KVM: arm64: Add kvm_pgtable_stage2_find_range()

Since the host stage 2 will be identity mapped, and since it will own
most of memory, it would preferable for performance to try and use large
block mappings whenever that is possible. To ease this, introduce a new
helper in the KVM page-table code which allows to search for large
ranges of available IPA space. This will be used in the host memory
abort path to greedily idmap large portion of the PA space.

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-32-qperret@google.com

1 files changed, 29 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index eea2e2b0acaa..e1fed14aee17 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -95,6 +95,16 @@ enum kvm_pgtable_prot {
 #define PAGE_HYP_DEVICE		(PAGE_HYP | KVM_PGTABLE_PROT_DEVICE)
 
 /**
+ * struct kvm_mem_range - Range of Intermediate Physical Addresses
+ * @start:	Start of the range.
+ * @end:	End of the range.
+ */
+struct kvm_mem_range {
+	u64 start;
+	u64 end;
+};
+
+/**
  * enum kvm_pgtable_walk_flags - Flags to control a depth-first page-table walk.
  * @KVM_PGTABLE_WALK_LEAF:		Visit leaf entries, including invalid
  *					entries.
@@ -397,4 +407,23 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size);
 int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
 		     struct kvm_pgtable_walker *walker);
 
+/**
+ * kvm_pgtable_stage2_find_range() - Find a range of Intermediate Physical
+ *				     Addresses with compatible permission
+ *				     attributes.
+ * @pgt:	Page-table structure initialised by kvm_pgtable_stage2_init().
+ * @addr:	Address that must be covered by the range.
+ * @prot:	Protection attributes that the range must be compatible with.
+ * @range:	Range structure used to limit the search space at call time and
+ *		that will hold the result.
+ *
+ * The offset of @addr within a page is ignored. An IPA is compatible with @prot
+ * iff its corresponding stage-2 page-table entry has default ownership and, if
+ * valid, is mapped with protection attributes identical to @prot.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_stage2_find_range(struct kvm_pgtable *pgt, u64 addr,
+				  enum kvm_pgtable_prot prot,
+				  struct kvm_mem_range *range);
 #endif	/* __ARM64_KVM_PGTABLE_H__ */