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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>
This commit is contained in:
Andrea Arcangeli 2008-07-25 16:32:03 +02:00 committed by Avi Kivity
parent a1708ce8a3
commit 604b38ac03
2 changed files with 30 additions and 11 deletions
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21
arch/x86/kvm/x86.c
View File

@ -3974,16 +3974,23 @@ int kvm_arch_set_memory_region(struct kvm *kvm,
*/
if (!user_alloc) {
if (npages && !old.rmap) {
unsigned long userspace_addr;
down_write(&current->mm->mmap_sem);
memslot->userspace_addr = do_mmap(NULL, 0,
npages * PAGE_SIZE,
PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS,
0);
userspace_addr = do_mmap(NULL, 0,
npages * PAGE_SIZE,
PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS,
0);
up_write(&current->mm->mmap_sem);
if (IS_ERR((void *)memslot->userspace_addr))
return PTR_ERR((void *)memslot->userspace_addr);
if (IS_ERR((void *)userspace_addr))
return PTR_ERR((void *)userspace_addr);
/* set userspace_addr atomically for kvm_hva_to_rmapp */
spin_lock(&kvm->mmu_lock);
memslot->userspace_addr = userspace_addr;
spin_unlock(&kvm->mmu_lock);
} else {
if (!old.user_alloc && old.rmap) {
int ret;

20
virt/kvm/kvm_main.c
View File

@ -375,7 +375,15 @@ int __kvm_set_memory_region(struct kvm *kvm,
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 @@ int __kvm_set_memory_region(struct kvm *kvm,
}
#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;
}