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kvm: Fix memory slot generation updates 

Previous patch "kvm: Minor memory slot optimization" (b7f69c555c)
overlooked the generation field of the memory slots.  Re-using the
original memory slots left us with with two slightly different memory
slots with the same generation.  To fix this, make update_memslots()
take a new parameter to specify the last generation.  This also makes
generation management more explicit to avoid such problems in the future.

Reported-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Alex Williamson 2012-12-21 08:20:16 -07:00 committed by Gleb Natapov
parent 871a069db9
commit 116c14c019
2 changed files with 7 additions and 5 deletions
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3
include/linux/kvm_host.h
View File

@ -428,7 +428,8 @@ void kvm_exit(void);
void kvm_get_kvm(struct kvm *kvm);
void kvm_put_kvm(struct kvm *kvm);
void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new);
void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new,
u64 last_generation);
static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm)
{

9
virt/kvm/kvm_main.c
View File

@ -672,7 +672,8 @@ static void sort_memslots(struct kvm_memslots *slots)
slots->id_to_index[slots->memslots[i].id] = i;
}
void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new)
void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new,
u64 last_generation)
{
if (new) {
int id = new->id;
@ -684,7 +685,7 @@ void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new)
sort_memslots(slots);
}
slots->generation++;
slots->generation = last_generation + 1;
}
static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
@ -819,7 +820,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
slot = id_to_memslot(slots, mem->slot);
slot->flags |= KVM_MEMSLOT_INVALID;
update_memslots(slots, NULL);
update_memslots(slots, NULL, kvm->memslots->generation);
old_memslots = kvm->memslots;
rcu_assign_pointer(kvm->memslots, slots);
@ -867,7 +868,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
memset(&new.arch, 0, sizeof(new.arch));
}
update_memslots(slots, &new);
update_memslots(slots, &new, kvm->memslots->generation);
old_memslots = kvm->memslots;
rcu_assign_pointer(kvm->memslots, slots);
synchronize_srcu_expedited(&kvm->srcu);