Commit 748e52b9 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Allocate pae_root and lm_root pages in dedicated helper 



Move the on-demand allocation of the pae_root and lm_root pages, used by
nested NPT for 32-bit L1s, into a separate helper.  This will allow a
future patch to hold mmu_lock while allocating the non-special roots so
that make_mmu_pages_available() can be checked once at the start of root
allocation, and thus avoid having to deal with failure in the middle of
root allocation.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-6-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent ba0a194f

arch/x86/kvm/mmu/mmu.c

+54 −30
Original line number Diff line number Diff line
@@ -3314,38 +3314,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) 
	 * the shadow page table may be a PAE or a long mode page table.

	 */

	pm_mask = PT_PRESENT_MASK;

	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)

	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL) {

		pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;



	/*

	 * When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP

	 * tables are allocated and initialized at root creation as there is no

	 * equivalent level in the guest's NPT to shadow.  Allocate the tables

	 * on demand, as running a 32-bit L1 VMM is very rare.  Unlike 32-bit

	 * NPT, the PDP table doesn't need to be in low mem.  Preallocate the

	 * pages so that the PAE roots aren't leaked on failure.

	 */

	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL &&

	    (!mmu->pae_root || !mmu->lm_root)) {

		u64 *lm_root, *pae_root;



		if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->lm_root))

			return -EIO;



		pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

		if (!pae_root)

			return -ENOMEM;



		lm_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

		if (!lm_root) {

			free_page((unsigned long)pae_root);

			return -ENOMEM;

		}



		mmu->pae_root = pae_root;

		mmu->lm_root = lm_root;



		lm_root[0] = __pa(mmu->pae_root) | pm_mask;

		mmu->lm_root[0] = __pa(mmu->pae_root) | pm_mask;

	}



	for (i = 0; i < 4; ++i) {
@@ -3379,6 +3351,55 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) 
	return 0;

}



static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)

{

	struct kvm_mmu *mmu = vcpu->arch.mmu;

	u64 *lm_root, *pae_root;



	/*

	 * When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP

	 * tables are allocated and initialized at root creation as there is no

	 * equivalent level in the guest's NPT to shadow.  Allocate the tables

	 * on demand, as running a 32-bit L1 VMM on 64-bit KVM is very rare.

	 */

	if (mmu->direct_map || mmu->root_level >= PT64_ROOT_4LEVEL ||

	    mmu->shadow_root_level < PT64_ROOT_4LEVEL)

		return 0;



	/*

	 * This mess only works with 4-level paging and needs to be updated to

	 * work with 5-level paging.

	 */

	if (WARN_ON_ONCE(mmu->shadow_root_level != PT64_ROOT_4LEVEL))

		return -EIO;



	if (mmu->pae_root && mmu->lm_root)

		return 0;



	/*

	 * The special roots should always be allocated in concert.  Yell and

	 * bail if KVM ends up in a state where only one of the roots is valid.

	 */

	if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->lm_root))

		return -EIO;



	/* Unlike 32-bit NPT, the PDP table doesn't need to be in low mem. */

	pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

	if (!pae_root)

		return -ENOMEM;



	lm_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

	if (!lm_root) {

		free_page((unsigned long)pae_root);

		return -ENOMEM;

	}



	mmu->pae_root = pae_root;

	mmu->lm_root = lm_root;



	return 0;

}



static int mmu_alloc_roots(struct kvm_vcpu *vcpu)

{

	if (vcpu->arch.mmu->direct_map)
@@ -4812,6 +4833,9 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu) 
	int r;



	r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->direct_map);

	if (r)

		goto out;

	r = mmu_alloc_special_roots(vcpu);

	if (r)

		goto out;

	r = mmu_alloc_roots(vcpu);