[PATCH 5/5] LoongArch: Allow usage of LSX/LASX in the kernel

From: Huacai Chen chenhuacai@loongson.cn

LoongArch inclusion bugzilla: https://gitee.com/openeuler/kernel/issues/I76XQZ

Allow usage of LSX/LASX in the kernel by extending kernel_fpu_begin() and kernel_fpu_end().

Reviewed-by: WANG Xuerui git@xen0n.name Signed-off-by: Huacai Chen chenhuacai@loongson.cn --- arch/loongarch/kernel/kfpu.c | 55 +++++++++++++++++++++++++++++++++--- 1 file changed, 51 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/kernel/kfpu.c b/arch/loongarch/kernel/kfpu.c index 5c46ae8c6cac..ec5b28e570c9 100644 --- a/arch/loongarch/kernel/kfpu.c +++ b/arch/loongarch/kernel/kfpu.c @@ -8,19 +8,40 @@ #include <asm/fpu.h> #include <asm/smp.h>

+static unsigned int euen_mask = CSR_EUEN_FPEN; + +/* + * The critical section between kernel_fpu_begin() and kernel_fpu_end() + * is non-reentrant. It is the caller's responsibility to avoid reentrance. + * See drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c as an example. + */ static DEFINE_PER_CPU(bool, in_kernel_fpu); +static DEFINE_PER_CPU(unsigned int, euen_current);

void kernel_fpu_begin(void) { + unsigned int *euen_curr; + preempt_disable();

WARN_ON(this_cpu_read(in_kernel_fpu));

this_cpu_write(in_kernel_fpu, true); + euen_curr = this_cpu_ptr(&euen_current);

- if (!is_fpu_owner()) - enable_fpu(); + *euen_curr = csr_xchg32(euen_mask, euen_mask, LOONGARCH_CSR_EUEN); + +#ifdef CONFIG_CPU_HAS_LASX + if (*euen_curr & CSR_EUEN_LASXEN) + _save_lasx(&current->thread.fpu); + else +#endif +#ifdef CONFIG_CPU_HAS_LSX + if (*euen_curr & CSR_EUEN_LSXEN) + _save_lsx(&current->thread.fpu); else +#endif + if (*euen_curr & CSR_EUEN_FPEN) _save_fp(&current->thread.fpu);

write_fcsr(LOONGARCH_FCSR0, 0); @@ -29,15 +50,41 @@ EXPORT_SYMBOL_GPL(kernel_fpu_begin);

void kernel_fpu_end(void) { + unsigned int *euen_curr; + WARN_ON(!this_cpu_read(in_kernel_fpu));

- if (!is_fpu_owner()) - disable_fpu(); + euen_curr = this_cpu_ptr(&euen_current); + +#ifdef CONFIG_CPU_HAS_LASX + if (*euen_curr & CSR_EUEN_LASXEN) + _restore_lasx(&current->thread.fpu); else +#endif +#ifdef CONFIG_CPU_HAS_LSX + if (*euen_curr & CSR_EUEN_LSXEN) + _restore_lsx(&current->thread.fpu); + else +#endif + if (*euen_curr & CSR_EUEN_FPEN) _restore_fp(&current->thread.fpu);

+ *euen_curr = csr_xchg32(*euen_curr, euen_mask, LOONGARCH_CSR_EUEN); + this_cpu_write(in_kernel_fpu, false);

preempt_enable(); } EXPORT_SYMBOL_GPL(kernel_fpu_end); + +static int __init init_euen_mask(void) +{ + if (cpu_has_lsx) + euen_mask |= CSR_EUEN_LSXEN; + + if (cpu_has_lasx) + euen_mask |= CSR_EUEN_LASXEN; + + return 0; +} +arch_initcall(init_euen_mask);