[PATCH 8/8] powerpc/64s: remove paravirt from simple spinlocks (RFC only)

[Nicholas Piggin]

RFC until we settle on queued spinlocks for 64s and remove the
option to go back to simple locks. If other sub-archs want to keep
simple spinlocks, the code can be nicely simplified.
---
 arch/powerpc/include/asm/simple_spinlock.h | 61 +-------------------
 arch/powerpc/kvm/book3s_hv_rm_mmu.c        |  6 --
 arch/powerpc/lib/Makefile                  |  4 --
 arch/powerpc/lib/locks.c                   | 65 ----------------------
 4 files changed, 2 insertions(+), 134 deletions(-)
 delete mode 100644 arch/powerpc/lib/locks.c

diff --git a/arch/powerpc/include/asm/simple_spinlock.h b/arch/powerpc/include/asm/simple_spinlock.h
index e048c041c4a9..5f0980dea001 100644
--- a/arch/powerpc/include/asm/simple_spinlock.h
+++ b/arch/powerpc/include/asm/simple_spinlock.h
@@ -16,23 +16,10 @@
  * (the type definitions are in asm/simple_spinlock_types.h)
  */
 #include <linux/irqflags.h>
-#include <asm/paravirt.h>
-#ifdef CONFIG_PPC64
-#include <asm/paca.h>
-#endif
 #include <asm/synch.h>
 #include <asm/ppc-opcode.h>
 
-#ifdef CONFIG_PPC64
-/* use 0x800000yy when locked, where yy == CPU number */
-#ifdef __BIG_ENDIAN__
-#define LOCK_TOKEN	(*(u32 *)(&get_paca()->lock_token))
-#else
-#define LOCK_TOKEN	(*(u32 *)(&get_paca()->paca_index))
-#endif
-#else
 #define LOCK_TOKEN	1
-#endif
 
 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
 {
@@ -74,43 +61,14 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
 	return __arch_spin_trylock(lock) == 0;
 }
 
-/*
- * On a system with shared processors (that is, where a physical
- * processor is multiplexed between several virtual processors),
- * there is no point spinning on a lock if the holder of the lock
- * isn't currently scheduled on a physical processor.  Instead
- * we detect this situation and ask the hypervisor to give the
- * rest of our timeslice to the lock holder.
- *
- * So that we can tell which virtual processor is holding a lock,
- * we put 0x80000000 | smp_processor_id() in the lock when it is
- * held.  Conveniently, we have a word in the paca that holds this
- * value.
- */
-
-#if defined(CONFIG_PPC_SPLPAR)
-/* We only yield to the hypervisor if we are in shared processor mode */
-void splpar_spin_yield(arch_spinlock_t *lock);
-void splpar_rw_yield(arch_rwlock_t *lock);
-#else /* SPLPAR */
-static inline void splpar_spin_yield(arch_spinlock_t *lock) {};
-static inline void splpar_rw_yield(arch_rwlock_t *lock) {};
-#endif
-
 static inline void spin_yield(arch_spinlock_t *lock)
 {
-	if (is_shared_processor())
-		splpar_spin_yield(lock);
-	else
-		barrier();
+	barrier();
 }
 
 static inline void rw_yield(arch_rwlock_t *lock)
 {
-	if (is_shared_processor())
-		splpar_rw_yield(lock);
-	else
-		barrier();
+	barrier();
 }
 
 static inline void arch_spin_lock(arch_spinlock_t *lock)
@@ -120,8 +78,6 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
 			break;
 		do {
 			HMT_low();
-			if (is_shared_processor())
-				splpar_spin_yield(lock);
 		} while (unlikely(lock->slock != 0));
 		HMT_medium();
 	}
@@ -139,8 +95,6 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
 		local_irq_restore(flags);
 		do {
 			HMT_low();
-			if (is_shared_processor())
-				splpar_spin_yield(lock);
 		} while (unlikely(lock->slock != 0));
 		HMT_medium();
 		local_irq_restore(flags_dis);
@@ -166,13 +120,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
  * read-locks.
  */
 
-#ifdef CONFIG_PPC64
-#define __DO_SIGN_EXTEND	"extsw	%0,%0\n"
-#define WRLOCK_TOKEN		LOCK_TOKEN	/* it's negative */
-#else
-#define __DO_SIGN_EXTEND
 #define WRLOCK_TOKEN		(-1)
-#endif
 
 /*
  * This returns the old value in the lock + 1,
@@ -184,7 +132,6 @@ static inline long __arch_read_trylock(arch_rwlock_t *rw)
 
 	__asm__ __volatile__(
 "1:	" PPC_LWARX(%0,0,%1,1) "\n"
-	__DO_SIGN_EXTEND
 "	addic.		%0,%0,1\n\
 	ble-		2f\n"
 "	stwcx.		%0,0,%1\n\
@@ -227,8 +174,6 @@ static inline void arch_read_lock(arch_rwlock_t *rw)
 			break;
 		do {
 			HMT_low();
-			if (is_shared_processor())
-				splpar_rw_yield(rw);
 		} while (unlikely(rw->lock < 0));
 		HMT_medium();
 	}
@@ -241,8 +186,6 @@ static inline void arch_write_lock(arch_rwlock_t *rw)
 			break;
 		do {
 			HMT_low();
-			if (is_shared_processor())
-				splpar_rw_yield(rw);
 		} while (unlikely(rw->lock != 0));
 		HMT_medium();
 	}
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index 88da2764c1bb..909025083161 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -410,12 +410,6 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 				 &vcpu->arch.regs.gpr[4]);
 }
 
-#ifdef __BIG_ENDIAN__
-#define LOCK_TOKEN	(*(u32 *)(&get_paca()->lock_token))
-#else
-#define LOCK_TOKEN	(*(u32 *)(&get_paca()->paca_index))
-#endif
-
 static inline int is_mmio_hpte(unsigned long v, unsigned long r)
 {
 	return ((v & HPTE_V_ABSENT) &&
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index d66a645503eb..158e71abc14c 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -41,10 +41,6 @@ obj-$(CONFIG_PPC_BOOK3S_64) += copyuser_power7.o copypage_power7.o \
 obj64-y	+= copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
 	   memcpy_64.o memcpy_mcsafe_64.o
 
-ifndef CONFIG_PPC_QUEUED_SPINLOCKS
-obj64-$(CONFIG_SMP)	+= locks.o
-endif
-
 obj64-$(CONFIG_ALTIVEC)	+= vmx-helper.o
 obj64-$(CONFIG_KPROBES_SANITY_TEST)	+= test_emulate_step.o \
 					   test_emulate_step_exec_instr.o
diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
deleted file mode 100644
index e35fd1a16992..000000000000
--- a/arch/powerpc/lib/locks.c
+++ /dev/null
@@ -1,65 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * Spin and read/write lock operations.
- *
- * Copyright (C) 2001-2004 Paul Mackerras <paulus@xxxxxxxxxx>, IBM
- * Copyright (C) 2001 Anton Blanchard <anton@xxxxxxxxxx>, IBM
- * Copyright (C) 2002 Dave Engebretsen <engebret@xxxxxxxxxx>, IBM
- *   Rework to support virtual processors
- */
-
-#include <linux/kernel.h>
-#include <linux/spinlock.h>
-#include <linux/export.h>
-#include <linux/smp.h>
-
-/* waiting for a spinlock... */
-#if defined(CONFIG_PPC_SPLPAR)
-#include <asm/hvcall.h>
-#include <asm/smp.h>
-
-void splpar_spin_yield(arch_spinlock_t *lock)
-{
-	unsigned int lock_value, holder_cpu, yield_count;
-
-	lock_value = lock->slock;
-	if (lock_value == 0)
-		return;
-	holder_cpu = lock_value & 0xffff;
-	BUG_ON(holder_cpu >= NR_CPUS);
-
-	yield_count = yield_count_of(holder_cpu);
-	if ((yield_count & 1) == 0)
-		return;		/* virtual cpu is currently running */
-	smp_rmb();
-	if (lock->slock != lock_value)
-		return;		/* something has changed */
-	yield_to_preempted(holder_cpu, yield_count);
-}
-EXPORT_SYMBOL_GPL(splpar_spin_yield);
-
-/*
- * Waiting for a read lock or a write lock on a rwlock...
- * This turns out to be the same for read and write locks, since
- * we only know the holder if it is write-locked.
- */
-void splpar_rw_yield(arch_rwlock_t *rw)
-{
-	int lock_value;
-	unsigned int holder_cpu, yield_count;
-
-	lock_value = rw->lock;
-	if (lock_value >= 0)
-		return;		/* no write lock at present */
-	holder_cpu = lock_value & 0xffff;
-	BUG_ON(holder_cpu >= NR_CPUS);
-
-	yield_count = yield_count_of(holder_cpu);
-	if ((yield_count & 1) == 0)
-		return;		/* virtual cpu is currently running */
-	smp_rmb();
-	if (rw->lock != lock_value)
-		return;		/* something has changed */
-	yield_to_preempted(holder_cpu, yield_count);
-}
-#endif
-- 
2.23.0