powerpc/64s: avoid reloading (H)SRR registers if they are still valid

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. These are cleared when returning from interrupt, when
using the registers for something else (e.g., OPAL calls), when
adjusting the return address or MSR of a context, and when context
switching (which changes the return address and MSR).

This improves the performance of interrupt returns.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fold in fixup patch from Nick]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210617155116.2167984-5-npiggin@gmail.com

6 files changed, 71 insertions, 15 deletions

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index 56a98936a6a9..19bcef666cf6 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -389,7 +389,15 @@ static inline bool arch_irq_disabled_regs(struct pt_regs *regs)
 	return !(regs->msr & MSR_EE);
 }
 
-static inline void may_hard_irq_enable(void) { }
+static inline bool may_hard_irq_enable(void)
+{
+	return false;
+}
+
+static inline void do_hard_irq_enable(void)
+{
+	BUILD_BUG();
+}
 
 static inline void irq_soft_mask_regs_set_state(struct pt_regs *regs, unsigned long val)
 {
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 59f704408d65..de36fb5d9c51 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -73,13 +73,25 @@
 #include <asm/kprobes.h>
 #include <asm/runlatch.h>
 
+#ifdef CONFIG_PPC_BOOK3S_64
+static inline void srr_regs_clobbered(void)
+{
+	local_paca->srr_valid = 0;
+	local_paca->hsrr_valid = 0;
+}
+#else
+static inline void srr_regs_clobbered(void)
+{
+}
+#endif
+
 static inline void nap_adjust_return(struct pt_regs *regs)
 {
 #ifdef CONFIG_PPC_970_NAP
 	if (unlikely(test_thread_local_flags(_TLF_NAPPING))) {
 		/* Can avoid a test-and-clear because NMIs do not call this */
 		clear_thread_local_flags(_TLF_NAPPING);
-		regs->nip = (unsigned long)power4_idle_nap_return;
+		regs_set_return_ip(regs, (unsigned long)power4_idle_nap_return);
 	}
 #endif
 }
diff --git a/arch/powerpc/include/asm/livepatch.h b/arch/powerpc/include/asm/livepatch.h
index ae25e6e72997..4fe018cc207b 100644
--- a/arch/powerpc/include/asm/livepatch.h
+++ b/arch/powerpc/include/asm/livepatch.h
@@ -16,7 +16,7 @@ static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
 {
 	struct pt_regs *regs = ftrace_get_regs(fregs);
 
-	regs->nip = ip;
+	regs_set_return_ip(regs, ip);
 }
 
 #define klp_get_ftrace_location klp_get_ftrace_location
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index ecc8d792a431..f5f0f3408047 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -168,6 +168,10 @@ struct paca_struct {
 #ifdef CONFIG_PPC_BOOK3E
 	u16 trap_save;			/* Used when bad stack is encountered */
 #endif
+#ifdef CONFIG_PPC_BOOK3S_64
+	u8 hsrr_valid;			/* HSRRs set for HRFID */
+	u8 srr_valid;			/* SRRs set for RFID */
+#endif
 	u8 irq_soft_mask;		/* mask for irq soft masking */
 	u8 irq_happened;		/* irq happened while soft-disabled */
 	u8 irq_work_pending;		/* IRQ_WORK interrupt while soft-disable */
diff --git a/arch/powerpc/include/asm/probes.h b/arch/powerpc/include/asm/probes.h
index 84dd1addd434..c5d984700d24 100644
--- a/arch/powerpc/include/asm/probes.h
+++ b/arch/powerpc/include/asm/probes.h
@@ -34,14 +34,14 @@ typedef u32 ppc_opcode_t;
 /* Enable single stepping for the current task */
 static inline void enable_single_step(struct pt_regs *regs)
 {
-	regs->msr |= MSR_SINGLESTEP;
+	regs_set_return_msr(regs, regs->msr | MSR_SINGLESTEP);
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 	/*
 	 * We turn off Critical Input Exception(CE) to ensure that the single
 	 * step will be for the instruction we have the probe on; if we don't,
 	 * it is possible we'd get the single step reported for CE.
 	 */
-	regs->msr &= ~MSR_CE;
+	regs_set_return_msr(regs, regs->msr & ~MSR_CE);
 	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
 #ifdef CONFIG_PPC_47x
 	isync();
diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index e06d61b668d4..5d69dafd80ad 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -123,6 +123,47 @@ struct pt_regs
 #endif /* __powerpc64__ */
 
 #ifndef __ASSEMBLY__
+#include <asm/paca.h>
+
+#ifdef CONFIG_SMP
+extern unsigned long profile_pc(struct pt_regs *regs);
+#else
+#define profile_pc(regs) instruction_pointer(regs)
+#endif
+
+long do_syscall_trace_enter(struct pt_regs *regs);
+void do_syscall_trace_leave(struct pt_regs *regs);
+
+static inline void regs_set_return_ip(struct pt_regs *regs, unsigned long ip)
+{
+	regs->nip = ip;
+#ifdef CONFIG_PPC_BOOK3S_64
+	local_paca->hsrr_valid = 0;
+	local_paca->srr_valid = 0;
+#endif
+}
+
+static inline void regs_set_return_msr(struct pt_regs *regs, unsigned long msr)
+{
+	regs->msr = msr;
+#ifdef CONFIG_PPC_BOOK3S_64
+	local_paca->hsrr_valid = 0;
+	local_paca->srr_valid = 0;
+#endif
+}
+
+static inline void set_return_regs_changed(void)
+{
+#ifdef CONFIG_PPC_BOOK3S_64
+	local_paca->hsrr_valid = 0;
+	local_paca->srr_valid = 0;
+#endif
+}
+
+static inline void regs_add_return_ip(struct pt_regs *regs, long offset)
+{
+	regs_set_return_ip(regs, regs->nip + offset);
+}
 
 static inline unsigned long instruction_pointer(struct pt_regs *regs)
 {
@@ -132,7 +173,7 @@ static inline unsigned long instruction_pointer(struct pt_regs *regs)
 static inline void instruction_pointer_set(struct pt_regs *regs,
 		unsigned long val)
 {
-	regs->nip = val;
+	regs_set_return_ip(regs, val);
 }
 
 static inline unsigned long user_stack_pointer(struct pt_regs *regs)
@@ -145,15 +186,6 @@ static inline unsigned long frame_pointer(struct pt_regs *regs)
 	return 0;
 }
 
-#ifdef CONFIG_SMP
-extern unsigned long profile_pc(struct pt_regs *regs);
-#else
-#define profile_pc(regs) instruction_pointer(regs)
-#endif
-
-long do_syscall_trace_enter(struct pt_regs *regs);
-void do_syscall_trace_leave(struct pt_regs *regs);
-
 #ifdef __powerpc64__
 #define user_mode(regs) ((((regs)->msr) >> MSR_PR_LG) & 0x1)
 #else