From e031a5f3f1eddb961a6ded8a21ab8189d8760860 Mon Sep 17 00:00:00 2001 From: Huacai Chen Date: Thu, 29 Jun 2023 20:58:44 +0800 Subject: [PATCH] LoongArch: Support dbar with different hints Traditionally, LoongArch uses "dbar 0" (full completion barrier) for everything. But the full completion barrier is a performance killer, so Loongson-3A6000 and newer processors have made finer granularity hints available: Bit4: ordering or completion (0: completion, 1: ordering) Bit3: barrier for previous read (0: true, 1: false) Bit2: barrier for previous write (0: true, 1: false) Bit1: barrier for succeeding read (0: true, 1: false) Bit0: barrier for succeeding write (0: true, 1: false) Hint 0x700: barrier for "read after read" from the same address, which is needed by LL-SC loops on old models (dbar 0x700 behaves the same as nop if such reordering is disabled on new models). This patch makes use of the various new hints for different kinds of memory barriers. It brings performance improvements on Loongson-3A6000 series, while not affecting the existing models because all variants are treated as 'dbar 0' there. Why override queued_spin_unlock()? After commit 01e3b958efe85a26d9b ("drivers: Remove explicit invocations of mmiowb()") we need a completion barrier in queued_spin_unlock(), but the generic implementation use smp_store_release() which only provide an ordering barrier. Signed-off-by: Jun Yi Signed-off-by: Huacai Chen --- arch/loongarch/include/asm/Kbuild | 1 - arch/loongarch/include/asm/barrier.h | 130 ++++++++++++++------------------- arch/loongarch/include/asm/io.h | 2 +- arch/loongarch/include/asm/qspinlock.h | 18 +++++ arch/loongarch/kernel/smp.c | 2 +- arch/loongarch/mm/tlbex.S | 6 +- 6 files changed, 78 insertions(+), 81 deletions(-) create mode 100644 arch/loongarch/include/asm/qspinlock.h diff --git a/arch/loongarch/include/asm/Kbuild b/arch/loongarch/include/asm/Kbuild index 77ad8e6..6b222f2 100644 --- a/arch/loongarch/include/asm/Kbuild +++ b/arch/loongarch/include/asm/Kbuild @@ -5,7 +5,6 @@ generic-y += mcs_spinlock.h generic-y += parport.h generic-y += early_ioremap.h generic-y += qrwlock.h -generic-y += qspinlock.h generic-y += rwsem.h generic-y += segment.h generic-y += user.h diff --git a/arch/loongarch/include/asm/barrier.h b/arch/loongarch/include/asm/barrier.h index cda9776..4b663f1 100644 --- a/arch/loongarch/include/asm/barrier.h +++ b/arch/loongarch/include/asm/barrier.h @@ -5,27 +5,56 @@ #ifndef __ASM_BARRIER_H #define __ASM_BARRIER_H -#define __sync() __asm__ __volatile__("dbar 0" : : : "memory") +/* + * Hint encoding: + * + * Bit4: ordering or completion (0: completion, 1: ordering) + * Bit3: barrier for previous read (0: true, 1: false) + * Bit2: barrier for previous write (0: true, 1: false) + * Bit1: barrier for succeeding read (0: true, 1: false) + * Bit0: barrier for succeeding write (0: true, 1: false) + * + * Hint 0x700: barrier for "read after read" from the same address + */ + +#define DBAR(hint) __asm__ __volatile__("dbar %0 " : : "I"(hint) : "memory") + +#define crwrw 0b00000 +#define cr_r_ 0b00101 +#define c_w_w 0b01010 -#define fast_wmb() __sync() -#define fast_rmb() __sync() -#define fast_mb() __sync() -#define fast_iob() __sync() -#define wbflush() __sync() +#define orwrw 0b10000 +#define or_r_ 0b10101 +#define o_w_w 0b11010 -#define wmb() fast_wmb() -#define rmb() fast_rmb() -#define mb() fast_mb() -#define iob() fast_iob() +#define orw_w 0b10010 +#define or_rw 0b10100 -#define __smp_mb() __asm__ __volatile__("dbar 0" : : : "memory") -#define __smp_rmb() __asm__ __volatile__("dbar 0" : : : "memory") -#define __smp_wmb() __asm__ __volatile__("dbar 0" : : : "memory") +#define c_sync() DBAR(crwrw) +#define c_rsync() DBAR(cr_r_) +#define c_wsync() DBAR(c_w_w) + +#define o_sync() DBAR(orwrw) +#define o_rsync() DBAR(or_r_) +#define o_wsync() DBAR(o_w_w) + +#define ldacq_mb() DBAR(or_rw) +#define strel_mb() DBAR(orw_w) + +#define mb() c_sync() +#define rmb() c_rsync() +#define wmb() c_wsync() +#define iob() c_sync() +#define wbflush() c_sync() + +#define __smp_mb() o_sync() +#define __smp_rmb() o_rsync() +#define __smp_wmb() o_wsync() #ifdef CONFIG_SMP -#define __WEAK_LLSC_MB " dbar 0 \n" +#define __WEAK_LLSC_MB " dbar 0x700 \n" #else -#define __WEAK_LLSC_MB " \n" +#define __WEAK_LLSC_MB " \n" #endif #define __smp_mb__before_atomic() barrier() @@ -59,68 +88,19 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, return mask; } -#define __smp_load_acquire(p) \ -({ \ - union { typeof(*p) __val; char __c[1]; } __u; \ - unsigned long __tmp = 0; \ - compiletime_assert_atomic_type(*p); \ - switch (sizeof(*p)) { \ - case 1: \ - *(__u8 *)__u.__c = *(volatile __u8 *)p; \ - __smp_mb(); \ - break; \ - case 2: \ - *(__u16 *)__u.__c = *(volatile __u16 *)p; \ - __smp_mb(); \ - break; \ - case 4: \ - __asm__ __volatile__( \ - "amor_db.w %[val], %[tmp], %[mem] \n" \ - : [val] "=&r" (*(__u32 *)__u.__c) \ - : [mem] "ZB" (*(u32 *) p), [tmp] "r" (__tmp) \ - : "memory"); \ - break; \ - case 8: \ - __asm__ __volatile__( \ - "amor_db.d %[val], %[tmp], %[mem] \n" \ - : [val] "=&r" (*(__u64 *)__u.__c) \ - : [mem] "ZB" (*(u64 *) p), [tmp] "r" (__tmp) \ - : "memory"); \ - break; \ - } \ - (typeof(*p))__u.__val; \ +#define __smp_load_acquire(p) \ +({ \ + typeof(*p) ___p1 = READ_ONCE(*p); \ + compiletime_assert_atomic_type(*p); \ + ldacq_mb(); \ + ___p1; \ }) -#define __smp_store_release(p, v) \ -do { \ - union { typeof(*p) __val; char __c[1]; } __u = \ - { .__val = (__force typeof(*p)) (v) }; \ - unsigned long __tmp; \ - compiletime_assert_atomic_type(*p); \ - switch (sizeof(*p)) { \ - case 1: \ - __smp_mb(); \ - *(volatile __u8 *)p = *(__u8 *)__u.__c; \ - break; \ - case 2: \ - __smp_mb(); \ - *(volatile __u16 *)p = *(__u16 *)__u.__c; \ - break; \ - case 4: \ - __asm__ __volatile__( \ - "amswap_db.w %[tmp], %[val], %[mem] \n" \ - : [mem] "+ZB" (*(u32 *)p), [tmp] "=&r" (__tmp) \ - : [val] "r" (*(__u32 *)__u.__c) \ - : ); \ - break; \ - case 8: \ - __asm__ __volatile__( \ - "amswap_db.d %[tmp], %[val], %[mem] \n" \ - : [mem] "+ZB" (*(u64 *)p), [tmp] "=&r" (__tmp) \ - : [val] "r" (*(__u64 *)__u.__c) \ - : ); \ - break; \ - } \ +#define __smp_store_release(p, v) \ +do { \ + compiletime_assert_atomic_type(*p); \ + strel_mb(); \ + WRITE_ONCE(*p, v); \ } while (0) #define __smp_store_mb(p, v) \ diff --git a/arch/loongarch/include/asm/io.h b/arch/loongarch/include/asm/io.h index 545e2708f..1c94102 100644 --- a/arch/loongarch/include/asm/io.h +++ b/arch/loongarch/include/asm/io.h @@ -62,7 +62,7 @@ extern pgprot_t pgprot_wc; #define ioremap_cache(offset, size) \ ioremap_prot((offset), (size), pgprot_val(PAGE_KERNEL)) -#define mmiowb() asm volatile ("dbar 0" ::: "memory") +#define mmiowb() wmb() /* * String version of I/O memory access operations. diff --git a/arch/loongarch/include/asm/qspinlock.h b/arch/loongarch/include/asm/qspinlock.h new file mode 100644 index 0000000..34f43f8 --- /dev/null +++ b/arch/loongarch/include/asm/qspinlock.h @@ -0,0 +1,18 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_QSPINLOCK_H +#define _ASM_QSPINLOCK_H + +#include + +#define queued_spin_unlock queued_spin_unlock + +static inline void queued_spin_unlock(struct qspinlock *lock) +{ + compiletime_assert_atomic_type(lock->locked); + c_sync(); + WRITE_ONCE(lock->locked, 0); +} + +#include + +#endif /* _ASM_QSPINLOCK_H */ diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c index 255967f..8ea1bbc 100644 --- a/arch/loongarch/kernel/smp.c +++ b/arch/loongarch/kernel/smp.c @@ -115,7 +115,7 @@ static u32 ipi_read_clear(int cpu) action = iocsr_read32(LOONGARCH_IOCSR_IPI_STATUS); /* Clear the ipi register to clear the interrupt */ iocsr_write32(action, LOONGARCH_IOCSR_IPI_CLEAR); - smp_mb(); + wbflush(); return action; } diff --git a/arch/loongarch/mm/tlbex.S b/arch/loongarch/mm/tlbex.S index 244e2f5..240ced5 100644 --- a/arch/loongarch/mm/tlbex.S +++ b/arch/loongarch/mm/tlbex.S @@ -184,7 +184,7 @@ tlb_huge_update_load: ertn nopage_tlb_load: - dbar 0 + dbar 0x700 csrrd ra, EXCEPTION_KS2 la_abs t0, tlb_do_page_fault_0 jr t0 @@ -333,7 +333,7 @@ tlb_huge_update_store: ertn nopage_tlb_store: - dbar 0 + dbar 0x700 csrrd ra, EXCEPTION_KS2 la_abs t0, tlb_do_page_fault_1 jr t0 @@ -480,7 +480,7 @@ tlb_huge_update_modify: ertn nopage_tlb_modify: - dbar 0 + dbar 0x700 csrrd ra, EXCEPTION_KS2 la_abs t0, tlb_do_page_fault_1 jr t0 -- 2.7.4