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Commit 604b38ac authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Avi Kivity
Browse files

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: default avatarAndrea Arcangeli <andrea@qumranet.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent a1708ce8

arch/x86/kvm/x86.c

+14 −7
Original line number Diff line number Diff line
@@ -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,

			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;

virt/kvm/kvm_main.c

+16 −4
Original line number Diff line number Diff line
@@ -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;

		/*

		 * 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;

	}