Re: [PATCH 04/14] powerpc/64s: avoid reloading (H)SRR registers if they are still valid
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-04-04 00:50:15
Excerpts from Michael Ellerman's message of April 3, 2021 8:39 am:
Nicholas Piggin [off-list ref] writes:quoted
When an interrupt is taken, the SRR registers are set to return to where it left off. Unless they are modified in the meantime, or the return address or MSR are modified, there is no need to reload these registers when returning from interrupt. Introduce per-CPU flags that track the validity of SRR and HSRR registers, clear them when returning from interrupt, using the registers for something else (e.g., OPAL calls), or adjusting return address or MSR. This improves the performance of interrupt returns. XXX: may not need to invalidate both hsrr and srr all the time Signed-off-by: Nicholas Piggin <npiggin@gmail.com> ---I needed something like below to get 32-bit building.
That looks much better. Thanks, Nick
quoted hunk ↗ jump to hunk
cheersdiff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h index 6d6237e0cbd7..7f9bbd19db10 100644 --- a/arch/powerpc/include/asm/ptrace.h +++ b/arch/powerpc/include/asm/ptrace.h@@ -153,15 +153,21 @@ static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc) regs->gpr[3] = rc; } -static inline void regs_set_return_ip(struct pt_regs *regs, unsigned long ip) +static inline void invalidate_srrs(void) { - regs->nip = ip; #ifdef CONFIG_PPC_BOOK3S_64 + // XXX: We may not need to invalidate both hsrr and srr all the time local_paca->hsrr_valid = 0; local_paca->srr_valid = 0; #endif } +static inline void regs_set_return_ip(struct pt_regs *regs, unsigned long ip) +{ + regs->nip = ip; + invalidate_srrs(); +} + static inline void regs_add_return_ip(struct pt_regs *regs, long offset) { regs_set_return_ip(regs, regs->nip + offset);diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 200b4805f999..82623b57e2d6 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c@@ -98,8 +98,7 @@ static void check_if_tm_restore_required(struct task_struct *tsk) !test_thread_flag(TIF_RESTORE_TM)) { tsk->thread.ckpt_regs.msr = tsk->thread.regs->msr; set_thread_flag(TIF_RESTORE_TM); - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); } }@@ -164,8 +163,7 @@ static void __giveup_fpu(struct task_struct *tsk) if (cpu_has_feature(CPU_FTR_VSX)) msr &= ~MSR_VSX; tsk->thread.regs->msr = msr; - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); } void giveup_fpu(struct task_struct *tsk)@@ -249,8 +247,7 @@ static void __giveup_altivec(struct task_struct *tsk) if (cpu_has_feature(CPU_FTR_VSX)) msr &= ~MSR_VSX; tsk->thread.regs->msr = msr; - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); } void giveup_altivec(struct task_struct *tsk)@@ -566,8 +563,7 @@ void notrace restore_math(struct pt_regs *regs) msr_check_and_clear(new_msr); regs->msr |= new_msr | fpexc_mode; - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); } } #endif /* CONFIG_PPC_BOOK3S_64 */@@ -1293,8 +1289,7 @@ struct task_struct *__switch_to(struct task_struct *prev, atomic_read(¤t->mm->context.vas_windows))) asm volatile(PPC_CP_ABORT); } - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); #endif /* CONFIG_PPC_BOOK3S_64 */ return last;@@ -1884,8 +1879,7 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp) current->thread.load_tm = 0; #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */ - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); } EXPORT_SYMBOL(start_thread);@@ -1936,8 +1930,7 @@ int set_fpexc_mode(struct task_struct *tsk, unsigned int val) if (regs != NULL && (regs->msr & MSR_FP) != 0) { regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1)) | tsk->thread.fpexc_mode; - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); } return 0; }@@ -1990,8 +1983,7 @@ int set_endian(struct task_struct *tsk, unsigned int val) else return -EINVAL; - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); return 0; }diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c index 4cb38afa28a8..9d1d6070a516 100644 --- a/arch/powerpc/kernel/syscalls.c +++ b/arch/powerpc/kernel/syscalls.c@@ -115,8 +115,8 @@ SYSCALL_DEFINE0(switch_endian) struct thread_info *ti; current->thread.regs->msr ^= MSR_LE; - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + + invalidate_srrs(); /* * Set TIF_RESTOREALL so that r3 isn't clobbered on return todiff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index 96505d4bba1c..2b94bf21d6ae 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c@@ -3480,8 +3480,7 @@ int emulate_step(struct pt_regs *regs, struct ppc_inst instr) unsigned long val; unsigned long ea; - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + invalidate_srrs(); r = analyse_instr(&op, regs, instr); if (r < 0)