Commit 7b7e1ab6 authored by David Matlack's avatar David Matlack Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Consolidate logic to atomically install a new TDP MMU page table 



Consolidate the logic to atomically replace an SPTE with an SPTE that
points to a new page table into a single helper function. This will be
used in a follow-up commit to split huge pages, which involves replacing
each huge page SPTE with an SPTE that points to a page table.

Opportunistically drop the call to trace_kvm_mmu_get_page() in
kvm_tdp_mmu_map() since it is redundant with the identical tracepoint in
tdp_mmu_alloc_sp().

No functional change intended.

Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarDavid Matlack <dmatlack@google.com>
Message-Id: <20220119230739.2234394-8-dmatlack@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0f53dfa3

arch/x86/kvm/mmu/tdp_mmu.c

+36 −32
Original line number Diff line number Diff line
@@ -268,24 +268,6 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn, 
	}

}



/**

 * tdp_mmu_link_sp() - Add a new shadow page to the list of used pages

 *

 * @kvm: kvm instance

 * @sp: the new page

 * @account_nx: This page replaces a NX large page and should be marked for

 *		eventual reclaim.

 */

static void tdp_mmu_link_sp(struct kvm *kvm, struct kvm_mmu_page *sp,

			    bool account_nx)

{

	spin_lock(&kvm->arch.tdp_mmu_pages_lock);

	list_add(&sp->link, &kvm->arch.tdp_mmu_pages);

	if (account_nx)

		account_huge_nx_page(kvm, sp);

	spin_unlock(&kvm->arch.tdp_mmu_pages_lock);

}



/**

 * tdp_mmu_unlink_sp() - Remove a shadow page from the list of used pages

 *
@@ -979,6 +961,38 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, 
	return ret;

}



/*

 * tdp_mmu_link_sp_atomic - Atomically replace the given spte with an spte

 * pointing to the provided page table.

 *

 * @kvm: kvm instance

 * @iter: a tdp_iter instance currently on the SPTE that should be set

 * @sp: The new TDP page table to install.

 * @account_nx: True if this page table is being installed to split a

 *              non-executable huge page.

 *

 * Returns: 0 if the new page table was installed. Non-0 if the page table

 *          could not be installed (e.g. the atomic compare-exchange failed).

 */

static int tdp_mmu_link_sp_atomic(struct kvm *kvm, struct tdp_iter *iter,

				  struct kvm_mmu_page *sp, bool account_nx)

{

	u64 spte = make_nonleaf_spte(sp->spt, !shadow_accessed_mask);

	int ret;



	ret = tdp_mmu_set_spte_atomic(kvm, iter, spte);

	if (ret)

		return ret;



	spin_lock(&kvm->arch.tdp_mmu_pages_lock);

	list_add(&sp->link, &kvm->arch.tdp_mmu_pages);

	if (account_nx)

		account_huge_nx_page(kvm, sp);

	spin_unlock(&kvm->arch.tdp_mmu_pages_lock);



	return 0;

}



/*

 * Handle a TDP page fault (NPT/EPT violation/misconfiguration) by installing

 * page tables and SPTEs to translate the faulting guest physical address.
@@ -988,8 +1002,6 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) 
	struct kvm_mmu *mmu = vcpu->arch.mmu;

	struct tdp_iter iter;

	struct kvm_mmu_page *sp;

	u64 *child_pt;

	u64 new_spte;

	int ret;



	kvm_mmu_hugepage_adjust(vcpu, fault);
@@ -1024,6 +1036,9 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) 
		}



		if (!is_shadow_present_pte(iter.old_spte)) {

			bool account_nx = fault->huge_page_disallowed &&

					  fault->req_level >= iter.level;



			/*

			 * If SPTE has been frozen by another thread, just

			 * give up and retry, avoiding unnecessary page table
@@ -1033,18 +1048,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) 
				break;



			sp = tdp_mmu_alloc_sp(vcpu, iter.gfn, iter.level - 1);

			child_pt = sp->spt;



			new_spte = make_nonleaf_spte(child_pt,

						     !shadow_accessed_mask);



			if (!tdp_mmu_set_spte_atomic(vcpu->kvm, &iter, new_spte)) {

				tdp_mmu_link_sp(vcpu->kvm, sp,

						fault->huge_page_disallowed &&

						fault->req_level >= iter.level);



				trace_kvm_mmu_get_page(sp, true);

			} else {

			if (tdp_mmu_link_sp_atomic(vcpu->kvm, &iter, sp, account_nx)) {

				tdp_mmu_free_sp(sp);

				break;

			}