[PATCH 4/8] KVM: arm64: Pass walk flags to kvm_pgtable_get_leaf()

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

From: Jack Thomson <jackabt@amazon.com>

Allow callers of kvm_pgtable_get_leaf() to specify the page-table walk
flags, in preparation for performing walks under the MMU read lock.

Reading a stage-2 leaf while only holding the read lock requires
KVM_PGTABLE_WALK_SHARED: parallel faults (which also only hold the read
lock) can unlink table pages and free them via RCU, so the walker must
be inside an RCU read-side critical section, which the shared walk flag
provides via kvm_pgtable_walk_begin().

All existing callers either hold the write lock, walk with interrupts
disabled, or run at hyp where shared walks are rejected; they keep the
current behaviour by passing no flags.

No functional change intended.

Signed-off-by: Jack Thomson <jackabt@amazon.com>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 arch/arm64/include/asm/kvm_pgtable.h  |  5 ++++-
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 10 +++++-----
 arch/arm64/kvm/hyp/pgtable.c          |  5 +++--
 arch/arm64/kvm/mmu.c                  |  2 +-
 arch/arm64/kvm/nested.c               |  2 +-
 5 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 41a8687938eb..d0167f7dfbee 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -859,6 +859,8 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
  * @addr:	Input address for the start of the walk.
  * @ptep:	Pointer to storage for the retrieved PTE.
  * @level:	Pointer to storage for the level of the retrieved PTE.
+ * @flags:	Flags to control the page-table walk
+ *		(see struct kvm_pgtable_visit_ctx).
  *
  * The offset of @addr within a page is ignored.
  *
@@ -869,7 +871,8 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
  * Return: 0 on success, negative error code on failure.
  */
 int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
-			 kvm_pte_t *ptep, s8 *level);
+			 kvm_pte_t *ptep, s8 *level,
+			 enum kvm_pgtable_walk_flags flags);
 
 /**
  * kvm_pgtable_stage2_pte_prot() - Retrieve the protection attributes of a
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 39aa8911f62c..23a57312b981 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -532,7 +532,7 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range)
 	int ret;
 
 	hyp_assert_lock_held(&host_mmu.lock);
-	ret = kvm_pgtable_get_leaf(&host_mmu.pgt, addr, &pte, &level);
+	ret = kvm_pgtable_get_leaf(&host_mmu.pgt, addr, &pte, &level, 0);
 	if (ret)
 		return ret;
 
@@ -910,7 +910,7 @@ static int get_valid_guest_pte(struct pkvm_hyp_vm *vm, u64 ipa, kvm_pte_t *ptep,
 	s8 level;
 	int ret;
 
-	ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level);
+	ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level, 0);
 	if (ret)
 		return ret;
 	if (guest_pte_is_poisoned(pte))
@@ -959,7 +959,7 @@ int __pkvm_vcpu_in_poison_fault(struct pkvm_hyp_vcpu *hyp_vcpu)
 	ipa |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(&hyp_vcpu->vcpu));
 
 	guest_lock_component(vm);
-	ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level);
+	ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level, 0);
 	if (ret)
 		goto unlock;
 
@@ -1315,7 +1315,7 @@ static int host_stage2_get_guest_info(phys_addr_t phys, struct pkvm_hyp_vm **vm,
 		return -EPERM;
 	}
 
-	ret = kvm_pgtable_get_leaf(&host_mmu.pgt, phys, &pte, &level);
+	ret = kvm_pgtable_get_leaf(&host_mmu.pgt, phys, &pte, &level, 0);
 	if (ret)
 		return ret;
 
@@ -1544,7 +1544,7 @@ static int __check_host_shared_guest(struct pkvm_hyp_vm *vm, u64 *__phys, u64 ip
 	s8 level;
 	int ret;
 
-	ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level);
+	ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level, 0);
 	if (ret)
 		return ret;
 	if (!kvm_pte_valid(pte))
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index b74dd5ce1efd..347eec3957d6 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -298,12 +298,13 @@ static int leaf_walker(const struct kvm_pgtable_visit_ctx *ctx,
 }
 
 int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
-			 kvm_pte_t *ptep, s8 *level)
+			 kvm_pte_t *ptep, s8 *level,
+			 enum kvm_pgtable_walk_flags flags)
 {
 	struct leaf_walk_data data;
 	struct kvm_pgtable_walker walker = {
 		.cb	= leaf_walker,
-		.flags	= KVM_PGTABLE_WALK_LEAF,
+		.flags	= flags | KVM_PGTABLE_WALK_LEAF,
 		.arg	= &data,
 	};
 	int ret;
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index da15da4e40e6..16299004f229 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -866,7 +866,7 @@ static int get_user_mapping_size(struct kvm *kvm, u64 addr)
 	 * IPI-ing threads).
 	 */
 	local_irq_save(flags);
-	ret = kvm_pgtable_get_leaf(&pgt, addr, &pte, &level);
+	ret = kvm_pgtable_get_leaf(&pgt, addr, &pte, &level, 0);
 	local_irq_restore(flags);
 
 	if (ret)
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 17123f0b6dab..3488d5ad225b 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -654,7 +654,7 @@ static u8 get_guest_mapping_ttl(struct kvm_s2_mmu *mmu, u64 addr)
 		return 0;
 
 	tmp &= ~(sz - 1);
-	if (kvm_pgtable_get_leaf(mmu->pgt, tmp, &pte, NULL))
+	if (kvm_pgtable_get_leaf(mmu->pgt, tmp, &pte, NULL, 0))
 		goto again;
 	if (!(pte & PTE_VALID))
 		goto again;

-- 
2.55.0