ARCv2: fpu: preserve userspace fpu state (f45ba2bd) · Commits · 戴 / test

arch/arc/Kconfig

+5 −10

Original line number	Diff line number	Diff line
		@@ -351,9 +351,8 @@ config NODES_SHIFT
		Accessing memory beyond 1GB (with or w/o PAE) requires 2 memory
		zones.

		if ISA_ARCOMPACT

		config ARC_COMPACT_IRQ_LEVELS
		depends on ISA_ARCOMPACT
		bool "Setup Timer IRQ as high Priority"
		# if SMP, LV2 enabled ONLY if ARC implementation has LV2 re-entrancy
		depends on !SMP
		@@ -361,14 +360,10 @@ config ARC_COMPACT_IRQ_LEVELS
		config ARC_FPU_SAVE_RESTORE
		bool "Enable FPU state persistence across context switch"
		help
		Double Precision Floating Point unit had dedicated regs which
		need to be saved/restored across context-switch.
		Note that ARC FPU is overly simplistic, unlike say x86, which has
		hardware pieces to allow software to conditionally save/restore,
		based on actual usage of FPU by a task. Thus our implemn does
		this for all tasks in system.

		endif #ISA_ARCOMPACT
		ARCompact FPU has internal registers to assist with Double precision
		Floating Point operations. There are control and stauts registers
		for floating point exceptions and rounding modes. These are
		preserved across task context switch when enabled.

		config ARC_CANT_LLSC
		def_bool n

+2 −0

Original line number	Diff line number	Diff line
		@@ -39,6 +39,8 @@
		#define ARC_REG_CLUSTER_BCR 0xcf
		#define ARC_REG_AUX_ICCM 0x208 /* ICCM Base Addr (ARCv2) */
		#define ARC_REG_LPB_CTRL 0x488 /* ARCv2 Loop Buffer control */
		#define ARC_REG_FPU_CTRL 0x300
		#define ARC_REG_FPU_STATUS 0x301

		/* Common for ARCompact and ARCv2 status register */
		#define ARC_REG_STATUS32 0x0A

+27 −1

Original line number	Diff line number	Diff line
		@@ -11,6 +11,8 @@

		#include <asm/ptrace.h>

		#ifdef CONFIG_ISA_ARCOMPACT

		/* These DPFP regs need to be saved/restored across ctx-sw */
		struct arc_fpu {
		struct {
		@@ -18,11 +20,35 @@ struct arc_fpu {
		} aux_dpfp[2];
		};

		extern void fpu_save_restore(struct task_struct p, struct task_struct n);
		#define fpu_init_task(regs)

		#else

		/*
		* ARCv2 FPU Control aux register
		* - bits to enable Traps on Exceptions
		* - Rounding mode
		*
		* ARCv2 FPU Status aux register
		* - FPU exceptions flags (Inv, Div-by-Zero, overflow, underflow, inexact)
		* - Flag Write Enable to clear flags explicitly (vs. by fpu instructions
		* only
		*/

		struct arc_fpu {
		unsigned int ctrl, status;
		};

		extern void fpu_init_task(struct pt_regs *regs);

		#endif /* !CONFIG_ISA_ARCOMPACT */

		extern void fpu_save_restore(struct task_struct p, struct task_struct n);

		#else /* !CONFIG_ARC_FPU_SAVE_RESTORE */

		#define fpu_save_restore(p, n)
		#define fpu_init_task(regs)

		#endif /* CONFIG_ARC_FPU_SAVE_RESTORE */

+2 −0

Original line number	Diff line number	Diff line
		@@ -23,7 +23,9 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.o
		obj-$(CONFIG_JUMP_LABEL) += jump_label.o

		obj-$(CONFIG_ARC_FPU_SAVE_RESTORE) += fpu.o
		ifdef CONFIG_ISA_ARCOMPACT
		CFLAGS_fpu.o += -mdpfp
		endif

		ifdef CONFIG_ARC_DW2_UNWIND
		CFLAGS_ctx_sw.o += -fno-omit-frame-pointer

+27 −0

Original line number	Diff line number	Diff line
		@@ -8,6 +8,8 @@
		#include <linux/sched.h>
		#include <asm/fpu.h>

		#ifdef CONFIG_ISA_ARCOMPACT

		/*
		* To save/restore FPU regs, simplest scheme would use LR/SR insns.
		* However since SR serializes the pipeline, an alternate "hack" can be used
		@@ -50,3 +52,28 @@ void fpu_save_restore(struct task_struct prev, struct task_struct next)
		: "r" (zero), "r" ((readfrom + 3)), "r" ((readfrom + 2))
		);
		}

		#else

		void fpu_init_task(struct pt_regs *regs)
		{
		/* default rounding mode */
		write_aux_reg(ARC_REG_FPU_CTRL, 0x100);

		/* set "Write enable" to allow explicit write to exception flags */
		write_aux_reg(ARC_REG_FPU_STATUS, 0x80000000);
		}

		void fpu_save_restore(struct task_struct prev, struct task_struct next)
		{
		struct arc_fpu *save = &prev->thread.fpu;
		struct arc_fpu *restore = &next->thread.fpu;

		save->ctrl = read_aux_reg(ARC_REG_FPU_CTRL);
		save->status = read_aux_reg(ARC_REG_FPU_STATUS);

		write_aux_reg(ARC_REG_FPU_CTRL, restore->ctrl);
		write_aux_reg(ARC_REG_FPU_STATUS, restore->status);
		}

		#endif