Windows XP shows COM2 port as non functional in
"Device Manager" although no COM2 port backing device
is present in QEMU.
This regression is really due to
3bb28b7208b349e7a1b326e3c6ef9efac1d462bf?
memory: Provide separate handling of unassigned io ports accesses
That is caused by the fact that QEMU reports to
OSPM that device is present by setting 5th bit in
PII4XPM.pci_conf[0x67] register when COM2 doesn't
exist.
It happens due to memory_region_present(io_as, 0x2f8)
returning false positive since 0x2f8 address eventually
translates into catchall io_as address space.
Fix memory_region_present(parent, addr) by returning
true only if addr maps into a MemoryRegion within
parent (excluding parent itself), to match its
doc comment.
While at it fix copy/paste error in
memory_region_present() doc comment.
Note: this is a temporary hack: we really need better handling for
unassigned regions, we should avoid fallback regions since they are bad
for performance (breaking radix tree assumption that the data structure
is sparsely populated); for memory we need to fix this to implement PCI
master abort properly, anyway.
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
8e46bbf362