qemu: x86: ignore ioapic polarity

Both QEMU and KVM have already accumulated a significant number of
optimizations based on the hard-coded assumption that ioapic polarity
will always use the ActiveHigh convention, where the logical and
physical states of level-triggered irq lines always match (i.e.,
active(asserted) == high == 1, inactive == low == 0). QEMU guests
are expected to follow directions given via ACPI and configure the
ioapic with polarity 0 (ActiveHigh). However, even when misbehaving
guests (e.g. OS X <= 10.9) set the ioapic polarity to 1 (ActiveLow),
QEMU will still use the ActiveHigh signaling convention when
interfacing with the emulated ioapic.

This patch modifies the emulated ioapic to completely ignore polarity
as set by the guest OS, enabling misbehaving guests to work alongside
those which comply with the ActiveHigh polarity specified by QEMU's
ACPI tables.

Signed-off-by: Gabriel L. Somlo <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>

diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index 652dd47a1c1ec2658f5783274dcc30acff985799..b527932382677363299bcb8668b9f950a103bcf8 100644 (file)
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -93,9 +93,6 @@ static void ioapic_set_irq(void *opaque, int vector, int level)
         uint32_t mask = 1 << vector;
         uint64_t entry = s->ioredtbl[vector];
 
-        if (entry & (1 << IOAPIC_LVT_POLARITY_SHIFT)) {
-            level = !level;
-        }
         if (((entry >> IOAPIC_LVT_TRIGGER_MODE_SHIFT) & 1) ==
             IOAPIC_TRIGGER_LEVEL) {
             /* level triggered */