powerpc: implement ARCH_HAS_KERNEL_FPU_SUPPORT

PowerPC provides an equivalent to the common kernel-mode FPU API, but in a
different header and using different function names.  The PowerPC API also
requires a non-preemptible context.  Add a wrapper header, and export the
CFLAGS adjustments.

Link: https://lkml.kernel.org/r/20240329072441.591471-9-samuel.holland@sifive.com
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: WANG Xuerui <git@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 56dcafbb83b3402e95c4354bad7a601a3049ec24..3c968f2f4ac44774398e76cf132698e0f18677e4 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -137,6 +137,7 @@ config PPC
        select ARCH_HAS_GCOV_PROFILE_ALL
        select ARCH_HAS_HUGEPD                  if HUGETLB_PAGE
        select ARCH_HAS_KCOV
+       select ARCH_HAS_KERNEL_FPU_SUPPORT      if PPC_FPU
        select ARCH_HAS_MEMBARRIER_CALLBACKS
        select ARCH_HAS_MEMBARRIER_SYNC_CORE
        select ARCH_HAS_MEMREMAP_COMPAT_ALIGN   if PPC_64S_HASH_MMU

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 0a0c57aee1ae04497e739dd92a605f6684eedade..a8479c881cac82bf61cce9fe8338b182053cdc0e 100644 (file)
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -149,6 +149,9 @@ CFLAGS-$(CONFIG_PPC32)      += $(call cc-option, $(MULTIPLEWORD))
 
 CFLAGS-$(CONFIG_PPC32) += $(call cc-option,-mno-readonly-in-sdata)
 
+CC_FLAGS_FPU           := $(call cc-option,-mhard-float)
+CC_FLAGS_NO_FPU                := $(call cc-option,-msoft-float)
+
 ifdef CONFIG_FUNCTION_TRACER
 ifdef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY
 KBUILD_CPPFLAGS        += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
@@ -170,7 +173,7 @@ asinstr := $(call as-instr,lis 9$(comma)foo@high,-DHAVE_AS_ATHIGH=1)
 
 KBUILD_CPPFLAGS        += -I $(srctree)/arch/powerpc $(asinstr)
 KBUILD_AFLAGS  += $(AFLAGS-y)
-KBUILD_CFLAGS  += $(call cc-option,-msoft-float)
+KBUILD_CFLAGS  += $(CC_FLAGS_NO_FPU)
 KBUILD_CFLAGS  += $(CFLAGS-y)
 CPP            = $(CC) -E $(KBUILD_CFLAGS)
 

diff --git a/arch/powerpc/include/asm/fpu.h b/arch/powerpc/include/asm/fpu.h
new file mode 100644 (file)
index 0000000..ca584e4
--- /dev/null
+++ b/arch/powerpc/include/asm/fpu.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 SiFive
+ */
+
+#ifndef _ASM_POWERPC_FPU_H
+#define _ASM_POWERPC_FPU_H
+
+#include <linux/preempt.h>
+
+#include <asm/cpu_has_feature.h>
+#include <asm/switch_to.h>
+
+#define kernel_fpu_available() (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
+
+static inline void kernel_fpu_begin(void)
+{
+       preempt_disable();
+       enable_kernel_fp();
+}
+
+static inline void kernel_fpu_end(void)
+{
+       disable_kernel_fp();
+       preempt_enable();
+}
+
+#endif /* ! _ASM_POWERPC_FPU_H */