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Message-ID: <95ddb5c5-57d4-4594-2712-863391f1c6c1@xen0n.name>
Date: Mon, 6 Mar 2023 11:21:25 +0800
From: WANG Xuerui <kernel@...0n.name>
To: Huacai Chen <chenhuacai@...ngson.cn>,
Arnd Bergmann <arnd@...db.de>,
Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev, linux-arch@...r.kernel.org,
Xuefeng Li <lixuefeng@...ngson.cn>,
Guo Ren <guoren@...nel.org>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH V2] LoongArch: Provide kernel fpu functions
On 2023/3/6 11:12, Huacai Chen wrote:
> Provide kernel_fpu_begin()/kernel_fpu_end() to allow the kernel itself
> to use fpu. They can be used by some other kernel components, e.g., the
> AMDGPU graphic driver for DCN.
IMO my previous explanation works better, but the current wording kinda
works for me. </grumble>
>
> Reported-by: WANG Xuerui<kernel@...0n.name>
One space before the opening angle bracket.
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
> V2: Use non-GPL exports and update commit messages.
>
> arch/loongarch/include/asm/fpu.h | 3 +++
> arch/loongarch/kernel/Makefile | 2 +-
> arch/loongarch/kernel/kfpu.c | 41 ++++++++++++++++++++++++++++++++
> 3 files changed, 45 insertions(+), 1 deletion(-)
> create mode 100644 arch/loongarch/kernel/kfpu.c
>
> diff --git a/arch/loongarch/include/asm/fpu.h b/arch/loongarch/include/asm/fpu.h
> index 358b254d9c1d..192f8e35d912 100644
> --- a/arch/loongarch/include/asm/fpu.h
> +++ b/arch/loongarch/include/asm/fpu.h
> @@ -21,6 +21,9 @@
>
> struct sigcontext;
>
> +extern void kernel_fpu_begin(void);
> +extern void kernel_fpu_end(void);
> +
> extern void _init_fpu(unsigned int);
> extern void _save_fp(struct loongarch_fpu *);
> extern void _restore_fp(struct loongarch_fpu *);
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 78d4e3384305..9a72d91cd104 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -13,7 +13,7 @@ obj-y += head.o cpu-probe.o cacheinfo.o env.o setup.o entry.o genex.o \
> obj-$(CONFIG_ACPI) += acpi.o
> obj-$(CONFIG_EFI) += efi.o
>
> -obj-$(CONFIG_CPU_HAS_FPU) += fpu.o
> +obj-$(CONFIG_CPU_HAS_FPU) += fpu.o kfpu.o
>
> obj-$(CONFIG_ARCH_STRICT_ALIGN) += unaligned.o
>
> diff --git a/arch/loongarch/kernel/kfpu.c b/arch/loongarch/kernel/kfpu.c
> new file mode 100644
> index 000000000000..cd2a18fecdcc
> --- /dev/null
> +++ b/arch/loongarch/kernel/kfpu.c
> @@ -0,0 +1,41 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
2020?
> + */
> +
> +#include <linux/cpu.h>
> +#include <linux/init.h>
> +#include <asm/fpu.h>
> +#include <asm/smp.h>
> +
> +static DEFINE_PER_CPU(bool, in_kernel_fpu);
> +
> +void kernel_fpu_begin(void)
> +{
> + if(this_cpu_read(in_kernel_fpu))
> + return;
You've ignored my WARN suggestion, but I could add it later anyway so
I'd allow this to go in as-is for now.
> +
> + preempt_disable();
> + this_cpu_write(in_kernel_fpu, true);
> +
> + if (!is_fpu_owner())
> + enable_fpu();
> + else
> + _save_fp(¤t->thread.fpu);
> +}
> +EXPORT_SYMBOL(kernel_fpu_begin);
> +
> +void kernel_fpu_end(void)
> +{
> + if(!this_cpu_read(in_kernel_fpu))
> + return;
> +
> + if (!is_fpu_owner())
> + disable_fpu();
> + else
> + _restore_fp(¤t->thread.fpu);
> +
> + this_cpu_write(in_kernel_fpu, false);
> + preempt_enable();
> +}
> +EXPORT_SYMBOL(kernel_fpu_end);
I've tested this along with the amdgpu DCN enablement, so:
Tested-by: WANG Xuerui <git@...0n.name>
--
WANG "xen0n" Xuerui
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