KVM: Allow browsing memslots with mmu_lock
This allows reading memslots with only the mmu_lock hold for mmu
notifiers that runs in atomic context and with mmu_lock held.
Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a845890..3735212 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -375,7 +375,15 @@
memset(new.rmap, 0, npages * sizeof(*new.rmap));
new.user_alloc = user_alloc;
- new.userspace_addr = mem->userspace_addr;
+ /*
+ * hva_to_rmmap() serialzies with the mmu_lock and to be
+ * safe it has to ignore memslots with !user_alloc &&
+ * !userspace_addr.
+ */
+ if (user_alloc)
+ new.userspace_addr = mem->userspace_addr;
+ else
+ new.userspace_addr = 0;
}
if (npages && !new.lpage_info) {
int largepages = npages / KVM_PAGES_PER_HPAGE;
@@ -408,17 +416,21 @@
}
#endif /* not defined CONFIG_S390 */
- if (mem->slot >= kvm->nmemslots)
- kvm->nmemslots = mem->slot + 1;
-
if (!npages)
kvm_arch_flush_shadow(kvm);
+ spin_lock(&kvm->mmu_lock);
+ if (mem->slot >= kvm->nmemslots)
+ kvm->nmemslots = mem->slot + 1;
+
*memslot = new;
+ spin_unlock(&kvm->mmu_lock);
r = kvm_arch_set_memory_region(kvm, mem, old, user_alloc);
if (r) {
+ spin_lock(&kvm->mmu_lock);
*memslot = old;
+ spin_unlock(&kvm->mmu_lock);
goto out_free;
}