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exec: Do not resolve subpage in mru_section

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This fixes a crash caused by picking the wrong memory region in
address_space_lookup_region seen with client code accessing a device
model that uses alias memory regions.  The expensive part of
address_space_lookup_region anyway is phys_page_find; performance-wise
it is okay to repeat the subsequent subpage lookup.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-Id: <20171114225941.072707456B5@zero.eik.bme.hu>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-11-15 15:11:03 +01:00
parent 26a5db322b
commit 07c114bbf3
1 changed files with 3 additions and 9 deletions
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12
exec.c
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@ -410,22 +410,16 @@ static MemoryRegionSection *address_space_lookup_region(AddressSpaceDispatch *d,
{
MemoryRegionSection *section = atomic_read(&d->mru_section);
subpage_t *subpage;
bool update;
if (section && section != &d->map.sections[PHYS_SECTION_UNASSIGNED] &&
section_covers_addr(section, addr)) {
update = false;
} else {
if (!section || section == &d->map.sections[PHYS_SECTION_UNASSIGNED] ||
!section_covers_addr(section, addr)) {
section = phys_page_find(d, addr);
update = true;
atomic_set(&d->mru_section, section);
}
if (resolve_subpage && section->mr->subpage) {
subpage = container_of(section->mr, subpage_t, iomem);
section = &d->map.sections[subpage->sub_section[SUBPAGE_IDX(addr)]];
}
if (update) {
atomic_set(&d->mru_section, section);
}
return section;
}