Commit 46044f72 authored by Ben Gardon's avatar Ben Gardon Committed by Paolo Bonzini
Browse files

kvm: x86/mmu: Support write protection for nesting in tdp MMU 

To support nested virtualization, KVM will sometimes need to write
protect pages which are part of a shadowed paging structure or are not
writable in the shadowed paging structure. Add a function to write
protect GFN mappings for this purpose.

Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.

This series can be viewed in Gerrit at:
	https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538



Signed-off-by: default avatarBen Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-18-bgardon@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 14881998

arch/x86/kvm/mmu/mmu.c

+4 −0
Original line number Diff line number Diff line
@@ -1299,6 +1299,10 @@ bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm, 
		write_protected |= __rmap_write_protect(kvm, rmap_head, true);

	}



	if (kvm->arch.tdp_mmu_enabled)

		write_protected |=

			kvm_tdp_mmu_write_protect_gfn(kvm, slot, gfn);



	return write_protected;

}

arch/x86/kvm/mmu/tdp_mmu.c

+50 −0
Original line number Diff line number Diff line
@@ -1078,3 +1078,53 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, 
		kvm_mmu_put_root(kvm, root);

	}

}



/*

 * Removes write access on the last level SPTE mapping this GFN and unsets the

 * SPTE_MMU_WRITABLE bit to ensure future writes continue to be intercepted.

 * Returns true if an SPTE was set and a TLB flush is needed.

 */

static bool write_protect_gfn(struct kvm *kvm, struct kvm_mmu_page *root,

			      gfn_t gfn)

{

	struct tdp_iter iter;

	u64 new_spte;

	bool spte_set = false;



	tdp_root_for_each_leaf_pte(iter, root, gfn, gfn + 1) {

		if (!is_writable_pte(iter.old_spte))

			break;



		new_spte = iter.old_spte &

			~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE);



		tdp_mmu_set_spte(kvm, &iter, new_spte);

		spte_set = true;

	}



	return spte_set;

}



/*

 * Removes write access on the last level SPTE mapping this GFN and unsets the

 * SPTE_MMU_WRITABLE bit to ensure future writes continue to be intercepted.

 * Returns true if an SPTE was set and a TLB flush is needed.

 */

bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm,

				   struct kvm_memory_slot *slot, gfn_t gfn)

{

	struct kvm_mmu_page *root;

	int root_as_id;

	bool spte_set = false;



	lockdep_assert_held(&kvm->mmu_lock);

	for_each_tdp_mmu_root(kvm, root) {

		root_as_id = kvm_mmu_page_as_id(root);

		if (root_as_id != slot->as_id)

			continue;



		spte_set |= write_protect_gfn(kvm, root, gfn);

	}

	return spte_set;

}

arch/x86/kvm/mmu/tdp_mmu.h

+3 −0
Original line number Diff line number Diff line
@@ -40,4 +40,7 @@ void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm, 
bool kvm_tdp_mmu_slot_set_dirty(struct kvm *kvm, struct kvm_memory_slot *slot);

void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,

				       const struct kvm_memory_slot *slot);



bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm,

				   struct kvm_memory_slot *slot, gfn_t gfn);

#endif /* __KVM_X86_MMU_TDP_MMU_H */

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