Merge branch kvm-arm64/pkvm-hyp-sharing into kvmarm-master/next

* kvm-arm64/pkvm-hyp-sharing:
  : .
  : Series from Quentin Perret, implementing HYP page share/unshare:
  :
  : This series implements an unshare hypercall at EL2 in nVHE
  : protected mode, and makes use of it to unmmap guest-specific
  : data-structures from EL2 stage-1 during guest tear-down.
  : Crucially, the implementation of the share and unshare
  : routines use page refcounts in the host kernel to avoid
  : accidentally unmapping data-structures that overlap a common
  : page.
  : [...]
  : .
  KVM: arm64: pkvm: Unshare guest structs during teardown
  KVM: arm64: Expose unshare hypercall to the host
  KVM: arm64: Implement do_unshare() helper for unsharing memory
  KVM: arm64: Implement __pkvm_host_share_hyp() using do_share()
  KVM: arm64: Implement do_share() helper for sharing memory
  KVM: arm64: Introduce wrappers for host and hyp spin lock accessors
  KVM: arm64: Extend pkvm_page_state enumeration to handle absent pages
  KVM: arm64: pkvm: Refcount the pages shared with EL2
  KVM: arm64: Introduce kvm_share_hyp()
  KVM: arm64: Implement kvm_pgtable_hyp_unmap() at EL2
  KVM: arm64: Hook up ->page_count() for hypervisor stage-1 page-table
  KVM: arm64: Fixup hyp stage-1 refcount
  KVM: arm64: Refcount hyp stage-1 pgtable pages
  KVM: arm64: Provide {get,put}_page() stubs for early hyp allocator

Signed-off-by: Marc Zyngier <maz@kernel.org>

1 files changed, 82 insertions, 20 deletions

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index f8ceebe4982e..adc73f8cd24f 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -383,21 +383,6 @@ enum kvm_pgtable_prot kvm_pgtable_hyp_pte_prot(kvm_pte_t pte)
 	return prot;
 }
 
-static bool hyp_pte_needs_update(kvm_pte_t old, kvm_pte_t new)
-{
-	/*
-	 * Tolerate KVM recreating the exact same mapping, or changing software
-	 * bits if the existing mapping was valid.
-	 */
-	if (old == new)
-		return false;
-
-	if (!kvm_pte_valid(old))
-		return true;
-
-	return !WARN_ON((old ^ new) & ~KVM_PTE_LEAF_ATTR_HI_SW);
-}
-
 static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
 				    kvm_pte_t *ptep, struct hyp_map_data *data)
 {
@@ -407,11 +392,16 @@ static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
 	if (!kvm_block_mapping_supported(addr, end, phys, level))
 		return false;
 
+	data->phys += granule;
 	new = kvm_init_valid_leaf_pte(phys, data->attr, level);
-	if (hyp_pte_needs_update(old, new))
-		smp_store_release(ptep, new);
+	if (old == new)
+		return true;
+	if (!kvm_pte_valid(old))
+		data->mm_ops->get_page(ptep);
+	else if (WARN_ON((old ^ new) & ~KVM_PTE_LEAF_ATTR_HI_SW))
+		return false;
 
-	data->phys += granule;
+	smp_store_release(ptep, new);
 	return true;
 }
 
@@ -433,6 +423,7 @@ static int hyp_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 		return -ENOMEM;
 
 	kvm_set_table_pte(ptep, childp, mm_ops);
+	mm_ops->get_page(ptep);
 	return 0;
 }
 
@@ -460,6 +451,69 @@ int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
 	return ret;
 }
 
+struct hyp_unmap_data {
+	u64				unmapped;
+	struct kvm_pgtable_mm_ops	*mm_ops;
+};
+
+static int hyp_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+			    enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+	kvm_pte_t pte = *ptep, *childp = NULL;
+	u64 granule = kvm_granule_size(level);
+	struct hyp_unmap_data *data = arg;
+	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+
+	if (!kvm_pte_valid(pte))
+		return -EINVAL;
+
+	if (kvm_pte_table(pte, level)) {
+		childp = kvm_pte_follow(pte, mm_ops);
+
+		if (mm_ops->page_count(childp) != 1)
+			return 0;
+
+		kvm_clear_pte(ptep);
+		dsb(ishst);
+		__tlbi_level(vae2is, __TLBI_VADDR(addr, 0), level);
+	} else {
+		if (end - addr < granule)
+			return -EINVAL;
+
+		kvm_clear_pte(ptep);
+		dsb(ishst);
+		__tlbi_level(vale2is, __TLBI_VADDR(addr, 0), level);
+		data->unmapped += granule;
+	}
+
+	dsb(ish);
+	isb();
+	mm_ops->put_page(ptep);
+
+	if (childp)
+		mm_ops->put_page(childp);
+
+	return 0;
+}
+
+u64 kvm_pgtable_hyp_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size)
+{
+	struct hyp_unmap_data unmap_data = {
+		.mm_ops	= pgt->mm_ops,
+	};
+	struct kvm_pgtable_walker walker = {
+		.cb	= hyp_unmap_walker,
+		.arg	= &unmap_data,
+		.flags	= KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
+	};
+
+	if (!pgt->mm_ops->page_count)
+		return 0;
+
+	kvm_pgtable_walk(pgt, addr, size, &walker);
+	return unmap_data.unmapped;
+}
+
 int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits,
 			 struct kvm_pgtable_mm_ops *mm_ops)
 {
@@ -482,8 +536,16 @@ static int hyp_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 			   enum kvm_pgtable_walk_flags flag, void * const arg)
 {
 	struct kvm_pgtable_mm_ops *mm_ops = arg;
+	kvm_pte_t pte = *ptep;
+
+	if (!kvm_pte_valid(pte))
+		return 0;
+
+	mm_ops->put_page(ptep);
+
+	if (kvm_pte_table(pte, level))
+		mm_ops->put_page(kvm_pte_follow(pte, mm_ops));
 
-	mm_ops->put_page((void *)kvm_pte_follow(*ptep, mm_ops));
 	return 0;
 }
 
@@ -491,7 +553,7 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
 {
 	struct kvm_pgtable_walker walker = {
 		.cb	= hyp_free_walker,
-		.flags	= KVM_PGTABLE_WALK_TABLE_POST,
+		.flags	= KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
 		.arg	= pgt->mm_ops,
 	};