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qemu: x86: ignore ioapic polarity

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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 <somlo@cmu.edu>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Gabriel L. Somlo 2014-02-28 13:57:19 -05:00 committed by Michael S. Tsirkin
parent f1b7e0e498
commit 220c8ed536
1 changed files with 0 additions and 3 deletions
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3
hw/intc/ioapic.c
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@ -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 */