From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41990) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fLHSe-0007q6-Q3 for qemu-devel@nongnu.org; Tue, 22 May 2018 20:17:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fLHSb-0000Xt-Hy for qemu-devel@nongnu.org; Tue, 22 May 2018 20:17:00 -0400 Received: from mail-pl0-x241.google.com ([2607:f8b0:400e:c01::241]:34853) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fLHSb-0000Wb-9l for qemu-devel@nongnu.org; Tue, 22 May 2018 20:16:57 -0400 Received: by mail-pl0-x241.google.com with SMTP id i5-v6so11868393plt.2 for ; Tue, 22 May 2018 17:16:57 -0700 (PDT) From: Michael Clark Date: Wed, 23 May 2018 12:14:50 +1200 Message-Id: <1527034517-7851-4-git-send-email-mjc@sifive.com> In-Reply-To: <1527034517-7851-1-git-send-email-mjc@sifive.com> References: <1527034517-7851-1-git-send-email-mjc@sifive.com> Subject: [Qemu-devel] [PATCH v1 03/30] RISC-V: Use atomic_cmpxchg to update PLIC bitmaps List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: patches@groups.riscv.org, Michael Clark , Sagar Karandikar , Bastian Koppelmann , Palmer Dabbelt , Alistair Francis The PLIC previously used a mutex to protect against concurrent access to the claimed and pending bitfields. Instead of using a mutex, we update the bitfields using atomic_cmpxchg. Rename sifive_plic_num_irqs_pending to sifive_plic_irqs_pending and add an early out if any interrupts are pending as the count of pending interrupts is not used. Cc: Sagar Karandikar Cc: Bastian Koppelmann Cc: Palmer Dabbelt Cc: Alistair Francis Signed-off-by: Michael Clark Reviewed-by: Richard Henderson --- hw/riscv/sifive_plic.c | 49 +++++++++++++++++++----------------------- include/hw/riscv/sifive_plic.h | 1 - 2 files changed, 22 insertions(+), 28 deletions(-) diff --git a/hw/riscv/sifive_plic.c b/hw/riscv/sifive_plic.c index 874de2ebaf77..1af23c76e603 100644 --- a/hw/riscv/sifive_plic.c +++ b/hw/riscv/sifive_plic.c @@ -81,36 +81,32 @@ static void sifive_plic_print_state(SiFivePLICState *plic) } } -static -void sifive_plic_set_pending(SiFivePLICState *plic, int irq, bool pending) +static uint32_t atomic_set_masked(uint32_t *a, uint32_t mask, uint32_t value) { - qemu_mutex_lock(&plic->lock); - uint32_t word = irq >> 5; - if (pending) { - plic->pending[word] |= (1 << (irq & 31)); - } else { - plic->pending[word] &= ~(1 << (irq & 31)); - } - qemu_mutex_unlock(&plic->lock); + uint32_t old, new, cmp = atomic_read(a); + + do { + old = cmp; + new = (old & ~mask) | (value & mask); + cmp = atomic_cmpxchg(a, old, new); + } while (old != cmp); + + return old; } -static -void sifive_plic_set_claimed(SiFivePLICState *plic, int irq, bool claimed) +static void sifive_plic_set_pending(SiFivePLICState *plic, int irq, bool level) { - qemu_mutex_lock(&plic->lock); - uint32_t word = irq >> 5; - if (claimed) { - plic->claimed[word] |= (1 << (irq & 31)); - } else { - plic->claimed[word] &= ~(1 << (irq & 31)); - } - qemu_mutex_unlock(&plic->lock); + atomic_set_masked(&plic->pending[irq >> 5], 1 << (irq & 31), -!!level); } -static -int sifive_plic_num_irqs_pending(SiFivePLICState *plic, uint32_t addrid) +static void sifive_plic_set_claimed(SiFivePLICState *plic, int irq, bool level) { - int i, j, count = 0; + atomic_set_masked(&plic->claimed[irq >> 5], 1 << (irq & 31), -!!level); +} + +static int sifive_plic_irqs_pending(SiFivePLICState *plic, uint32_t addrid) +{ + int i, j; for (i = 0; i < plic->bitfield_words; i++) { uint32_t pending_enabled_not_claimed = (plic->pending[i] & ~plic->claimed[i]) & @@ -123,11 +119,11 @@ int sifive_plic_num_irqs_pending(SiFivePLICState *plic, uint32_t addrid) uint32_t prio = plic->source_priority[irq]; int enabled = pending_enabled_not_claimed & (1 << j); if (enabled && prio > plic->target_priority[addrid]) { - count++; + return 1; } } } - return count; + return 0; } static void sifive_plic_update(SiFivePLICState *plic) @@ -143,7 +139,7 @@ static void sifive_plic_update(SiFivePLICState *plic) if (!env) { continue; } - int level = sifive_plic_num_irqs_pending(plic, addrid) > 0; + int level = sifive_plic_irqs_pending(plic, addrid); switch (mode) { case PLICMode_M: riscv_set_local_interrupt(RISCV_CPU(cpu), MIP_MEIP, level); @@ -440,7 +436,6 @@ static void sifive_plic_realize(DeviceState *dev, Error **errp) memory_region_init_io(&plic->mmio, OBJECT(dev), &sifive_plic_ops, plic, TYPE_SIFIVE_PLIC, plic->aperture_size); parse_hart_config(plic); - qemu_mutex_init(&plic->lock); plic->bitfield_words = (plic->num_sources + 31) >> 5; plic->source_priority = g_new0(uint32_t, plic->num_sources); plic->target_priority = g_new(uint32_t, plic->num_addrs); diff --git a/include/hw/riscv/sifive_plic.h b/include/hw/riscv/sifive_plic.h index 11a5a98df1f9..ff09a288261e 100644 --- a/include/hw/riscv/sifive_plic.h +++ b/include/hw/riscv/sifive_plic.h @@ -55,7 +55,6 @@ typedef struct SiFivePLICState { uint32_t *pending; uint32_t *claimed; uint32_t *enable; - QemuMutex lock; qemu_irq *irqs; /* config */ -- 2.7.0