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KVM: use separate generations for each address space

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This will make it easier to support multiple address spaces in
kvm_gfn_to_hva_cache_init.  Instead of having to check the address
space id, we can keep on checking just the generation number.

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-02-03 20:44:51 -08:00
parent 5a2d4365d2
commit 4bd518f159
1 changed files with 16 additions and 8 deletions
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24
virt/kvm/kvm_main.c
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@ -506,11 +506,6 @@ static struct kvm_memslots *kvm_alloc_memslots(void)
if (!slots)
return NULL;
/*
* Init kvm generation close to the maximum to easily test the
* code of handling generation number wrap-around.
*/
slots->generation = -150;
for (i = 0; i < KVM_MEM_SLOTS_NUM; i++)
slots->id_to_index[i] = slots->memslots[i].id = i;
@ -641,9 +636,16 @@ static struct kvm *kvm_create_vm(unsigned long type)
r = -ENOMEM;
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
kvm->memslots[i] = kvm_alloc_memslots();
if (!kvm->memslots[i])
struct kvm_memslots *slots = kvm_alloc_memslots();
if (!slots)
goto out_err_no_srcu;
/*
* Generations must be different for each address space.
* Init kvm generation close to the maximum to easily test the
* code of handling generation number wrap-around.
*/
slots->generation = i * 2 - 150;
rcu_assign_pointer(kvm->memslots[i], slots);
}
if (init_srcu_struct(&kvm->srcu))
@ -870,8 +872,14 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
* Increment the new memslot generation a second time. This prevents
* vm exits that race with memslot updates from caching a memslot
* generation that will (potentially) be valid forever.
*
* Generations must be unique even across address spaces. We do not need
* a global counter for that, instead the generation space is evenly split
* across address spaces. For example, with two address spaces, address
* space 0 will use generations 0, 4, 8, ... while * address space 1 will
* use generations 2, 6, 10, 14, ...
*/
slots->generation++;
slots->generation += KVM_ADDRESS_SPACE_NUM * 2 - 1;
kvm_arch_memslots_updated(kvm, slots);