diff options
author | Michael Clark <mjc@sifive.com> | 2018-04-10 20:02:46 +1200 |
---|---|---|
committer | Alistair Francis <alistair.francis@wdc.com> | 2018-09-04 13:19:31 -0700 |
commit | d78940ec5d07d3b514f2fd8f941c58118fce2815 (patch) | |
tree | 784811c909ed01f04daf697027ef9ea0edb1d52b /hw/riscv | |
parent | c3b03e5800a7151d3c746f40efceabdfdae08f85 (diff) | |
download | qemu-d78940ec5d07d3b514f2fd8f941c58118fce2815.zip qemu-d78940ec5d07d3b514f2fd8f941c58118fce2815.tar.gz qemu-d78940ec5d07d3b514f2fd8f941c58118fce2815.tar.bz2 |
RISC-V: Use atomic_cmpxchg to update PLIC bitmaps
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 <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: Michael Clark <mjc@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Diffstat (limited to 'hw/riscv')
-rw-r--r-- | hw/riscv/sifive_plic.c | 49 |
1 files changed, 22 insertions, 27 deletions
diff --git a/hw/riscv/sifive_plic.c b/hw/riscv/sifive_plic.c index a91aeb9..f635e6f 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); @@ -439,7 +435,6 @@ 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); |