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 <sag...@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbast...@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <pal...@sifive.com>
Cc: Alistair Francis <alistair.fran...@wdc.com>
Signed-off-by: Michael Clark <m...@sifive.com>
---
hw/riscv/sifive_plic.c | 36 +++++++++++++++---------------------
include/hw/riscv/sifive_plic.h | 1 -
2 files changed, 15 insertions(+), 22 deletions(-)
diff --git a/hw/riscv/sifive_plic.c b/hw/riscv/sifive_plic.c
index 874de2e..04e39e4 100644
--- a/hw/riscv/sifive_plic.c
+++ b/hw/riscv/sifive_plic.c
@@ -84,33 +84,28 @@ static void sifive_plic_print_state(SiFivePLICState *plic)
static
void sifive_plic_set_pending(SiFivePLICState *plic, int irq, bool pending)
{
- 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;
+ do {
+ old = atomic_read(&plic->pending[word]);
+ new = (old & ~(1 << (irq & 31))) | (-!!pending & (1 << (irq & 31)));
+ } while (atomic_cmpxchg(&plic->pending[word], old, new) != old);
}
static
void sifive_plic_set_claimed(SiFivePLICState *plic, int irq, bool claimed)
{
- 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);
+ uint32_t old, new;
+ do {
+ old = atomic_read(&plic->claimed[word]);
+ new = (old & ~(1 << (irq & 31))) | (-!!claimed & (1 << (irq & 31)));
+ } while (atomic_cmpxchg(&plic->claimed[word], old, new) != old);
}
-static
-int sifive_plic_num_irqs_pending(SiFivePLICState *plic, uint32_t addrid)
+static int sifive_plic_irqs_pending(SiFivePLICState *plic, uint32_t addrid)
{
- int i, j, count = 0;
+ 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 +118,11 @@ 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 +138,7 @@ 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 +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);
diff --git a/include/hw/riscv/sifive_plic.h b/include/hw/riscv/sifive_plic.h
index 11a5a98..ff09a28 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
