exec: Do not resolve subpage in mru_section
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>
diff --git a/exec.c b/exec.c
index 97a24a8..3bb9fcf 100644
--- a/exec.c
+++ b/exec.c
@@ -410,22 +410,16 @@
{
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;
}