1 files changed, 118 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h
new file mode 100644
index 000000000..f0af385c5
--- /dev/null
+++ b/arch/x86/kvm/mmu/tdp_iter.h
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef __KVM_X86_MMU_TDP_ITER_H
+#define __KVM_X86_MMU_TDP_ITER_H
+
+#include <linux/kvm_host.h>
+
+#include "mmu.h"
+#include "spte.h"
+
+/*
+ * TDP MMU SPTEs are RCU protected to allow paging structures (non-leaf SPTEs)
+ * to be zapped while holding mmu_lock for read, and to allow TLB flushes to be
+ * batched without having to collect the list of zapped SPs.  Flows that can
+ * remove SPs must service pending TLB flushes prior to dropping RCU protection.
+ */
+static inline u64 kvm_tdp_mmu_read_spte(tdp_ptep_t sptep)
+{
+	return READ_ONCE(*rcu_dereference(sptep));
+}
+
+static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte)
+{
+	return xchg(rcu_dereference(sptep), new_spte);
+}
+
+static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte)
+{
+	WRITE_ONCE(*rcu_dereference(sptep), new_spte);
+}
+
+static inline u64 kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 old_spte,
+					 u64 new_spte, int level)
+{
+	/*
+	 * Atomically write the SPTE if it is a shadow-present, leaf SPTE with
+	 * volatile bits, i.e. has bits that can be set outside of mmu_lock.
+	 * The Writable bit can be set by KVM's fast page fault handler, and
+	 * Accessed and Dirty bits can be set by the CPU.
+	 *
+	 * Note, non-leaf SPTEs do have Accessed bits and those bits are
+	 * technically volatile, but KVM doesn't consume the Accessed bit of
+	 * non-leaf SPTEs, i.e. KVM doesn't care if it clobbers the bit.  This
+	 * logic needs to be reassessed if KVM were to use non-leaf Accessed
+	 * bits, e.g. to skip stepping down into child SPTEs when aging SPTEs.
+	 */
+	if (is_shadow_present_pte(old_spte) && is_last_spte(old_spte, level) &&
+	    spte_has_volatile_bits(old_spte))
+		return kvm_tdp_mmu_write_spte_atomic(sptep, new_spte);
+
+	__kvm_tdp_mmu_write_spte(sptep, new_spte);
+	return old_spte;
+}
+
+/*
+ * A TDP iterator performs a pre-order walk over a TDP paging structure.
+ */
+struct tdp_iter {
+	/*
+	 * The iterator will traverse the paging structure towards the mapping
+	 * for this GFN.
+	 */
+	gfn_t next_last_level_gfn;
+	/*
+	 * The next_last_level_gfn at the time when the thread last
+	 * yielded. Only yielding when the next_last_level_gfn !=
+	 * yielded_gfn helps ensure forward progress.
+	 */
+	gfn_t yielded_gfn;
+	/* Pointers to the page tables traversed to reach the current SPTE */
+	tdp_ptep_t pt_path[PT64_ROOT_MAX_LEVEL];
+	/* A pointer to the current SPTE */
+	tdp_ptep_t sptep;
+	/* The lowest GFN mapped by the current SPTE */
+	gfn_t gfn;
+	/* The level of the root page given to the iterator */
+	int root_level;
+	/* The lowest level the iterator should traverse to */
+	int min_level;
+	/* The iterator's current level within the paging structure */
+	int level;
+	/* The address space ID, i.e. SMM vs. regular. */
+	int as_id;
+	/* A snapshot of the value at sptep */
+	u64 old_spte;
+	/*
+	 * Whether the iterator has a valid state. This will be false if the
+	 * iterator walks off the end of the paging structure.
+	 */
+	bool valid;
+	/*
+	 * True if KVM dropped mmu_lock and yielded in the middle of a walk, in
+	 * which case tdp_iter_next() needs to restart the walk at the root
+	 * level instead of advancing to the next entry.
+	 */
+	bool yielded;
+};
+
+/*
+ * Iterates over every SPTE mapping the GFN range [start, end) in a
+ * preorder traversal.
+ */
+#define for_each_tdp_pte_min_level(iter, root, min_level, start, end) \
+	for (tdp_iter_start(&iter, root, min_level, start); \
+	     iter.valid && iter.gfn < end;		     \
+	     tdp_iter_next(&iter))
+
+#define for_each_tdp_pte(iter, root, start, end) \
+	for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end)
+
+tdp_ptep_t spte_to_child_pt(u64 pte, int level);
+
+void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root,
+		    int min_level, gfn_t next_last_level_gfn);
+void tdp_iter_next(struct tdp_iter *iter);
+void tdp_iter_restart(struct tdp_iter *iter);
+
+#endif /* __KVM_X86_MMU_TDP_ITER_H */