diff mbox series

[v4,10/15] x86: Implement ARCH_HAS_KERNEL_FPU_SUPPORT

Message ID 20240329072441.591471-11-samuel.holland@sifive.com (mailing list archive)
State Handled Elsewhere
Headers show
Series Unified cross-architecture kernel-mode FPU API | expand

Commit Message

Samuel Holland March 29, 2024, 7:18 a.m. UTC 
x86 already provides kernel_fpu_begin() and kernel_fpu_end(), but in a
different header. Add a wrapper header, and export the CFLAGS
adjustments as found in lib/Makefile.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v1)

 arch/x86/Kconfig           |  1 +
 arch/x86/Makefile          | 20 ++++++++++++++++++++
 arch/x86/include/asm/fpu.h | 13 +++++++++++++
 3 files changed, 34 insertions(+)
 create mode 100644 arch/x86/include/asm/fpu.h

Comments

Dave Hansen March 29, 2024, 5:28 p.m. UTC | #1 
On 3/29/24 00:18, Samuel Holland wrote:
> +#
> +# CFLAGS for compiling floating point code inside the kernel.
> +#
> +CC_FLAGS_FPU := -msse -msse2
> +ifdef CONFIG_CC_IS_GCC
> +# Stack alignment mismatch, proceed with caution.
> +# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
> +# (8B stack alignment).
> +# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
> +#
> +# The "-msse" in the first argument is there so that the
> +# -mpreferred-stack-boundary=3 build error:
> +#
> +#  -mpreferred-stack-boundary=3 is not between 4 and 12
> +#
> +# can be triggered. Otherwise gcc doesn't complain.
> +CC_FLAGS_FPU += -mhard-float
> +CC_FLAGS_FPU += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
> +endif

I was expecting to see this (now duplicate) hunk come _out_ of
lib/Makefile somewhere in the series.

Did I miss that, or is there something keeping the duplicate there?
Samuel Holland March 29, 2024, 6:02 p.m. UTC | #2 
On 2024-03-29 12:28 PM, Dave Hansen wrote:
> On 3/29/24 00:18, Samuel Holland wrote:
>> +#
>> +# CFLAGS for compiling floating point code inside the kernel.
>> +#
>> +CC_FLAGS_FPU := -msse -msse2
>> +ifdef CONFIG_CC_IS_GCC
>> +# Stack alignment mismatch, proceed with caution.
>> +# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
>> +# (8B stack alignment).
>> +# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
>> +#
>> +# The "-msse" in the first argument is there so that the
>> +# -mpreferred-stack-boundary=3 build error:
>> +#
>> +#  -mpreferred-stack-boundary=3 is not between 4 and 12
>> +#
>> +# can be triggered. Otherwise gcc doesn't complain.
>> +CC_FLAGS_FPU += -mhard-float
>> +CC_FLAGS_FPU += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
>> +endif
> 
> I was expecting to see this (now duplicate) hunk come _out_ of
> lib/Makefile somewhere in the series.
> 
> Did I miss that, or is there something keeping the duplicate there?

This hunk is removed in patch 15/15, after the conversion of lib/test_fpu.c:

https://lore.kernel.org/linux-kernel/20240329072441.591471-16-samuel.holland@sifive.com/

Regards,
Samuel
diff mbox series

Patch

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 39886bab943a..7c9d032ee675 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -83,6 +83,7 @@  config X86
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_KCOV			if X86_64
+	select ARCH_HAS_KERNEL_FPU_SUPPORT
 	select ARCH_HAS_MEM_ENCRYPT
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 662d9d4033e6..5a5f5999c505 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -74,6 +74,26 @@  KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
 KBUILD_RUSTFLAGS += --target=$(objtree)/scripts/target.json
 KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2
 
+#
+# CFLAGS for compiling floating point code inside the kernel.
+#
+CC_FLAGS_FPU := -msse -msse2
+ifdef CONFIG_CC_IS_GCC
+# Stack alignment mismatch, proceed with caution.
+# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
+# (8B stack alignment).
+# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
+#
+# The "-msse" in the first argument is there so that the
+# -mpreferred-stack-boundary=3 build error:
+#
+#  -mpreferred-stack-boundary=3 is not between 4 and 12
+#
+# can be triggered. Otherwise gcc doesn't complain.
+CC_FLAGS_FPU += -mhard-float
+CC_FLAGS_FPU += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
+endif
+
 ifeq ($(CONFIG_X86_KERNEL_IBT),y)
 #
 # Kernel IBT has S_CET.NOTRACK_EN=0, as such the compilers must not generate
diff --git a/arch/x86/include/asm/fpu.h b/arch/x86/include/asm/fpu.h
new file mode 100644
index 000000000000..b2743fe19339
--- /dev/null
+++ b/arch/x86/include/asm/fpu.h
@@ -0,0 +1,13 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 SiFive
+ */
+
+#ifndef _ASM_X86_FPU_H
+#define _ASM_X86_FPU_H
+
+#include <asm/fpu/api.h>
+
+#define kernel_fpu_available()	true
+
+#endif /* ! _ASM_X86_FPU_H */