Re: [PATCH v6 5/5] Auto-detect whether a FPU exists
On Thu, Aug 09, 2018 at 03:44:40PM +0800, Alan Kao wrote: > We expect that a kernel with CONFIG_FPU=y can still support no-FPU > machines. To do so, the kernel should first examine the existence of a > FPU, then do nothing if a FPU does exist; otherwise, it should > disable/bypass all FPU-related functions. > > In this patch, a new global variable, has_fpu, is created and determined > when parsing the hardware capability from device tree during booting. > This variable is used in those FPU-related functions. > > Signed-off-by: Alan Kao > Cc: Greentime Hu > Cc: Vincent Chen > Cc: Zong Li > Cc: Nick Hu Looks good, Reviewed-by: Christoph Hellwig
Re: [PATCH v6 5/5] Auto-detect whether a FPU exists
On Thu, Aug 09, 2018 at 03:44:40PM +0800, Alan Kao wrote: > We expect that a kernel with CONFIG_FPU=y can still support no-FPU > machines. To do so, the kernel should first examine the existence of a > FPU, then do nothing if a FPU does exist; otherwise, it should > disable/bypass all FPU-related functions. > > In this patch, a new global variable, has_fpu, is created and determined > when parsing the hardware capability from device tree during booting. > This variable is used in those FPU-related functions. > > Signed-off-by: Alan Kao > Cc: Greentime Hu > Cc: Vincent Chen > Cc: Zong Li > Cc: Nick Hu Looks good, Reviewed-by: Christoph Hellwig
[PATCH v6 5/5] Auto-detect whether a FPU exists
We expect that a kernel with CONFIG_FPU=y can still support no-FPU machines. To do so, the kernel should first examine the existence of a FPU, then do nothing if a FPU does exist; otherwise, it should disable/bypass all FPU-related functions. In this patch, a new global variable, has_fpu, is created and determined when parsing the hardware capability from device tree during booting. This variable is used in those FPU-related functions. Signed-off-by: Alan Kao Cc: Greentime Hu Cc: Vincent Chen Cc: Zong Li Cc: Nick Hu --- arch/riscv/include/asm/switch_to.h | 8 arch/riscv/kernel/cpufeature.c | 8 arch/riscv/kernel/process.c| 4 +++- arch/riscv/kernel/signal.c | 6 -- 4 files changed, 19 insertions(+), 7 deletions(-) diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h index 093050b03543..733559083f24 100644 --- a/arch/riscv/include/asm/switch_to.h +++ b/arch/riscv/include/asm/switch_to.h @@ -56,13 +56,12 @@ static inline void __switch_to_aux(struct task_struct *prev, fstate_restore(next, task_pt_regs(next)); } -#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_INITIAL) - +extern bool has_fpu; #else +#define has_fpu false #define fstate_save(task, regs) do { } while (0) #define fstate_restore(task, regs) do { } while (0) #define __switch_to_aux(__prev, __next) do { } while (0) -#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_OFF) #endif extern struct task_struct *__switch_to(struct task_struct *, @@ -72,7 +71,8 @@ extern struct task_struct *__switch_to(struct task_struct *, do { \ struct task_struct *__prev = (prev);\ struct task_struct *__next = (next);\ - __switch_to_aux(__prev, __next);\ + if (has_fpu)\ + __switch_to_aux(__prev, __next);\ ((last) = __switch_to(__prev, __next)); \ } while (0) diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 17011a870044..46942e635266 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -22,6 +22,9 @@ #include unsigned long elf_hwcap __read_mostly; +#ifdef CONFIG_FPU +bool has_fpu __read_mostly; +#endif void riscv_fill_hwcap(void) { @@ -58,4 +61,9 @@ void riscv_fill_hwcap(void) elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])]; pr_info("elf_hwcap is 0x%lx", elf_hwcap); + +#ifdef CONFIG_FPU + if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)) + has_fpu = true; +#endif } diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 3820d89e2db9..97155aee9e71 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -83,7 +83,9 @@ void show_regs(struct pt_regs *regs) void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) { - regs->sstatus = DEFAULT_SSTATUS; + regs->sstatus = SR_SPIE; + if (has_fpu) + regs->sstatus |= SR_FS_INITIAL; regs->sepc = pc; regs->sp = sp; set_fs(USER_DS); diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index 2450b824d799..f9b5e7e352ef 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -98,7 +98,8 @@ static long restore_sigcontext(struct pt_regs *regs, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_from_user(regs, >sc_regs, sizeof(sc->sc_regs)); /* Restore the floating-point state. */ - err |= restore_fp_state(regs, >sc_fpregs); + if (has_fpu) + err |= restore_fp_state(regs, >sc_fpregs); return err; } @@ -150,7 +151,8 @@ static long setup_sigcontext(struct rt_sigframe __user *frame, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_to_user(>sc_regs, regs, sizeof(sc->sc_regs)); /* Save the floating-point state. */ - err |= save_fp_state(regs, >sc_fpregs); + if (has_fpu) + err |= save_fp_state(regs, >sc_fpregs); return err; } -- 2.18.0
[PATCH v6 5/5] Auto-detect whether a FPU exists
We expect that a kernel with CONFIG_FPU=y can still support no-FPU machines. To do so, the kernel should first examine the existence of a FPU, then do nothing if a FPU does exist; otherwise, it should disable/bypass all FPU-related functions. In this patch, a new global variable, has_fpu, is created and determined when parsing the hardware capability from device tree during booting. This variable is used in those FPU-related functions. Signed-off-by: Alan Kao Cc: Greentime Hu Cc: Vincent Chen Cc: Zong Li Cc: Nick Hu --- arch/riscv/include/asm/switch_to.h | 8 arch/riscv/kernel/cpufeature.c | 8 arch/riscv/kernel/process.c| 4 +++- arch/riscv/kernel/signal.c | 6 -- 4 files changed, 19 insertions(+), 7 deletions(-) diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h index 093050b03543..733559083f24 100644 --- a/arch/riscv/include/asm/switch_to.h +++ b/arch/riscv/include/asm/switch_to.h @@ -56,13 +56,12 @@ static inline void __switch_to_aux(struct task_struct *prev, fstate_restore(next, task_pt_regs(next)); } -#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_INITIAL) - +extern bool has_fpu; #else +#define has_fpu false #define fstate_save(task, regs) do { } while (0) #define fstate_restore(task, regs) do { } while (0) #define __switch_to_aux(__prev, __next) do { } while (0) -#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_OFF) #endif extern struct task_struct *__switch_to(struct task_struct *, @@ -72,7 +71,8 @@ extern struct task_struct *__switch_to(struct task_struct *, do { \ struct task_struct *__prev = (prev);\ struct task_struct *__next = (next);\ - __switch_to_aux(__prev, __next);\ + if (has_fpu)\ + __switch_to_aux(__prev, __next);\ ((last) = __switch_to(__prev, __next)); \ } while (0) diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 17011a870044..46942e635266 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -22,6 +22,9 @@ #include unsigned long elf_hwcap __read_mostly; +#ifdef CONFIG_FPU +bool has_fpu __read_mostly; +#endif void riscv_fill_hwcap(void) { @@ -58,4 +61,9 @@ void riscv_fill_hwcap(void) elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])]; pr_info("elf_hwcap is 0x%lx", elf_hwcap); + +#ifdef CONFIG_FPU + if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)) + has_fpu = true; +#endif } diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 3820d89e2db9..97155aee9e71 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -83,7 +83,9 @@ void show_regs(struct pt_regs *regs) void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) { - regs->sstatus = DEFAULT_SSTATUS; + regs->sstatus = SR_SPIE; + if (has_fpu) + regs->sstatus |= SR_FS_INITIAL; regs->sepc = pc; regs->sp = sp; set_fs(USER_DS); diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index 2450b824d799..f9b5e7e352ef 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -98,7 +98,8 @@ static long restore_sigcontext(struct pt_regs *regs, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_from_user(regs, >sc_regs, sizeof(sc->sc_regs)); /* Restore the floating-point state. */ - err |= restore_fp_state(regs, >sc_fpregs); + if (has_fpu) + err |= restore_fp_state(regs, >sc_fpregs); return err; } @@ -150,7 +151,8 @@ static long setup_sigcontext(struct rt_sigframe __user *frame, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_to_user(>sc_regs, regs, sizeof(sc->sc_regs)); /* Save the floating-point state. */ - err |= save_fp_state(regs, >sc_fpregs); + if (has_fpu) + err |= save_fp_state(regs, >sc_fpregs); return err; } -- 2.18.0