[PATCH v3 16/21] KVM: arm64: Enable retrieving protections attributes of PTEs

Quentin Perret
2021-07-29T13:29:43Z

Introduce helper functions in the KVM stage-2 and stage-1 page-table
manipulation library allowing to retrieve the enum kvm_pgtable_prot of a
PTE. This will be useful to implement custom walkers outside of
pgtable.c.

Signed-off-by: Quentin Perret <qperret@google.com>
---
arch/arm64/include/asm/kvm_pgtable.h | 20 +++++++++++++++
arch/arm64/kvm/hyp/pgtable.c | 37 ++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index d5ca9b6ce241..7ff9f52239ba 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -505,4 +505,24 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
*/
int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
kvm_pte_t *ptep, u32 *level);
+
+/**
+ * kvm_pgtable_stage2_pte_prot() - Retrieve the protection attributes of a
+ * stage-2 Page-Table Entry.
+ * @pte: Page-table entry
+ *
+ * Return: protection attributes of the page-table entry in the enum
+ * kvm_pgtable_prot format.
+ */
+enum kvm_pgtable_prot kvm_pgtable_stage2_pte_prot(kvm_pte_t pte);
+
+/**
+ * kvm_pgtable_hyp_pte_prot() - Retrieve the protection attributes of a stage-1
+ * Page-Table Entry.
+ * @pte: Page-table entry
+ *
+ * Return: protection attributes of the page-table entry in the enum
+ * kvm_pgtable_prot format.
+ */
+enum kvm_pgtable_prot kvm_pgtable_hyp_pte_prot(kvm_pte_t pte);
#endif /* __ARM64_KVM_PGTABLE_H__ */
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 1915489bb127..a6eda8f23cb6 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -363,6 +363,26 @@ static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
return 0;
}

+enum kvm_pgtable_prot kvm_pgtable_hyp_pte_prot(kvm_pte_t pte)
+{
+ enum kvm_pgtable_prot prot = pte & KVM_PTE_LEAF_ATTR_HI_SW;
+ u32 ap;
+
+ if (!kvm_pte_valid(pte))
+ return prot;
+
+ if (!(pte & KVM_PTE_LEAF_ATTR_HI_S1_XN))
+ prot |= KVM_PGTABLE_PROT_X;
+
+ ap = FIELD_GET(KVM_PTE_LEAF_ATTR_LO_S1_AP, pte);
+ if (ap == KVM_PTE_LEAF_ATTR_LO_S1_AP_RO)
+ prot |= KVM_PGTABLE_PROT_R;
+ else if (ap == KVM_PTE_LEAF_ATTR_LO_S1_AP_RW)
+ prot |= KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W;
+
+ return prot;
+}
+
static bool hyp_pte_needs_update(kvm_pte_t old, kvm_pte_t new)
{
/*
@@ -565,6 +585,23 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p
return 0;
}

+enum kvm_pgtable_prot kvm_pgtable_stage2_pte_prot(kvm_pte_t pte)
+{
+ enum kvm_pgtable_prot prot = pte & KVM_PTE_LEAF_ATTR_HI_SW;
+
+ if (!kvm_pte_valid(pte))
+ return prot;
+
+ if (pte & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R)
+ prot |= KVM_PGTABLE_PROT_R;
+ if (pte & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W)
+ prot |= KVM_PGTABLE_PROT_W;
+ if (!(pte & KVM_PTE_LEAF_ATTR_HI_S2_XN))
+ prot |= KVM_PGTABLE_PROT_X;
+
+ return prot;
+}
+
static bool stage2_pte_needs_update(kvm_pte_t old, kvm_pte_t new)
{
if (!kvm_pte_valid(old) || !kvm_pte_valid(new))
--
2.32.0.432.gabb21c7263-goog