATURE_x
- X86_DISABLED_FEATURE_x
each of which may be set to "y" if and only if its preconditions from
current build config are met.
X86_CMPXCHG64 and X86_CMOV are required features, thus rename them to
X86_REQUIRED_FEATURE_CX8 and X86_REQUIRED_FEATURE_CMOV.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
---
Changes since v1:
* Keep the X86_{REQUIRED,DISABLED}_FEATURE_ prefixes solely in
arch/x86/Kconfig.cpufeatures (Borislav Petkov).
* Explain how config option names X86_{REQUIRED,DISABLED}_FEATURE_<name>
are formed (Borislav Petkov).
---
arch/x86/Kconfig | 4 +-
arch/x86/Kconfig.cpu | 12 +-
arch/x86/Kconfig.cpufeatures | 197 ++++++++++++++++++
arch/x86/include/asm/asm-prototypes.h | 2 +-
arch/x86/include/asm/atomic64_32.h | 2 +-
arch/x86/include/asm/bitops.h | 4 +-
arch/x86/include/asm/cmpxchg_32.h | 2 +-
arch/x86/include/asm/required-features.h | 4 +-
arch/x86/lib/Makefile | 2 +-
arch/x86/lib/cmpxchg8b_emu.S | 2 +-
lib/atomic64_test.c | 2 +-
.../arch/x86/include/asm/required-features.h | 4 +-
12 files changed, 213 insertions(+), 24 deletions(-)
create mode 100644 arch/x86/Kconfig.cpufeatures
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e4e27d44dc2b..1c1f73202903 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -131,7 +131,7 @@ config X86
select ARCH_SUPPORTS_AUTOFDO_CLANG
select ARCH_SUPPORTS_PROPELLER_CLANG if X86_64
select ARCH_USE_BUILTIN_BSWAP
- select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64
+ select ARCH_USE_CMPXCHG_LOCKREF if X86_REQUIRED_FEATURE_CX8
select ARCH_USE_MEMTEST
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
@@ -3191,4 +3191,6 @@ config HAVE_ATOMIC_IOMAP
source "arch/x86/kvm/Kconfig"
+source "arch/x86/Kconfig.cpufeatures"
+
source "arch/x86/Kconfig.assembler"
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 2a7279d80460..c439f9c61101 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -366,21 +366,11 @@ config X86_HAVE_PAE
def_bool y
depends on MCRUSOE || MEFFICEON || MCYRIXIII || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MK8 || MVIAC7 || MCORE2 || MATOM || X86_64
-config X86_CMPXCHG64
- def_bool y
- depends on X86_HAVE_PAE || M586TSC || M586MMX || MK6 || MK7
-
-# this should be set for all -march=.. options where the compiler
-# generates cmov.
-config X86_CMOV
- def_bool y
- depends on (MK8 || MK7 || MCORE2 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || MCRUSOE || MEFFICEON || X86_64 || MATOM || MGEODE_LX)
-
config X86_MINIMUM_CPU_FAMILY
int
default "64" if X86_64
default "6" if X86_32 && (MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || MEFFICEON || MATOM || MCORE2 || MK7 || MK8)
- default "5" if X86_32 && X86_CMPXCHG64
+ default "5" if X86_32 && X86_REQUIRED_FEATURE_CX8
default "4"
config X86_DEBUGCTLMSR
diff --git a/arch/x86/Kconfig.cpufeatures b/arch/x86/Kconfig.cpufeatures
new file mode 100644
index 000000000000..5ed24e45df87
--- /dev/null
+++ b/arch/x86/Kconfig.cpufeatures
@@ -0,0 +1,197 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# x86 feature bits (see arch/x86/include/asm/cpufeatures.h) that are
+# either REQUIRED to be enabled, or DISABLED (always ignored) for this
+# particular compile-time configuration. The tests for these features
+# are turned into compile-time constants via the generated
+# <asm/featuremasks.h>.
+#
+# The naming of these variables *must* match asm/cpufeatures.h, e.g.,
+# X86_FEATURE_ALWAYS <==> X86_REQUIRED_FEATURE_ALWAYS
+# X86_FEATURE_FRED <==> X86_DISABLED_FEATURE_FRED
+#
+# And these REQUIRED and DISABLED config options are manipulated in an
+# AWK script as the following example:
+#
+# +----------------------+
+# | X86_FRED = y ? |
+# +----------------------+
+# / \
+# Y / \ N
+# +-------------------------------------+ +-------------------------------+
+# | X86_DISABLED_FEATURE_FRED undefined | | X86_DISABLED_FEATURE_FRED = y |
+# +-------------------------------------+ +-------------------------------+
+# |
+# |
+# +-------------------------------------------+ |
+# | X86_FEATURE_FRED: feature word 12, bit 17 | ---->|
+# +-------------------------------------------+ |
+# |
+# |
+# +-------------------------------+
+# | set bit 17 of DISABLED_MASK12 |
+# +-------------------------------+
+#
+
+config X86_REQUIRED_FEATURE_ALWAYS
+ def_bool y
+
+config X86_REQUIRED_FEATURE_NOPL
+ def_bool y
+ depends on X86_64 || X86_P6_NOP
+
+config X86_REQUIRED_FEATURE_CX8
+ def_bool y
+ depends on X86_HAVE_PAE || M586TSC || M586MMX || MK6 || MK7
+
+# this should be set for all -march=.. options where the compiler
+# generates cmov.
+config X86_REQUIRED_FEATURE_CMOV
+ def_bool y
+ depends on (MK8 || MK7 || MCORE2 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || MCRUSOE || MEFFICEON || X86_64 || MATOM || MGEODE_LX)
+
+# this should be set for all -march= options where the compiler
+# generates movbe.
+config X86_REQUIRED_FEATURE_MOVBE
+ def_bool y
+ depends on MATOM
+
+config X86_REQUIRED_FEATURE_CPUID
+ def_bool y
+ depends on X86_64
+
+config X86_REQUIRED_FEATURE_UP
+ def_bool y
+ depends on !SMP
+
+config X86_REQUIRED_FEATURE_FPU
+ def_bool y
+ depends on !MATH_EMULATION
+
+config X86_REQUIRED_FEATURE_PAE
+ def_bool y
+ depends on X86_64 || X86_PAE
+
+config X86_REQUIRED_FEATURE_PSE
+ def_bool y
+ depends on X86_64 && !PARAVIRT_XXL
+
+config X86_REQUIRED_FEATURE_PGE
+ def_bool y
+ depends on X86_64 && !PARAVIRT_XXL
+
+config X86_REQUIRED_FEATURE_MSR
+ def_bool y
+ depends on X86_64
+
+config X86_REQUIRED_FEATURE_FXSR
+ def_bool y
+ depends on X86_64
+
+config X86_REQUIRED_FEATURE_XMM
+ def_bool y
+ depends on X86_64
+
+config X86_REQUIRED_FEATURE_XMM2
+ def_bool y
+ depends on X86_64
+
+config X86_REQUIRED_FEATURE_LM
+ def_bool y
+ depends on X86_64
+
+config X86_DISABLED_FEATURE_UMIP
+ def_bool y
+ depends on !X86_UMIP
+
+config X86_DISABLED_FEATURE_VME
+ def_bool y
+ depends on X86_64
+
+config X86_DISABLED_FEATURE_K6_MTRR
+ def_bool y
+ depends on X86_64
+
+config X86_DISABLED_FEATURE_CYRIX_ARR
+ def_bool y
+ depends on X86_64
+
+config X86_DISABLED_FEATURE_CENTAUR_MCR
+ def_bool y
+ depends on X86_64
+
+config X86_DISABLED_FEATURE_PCID
+ def_bool y
+ depends on !X86_64
+
+config X86_DISABLED_FEATURE_PKU
+ def_bool y
+ depends on !X86_INTEL_MEMORY_PROTECTION_KEYS
+
+config X86_DISABLED_FEATURE_OSPKE
+ def_bool y
+ depends on !X86_INTEL_MEMORY_PROTECTION_KEYS
+
+config X86_DISABLED_FEATURE_LA57
+ def_bool y
+ depends on !X86_5LEVEL
+
+config X86_DISABLED_FEATURE_PTI
+ def_bool y
+ depends on !MITIGATION_PAGE_TABLE_ISOLATION
+
+config X86_DISABLED_FEATURE_RETPOLINE
+ def_bool y
+ depends on !MITIGATION_RETPOLINE
+
+config X86_DISABLED_FEATURE_RETPOLINE_LFENCE
+ def_bool y
+ depends on !MITIGATION_RETPOLINE
+
+config X86_DISABLED_FEATURE_RETHUNK
+ def_bool y
+ depends on !MITIGATION_RETHUNK
+
+config X86_DISABLED_FEATURE_UNRET
+ def_bool y
+ depends on !MITIGATION_UNRET_ENTRY
+
+config X86_DISABLED_FEATURE_CALL_DEPTH
+ def_bool y
+ depends on !MITIGATION_CALL_DEPTH_TRACKING
+
+config X86_DISABLED_FEATURE_LAM
+ def_bool y
+ depends on !ADDRESS_MASKING
+
+config X86_DISABLED_FEATURE_ENQCMD
+ def_bool y
+ depends on !INTEL_IOMMU_SVM
+
+config X86_DISABLED_FEATURE_SGX
+ def_bool y
+ depends on !X86_SGX
+
+config X86_DISABLED_FEATURE_XENPV
+ def_bool y
+ depends on !XEN_PV
+
+config X86_DISABLED_FEATURE_TDX_GUEST
+ def_bool y
+ depends on !INTEL_TDX_GUEST
+
+config X86_DISABLED_FEATURE_USER_SHSTK
+ def_bool y
+ depends on !X86_USER_SHADOW_STACK
+
+config X86_DISABLED_FEATURE_IBT
+ def_bool y
+ depends on !X86_KERNEL_IBT
+
+config X86_DISABLED_FEATURE_FRED
+ def_bool y
+ depends on !X86_FRED
+
+config X86_DISABLED_FEATURE_SEV_SNP
+ def_bool y
+ depends on !KVM_AMD_SEV
diff --git a/arch/x86/include/asm/asm-prototypes.h b/arch/x86/include/asm/asm-prototypes.h
index 3674006e3974..66fe5009830e 100644
--- a/arch/x86/include/asm/asm-prototypes.h
+++ b/arch/x86/include/asm/asm-prototypes.h
@@ -16,7 +16,7 @@
#include <asm/gsseg.h>
#include <asm/nospec-branch.h>
-#ifndef CONFIG_X86_CMPXCHG64
+#ifndef CONFIG_X86_REQUIRED_FEATURE_CX8
extern void cmpxchg8b_emu(void);
#endif
diff --git a/arch/x86/include/asm/atomic64_32.h b/arch/x86/include/asm/atomic64_32.h
index 6c6e9b9f98a4..3dca0f13b59f 100644
--- a/arch/x86/include/asm/atomic64_32.h
+++ b/arch/x86/include/asm/atomic64_32.h
@@ -48,7 +48,7 @@ static __always_inline s64 arch_atomic64_read_nonatomic(const atomic64_t *v)
ATOMIC64_EXPORT(atomic64_##sym)
#endif
-#ifdef CONFIG_X86_CMPXCHG64
+#ifdef CONFIG_X86_REQUIRED_FEATURE_CX8
#define __alternative_atomic64(f, g, out, in...) \
asm volatile("call %c[func]" \
: ALT_OUTPUT_SP(out) \
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index b96d45944c59..ff6444311704 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -321,7 +321,7 @@ static __always_inline int variable_ffs(int x)
asm("bsfl %1,%0"
: "=r" (r)
: ASM_INPUT_RM (x), "0" (-1));
-#elif defined(CONFIG_X86_CMOV)
+#elif defined(CONFIG_X86_REQUIRED_FEATURE_CMOV)
asm("bsfl %1,%0\n\t"
"cmovzl %2,%0"
: "=&r" (r) : "rm" (x), "r" (-1));
@@ -378,7 +378,7 @@ static __always_inline int fls(unsigned int x)
asm("bsrl %1,%0"
: "=r" (r)
: ASM_INPUT_RM (x), "0" (-1));
-#elif defined(CONFIG_X86_CMOV)
+#elif defined(CONFIG_X86_REQUIRED_FEATURE_CMOV)
asm("bsrl %1,%0\n\t"
"cmovzl %2,%0"
: "=&r" (r) : "rm" (x), "rm" (-1));
diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
index fd1282a783dd..633ca915644a 100644
--- a/arch/x86/include/asm/cmpxchg_32.h
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -69,7 +69,7 @@ static __always_inline bool __try_cmpxchg64_local(volatile u64 *ptr, u64 *oldp,
return __arch_try_cmpxchg64(ptr, oldp, new,);
}
-#ifdef CONFIG_X86_CMPXCHG64
+#ifdef CONFIG_X86_REQUIRED_FEATURE_CX8
#define arch_cmpxchg64 __cmpxchg64
diff --git a/arch/x86/include/asm/required-features.h b/arch/x86/include/asm/required-features.h
index e9187ddd3d1f..cef8104c103c 100644
--- a/arch/x86/include/asm/required-features.h
+++ b/arch/x86/include/asm/required-features.h
@@ -23,13 +23,13 @@
# define NEED_PAE 0
#endif
-#ifdef CONFIG_X86_CMPXCHG64
+#ifdef CONFIG_X86_REQUIRED_FEATURE_CX8
# define NEED_CX8 (1<<(X86_FEATURE_CX8 & 31))
#else
# define NEED_CX8 0
#endif
-#if defined(CONFIG_X86_CMOV) || defined(CONFIG_X86_64)
+#if defined(CONFIG_X86_REQUIRED_FEATURE_CMOV) || defined(CONFIG_X86_64)
# define NEED_CMOV (1<<(X86_FEATURE_CMOV & 31))
#else
# define NEED_CMOV 0
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 98583a9dbab3..9d4e96157e81 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -49,7 +49,7 @@ ifeq ($(CONFIG_X86_32),y)
lib-y += string_32.o
lib-y += memmove_32.o
lib-y += cmpxchg8b_emu.o
-ifneq ($(CONFIG_X86_CMPXCHG64),y)
+ifneq ($(CONFIG_X86_REQUIRED_FEATURE_CX8),y)
lib-y += atomic64_386_32.o
endif
else
diff --git a/arch/x86/lib/cmpxchg8b_emu.S b/arch/x86/lib/cmpxchg8b_emu.S
index 1c96be769adc..4bc06bd1aee1 100644
--- a/arch/x86/lib/cmpxchg8b_emu.S
+++ b/arch/x86/lib/cmpxchg8b_emu.S
@@ -7,7 +7,7 @@
.text
-#ifndef CONFIG_X86_CMPXCHG64
+#ifndef CONFIG_X86_REQUIRED_FEATURE_CX8
/*
* Emulate 'cmpxchg8b (%esi)' on UP
diff --git a/lib/atomic64_test.c b/lib/atomic64_test.c
index 759ea1783cc5..c85e8ab3f67d 100644
--- a/lib/atomic64_test.c
+++ b/lib/atomic64_test.c
@@ -254,7 +254,7 @@ static __init int test_atomics_init(void)
pr_info("passed for %s platform %s CX8 and %s SSE\n",
#ifdef CONFIG_X86_64
"x86-64",
-#elif defined(CONFIG_X86_CMPXCHG64)
+#elif defined(CONFIG_X86_REQUIRED_FEATURE_CX8)
"i586+",
#else
"i386+",
diff --git a/tools/arch/x86/include/asm/required-features.h b/tools/arch/x86/include/asm/required-features.h
index e9187ddd3d1f..cef8104c103c 100644
--- a/tools/arch/x86/include/asm/required-features.h
+++ b/tools/arch/x86/include/asm/required-features.h
@@ -23,13 +23,13 @@
# define NEED_PAE 0
#endif
-#ifdef CONFIG_X86_CMPXCHG64
+#ifdef CONFIG_X86_REQUIRED_FEATURE_CX8
# define NEED_CX8 (1<<(X86_FEATURE_CX8 & 31))
#else
# define NEED_CX8 0
#endif
-#if defined(CONFIG_X86_CMOV) || defined(CONFIG_X86_64)
+#if defined(CONFIG_X86_REQUIRED_FEATURE_CMOV) || defined(CONFIG_X86_64)
# define NEED_CMOV (1<<(X86_FEATURE_CMOV & 31))
#else
# define NEED_CMOV 0
--
2.47.1On Sun, Jan 05, 2025 at 11:07:23PM -0800, Xin Li (Intel) wrote:
> From: "H. Peter Anvin (Intel)" <hpa@zytor.com>
>
> Required and disabled feature masks completely rely on build configs,
> i.e., once a build config is fixed, so are the feature masks. To prepare
> for auto-generating a header with required and disabled feature masks
> based on a build config, add feature Kconfig items:
> - X86_REQUIRED_FEATURE_x
> - X86_DISABLED_FEATURE_x
> each of which may be set to "y" if and only if its preconditions from
> current build config are met.
>
> X86_CMPXCHG64 and X86_CMOV are required features, thus rename them to
> X86_REQUIRED_FEATURE_CX8 and X86_REQUIRED_FEATURE_CMOV.
>
> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: Xin Li (Intel) <xin@zytor.com>
> ---
>
> Changes since v1:
> * Keep the X86_{REQUIRED,DISABLED}_FEATURE_ prefixes solely in
> arch/x86/Kconfig.cpufeatures (Borislav Petkov).
But that isn't the case yet, right?
There are changes in the code like this now:
#include <asm/nospec-branch.h>
-#ifndef CONFIG_X86_CMPXCHG64
+#ifndef CONFIG_X86_REQUIRED_FEATURE_CX8
extern void cmpxchg8b_emu(void);
which means, I need to know whether I need to use a REQUIRED feature flag or
a normal feature flag, i.e., CONFIG_X86_CMPXCHG64.
Btw, why are you renaming CMPXCHG64 to CX8?
So what would be a lot nicer is if you did this in Kconfig.cpufeatures:
+ config X86_REQUIRED_FEATURE_CMPXCHG64
select X86_CMPXCHG64
+ def_bool y
+ depends on X86_HAVE_PAE || M586TSC || M586MMX || MK6 || MK7
and then use CONFIG_X86_CMPXCHG64 everywhere.
So that the rest of the code doesn't have to know whether those features are
REQUIRED or DISABLED but just features and only the internal machinery does
those additional defines.
Makes sense?
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
CX8 is the name of the CPUID flag, for better or worse. It seems to me to be a bit silly to have dummy symbols that mean literally the same thing, but ...
On Sat, Feb 15, 2025 at 02:12:35AM -0800, H. Peter Anvin wrote:
> CX8 is the name of the CPUID flag, for better or worse.
Right, so a separate patch:
git grep X86_CMPXCHG64
arch/x86/Kconfig:135: select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64
arch/x86/Kconfig.cpu:369:config X86_CMPXCHG64
arch/x86/Kconfig.cpu:383: default "5" if X86_32 && X86_CMPXCHG64
arch/x86/include/asm/asm-prototypes.h:19:#ifndef CONFIG_X86_CMPXCHG64
arch/x86/include/asm/atomic64_32.h:51:#ifdef CONFIG_X86_CMPXCHG64
arch/x86/include/asm/cmpxchg_32.h:72:#ifdef CONFIG_X86_CMPXCHG64
arch/x86/include/asm/required-features.h:26:#ifdef CONFIG_X86_CMPXCHG64
arch/x86/lib/Makefile:59:ifneq ($(CONFIG_X86_CMPXCHG64),y)
arch/x86/lib/cmpxchg8b_emu.S:10:#ifndef CONFIG_X86_CMPXCHG64
lib/atomic64_test.c:257:#elif defined(CONFIG_X86_CMPXCHG64)
tools/arch/x86/include/asm/required-features.h:26:#ifdef CONFIG_X86_CMPXCHG64
should be easy.
> It seems to me to be a bit silly to have dummy symbols that mean literally
> the same thing, but ...
Why if they're confined and encapsulated in a single file:
arch/x86/Kconfig.cpufeatures ?
Rest of the kernel doesn't need to know whether a feature is required or not,
right?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On February 15, 2025 6:20:17 AM PST, Borislav Petkov <bp@alien8.de> wrote: >On Sat, Feb 15, 2025 at 02:12:35AM -0800, H. Peter Anvin wrote: >> CX8 is the name of the CPUID flag, for better or worse. > >Right, so a separate patch: > >git grep X86_CMPXCHG64 >arch/x86/Kconfig:135: select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 >arch/x86/Kconfig.cpu:369:config X86_CMPXCHG64 >arch/x86/Kconfig.cpu:383: default "5" if X86_32 && X86_CMPXCHG64 >arch/x86/include/asm/asm-prototypes.h:19:#ifndef CONFIG_X86_CMPXCHG64 >arch/x86/include/asm/atomic64_32.h:51:#ifdef CONFIG_X86_CMPXCHG64 >arch/x86/include/asm/cmpxchg_32.h:72:#ifdef CONFIG_X86_CMPXCHG64 >arch/x86/include/asm/required-features.h:26:#ifdef CONFIG_X86_CMPXCHG64 >arch/x86/lib/Makefile:59:ifneq ($(CONFIG_X86_CMPXCHG64),y) >arch/x86/lib/cmpxchg8b_emu.S:10:#ifndef CONFIG_X86_CMPXCHG64 >lib/atomic64_test.c:257:#elif defined(CONFIG_X86_CMPXCHG64) >tools/arch/x86/include/asm/required-features.h:26:#ifdef CONFIG_X86_CMPXCHG64 > >should be easy. > >> It seems to me to be a bit silly to have dummy symbols that mean literally >> the same thing, but ... > >Why if they're confined and encapsulated in a single file: >arch/x86/Kconfig.cpufeatures ? > >Rest of the kernel doesn't need to know whether a feature is required or not, >right? > The point was that that is the *only* use of this particular flag, I believe.
On Sat, Feb 15, 2025 at 06:27:04AM -0800, H. Peter Anvin wrote:
> The point was that that is the *only* use of this particular flag, I believe.
Now you've confused me :-\. Perhaps elaborate a bit more what do you mean...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On February 15, 2025 6:30:32 AM PST, Borislav Petkov <bp@alien8.de> wrote: >On Sat, Feb 15, 2025 at 06:27:04AM -0800, H. Peter Anvin wrote: >> The point was that that is the *only* use of this particular flag, I believe. > >Now you've confused me :-\. Perhaps elaborate a bit more what do you mean... > A bunch of flags in Kconfig.cpu have exactly the meaning of "this CPU is guaranteed to have this feature."
On Sat, Feb 15, 2025 at 06:35:52AM -0800, H. Peter Anvin wrote:
> A bunch of flags in Kconfig.cpu have exactly the meaning of "this CPU is
> guaranteed to have this feature."
... and we won't add new ones which are required any time soon so we might as
well make the required ones really be called "REQUIRED" and have those defines
basically self-document themselves...?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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