Commit 594bef79 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86/mmu: do not consult levels when freeing roots 



Right now, PGD caching requires a complicated dance of first computing
the MMU role and passing it to __kvm_mmu_new_pgd(), and then separately calling
kvm_init_mmu().

Part of this is due to kvm_mmu_free_roots using mmu->root_level and
mmu->shadow_root_level to distinguish whether the page table uses a single
root or 4 PAE roots.  Because kvm_init_mmu() can overwrite mmu->root_level,
kvm_mmu_free_roots() must be called before kvm_init_mmu().

However, even after kvm_init_mmu() there is a way to detect whether the
page table may hold PAE roots, as root.hpa isn't backed by a shadow when
it points at PAE roots.  Using this method results in simpler code, and
is one less obstacle in moving all calls to __kvm_mmu_new_pgd() after the
MMU has been initialized.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b9e5603c

arch/x86/kvm/mmu/mmu.c

+6 −4
Original line number Diff line number Diff line
@@ -3224,12 +3224,15 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, 
	struct kvm *kvm = vcpu->kvm;

	int i;

	LIST_HEAD(invalid_list);

	bool free_active_root = roots_to_free & KVM_MMU_ROOT_CURRENT;

	bool free_active_root;



	BUILD_BUG_ON(KVM_MMU_NUM_PREV_ROOTS >= BITS_PER_LONG);



	/* Before acquiring the MMU lock, see if we need to do any real work. */

	if (!(free_active_root && VALID_PAGE(mmu->root.hpa))) {

	free_active_root = (roots_to_free & KVM_MMU_ROOT_CURRENT)

		&& VALID_PAGE(mmu->root.hpa);



	if (!free_active_root) {

		for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)

			if ((roots_to_free & KVM_MMU_ROOT_PREVIOUS(i)) &&

			    VALID_PAGE(mmu->prev_roots[i].hpa))
@@ -3247,8 +3250,7 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, 
					   &invalid_list);



	if (free_active_root) {

		if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL &&

		    (mmu->root_level >= PT64_ROOT_4LEVEL || mmu->direct_map)) {

		if (to_shadow_page(mmu->root.hpa)) {

			mmu_free_root_page(kvm, &mmu->root.hpa, &invalid_list);

		} else if (mmu->pae_root) {

			for (i = 0; i < 4; ++i) {