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memory_region_present: return false if address is not found in child MemoryRegion

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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>
This commit is contained in:
Igor Mammedov 2014-02-06 11:24:33 +01:00 committed by Michael S. Tsirkin
parent ddfa83ea06
commit 8e46bbf362
2 changed files with 4 additions and 4 deletions
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6
include/exec/memory.h
View file

@ -836,13 +836,13 @@ void memory_region_set_alias_offset(MemoryRegion *mr,
hwaddr offset);
/**
* memory_region_present: translate an address/size relative to a
* MemoryRegion into a #MemoryRegionSection.
* memory_region_present: checks if an address relative to a @parent
* translates into #MemoryRegion within @parent
*
* Answer whether a #MemoryRegion within @parent covers the address
* @addr.
*
* @parent: a MemoryRegion within which @addr is a relative address
* @parent: a #MemoryRegion within which @addr is a relative address
* @addr: the area within @parent to be searched
*/
bool memory_region_present(MemoryRegion *parent, hwaddr addr);

2
memory.c
View file

@ -1562,7 +1562,7 @@ static FlatRange *flatview_lookup(FlatView *view, AddrRange addr)
bool memory_region_present(MemoryRegion *parent, hwaddr addr)
{
MemoryRegion *mr = memory_region_find(parent, addr, 1).mr;
if (!mr) {
if (!mr || (mr == parent)) {
return false;
}
memory_region_unref(mr);