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Diffstat (limited to 'hw/intc/ioapic.c')
-rw-r--r--hw/intc/ioapic.c33
1 files changed, 33 insertions, 0 deletions
diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index 4f42b911a2..273bb0854c 100644
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -255,6 +255,34 @@ ioapic_mem_read(void *opaque, hwaddr addr, unsigned int size)
return val;
}
+/*
+ * This is to satisfy the hack in Linux kernel. One hack of it is to
+ * simulate clearing the Remote IRR bit of IOAPIC entry using the
+ * following:
+ *
+ * "For IO-APIC's with EOI register, we use that to do an explicit EOI.
+ * Otherwise, we simulate the EOI message manually by changing the trigger
+ * mode to edge and then back to level, with RTE being masked during
+ * this."
+ *
+ * (See linux kernel __eoi_ioapic_pin() comment in commit c0205701)
+ *
+ * This is based on the assumption that, Remote IRR bit will be
+ * cleared by IOAPIC hardware when configured as edge-triggered
+ * interrupts.
+ *
+ * Without this, level-triggered interrupts in IR mode might fail to
+ * work correctly.
+ */
+static inline void
+ioapic_fix_edge_remote_irr(uint64_t *entry)
+{
+ if (!(*entry & IOAPIC_LVT_TRIGGER_MODE)) {
+ /* Edge-triggered interrupts, make sure remote IRR is zero */
+ *entry &= ~((uint64_t)IOAPIC_LVT_REMOTE_IRR);
+ }
+}
+
static void
ioapic_mem_write(void *opaque, hwaddr addr, uint64_t val,
unsigned int size)
@@ -281,6 +309,7 @@ ioapic_mem_write(void *opaque, hwaddr addr, uint64_t val,
default:
index = (s->ioregsel - IOAPIC_REG_REDTBL_BASE) >> 1;
if (index >= 0 && index < IOAPIC_NUM_PINS) {
+ uint64_t ro_bits = s->ioredtbl[index] & IOAPIC_RO_BITS;
if (s->ioregsel & 1) {
s->ioredtbl[index] &= 0xffffffff;
s->ioredtbl[index] |= (uint64_t)val << 32;
@@ -288,6 +317,10 @@ ioapic_mem_write(void *opaque, hwaddr addr, uint64_t val,
s->ioredtbl[index] &= ~0xffffffffULL;
s->ioredtbl[index] |= val;
}
+ /* restore RO bits */
+ s->ioredtbl[index] &= IOAPIC_RW_BITS;
+ s->ioredtbl[index] |= ro_bits;
+ ioapic_fix_edge_remote_irr(&s->ioredtbl[index]);
ioapic_service(s);
}
}