KVM: arm64: Add support for relaxing stage-2 perms in generic page-table code

Add support for relaxing the permissions of a stage-2 mapping (i.e.
adding additional permissions) to the generic page-table code.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20200911132529.19844-17-will@kernel.org

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 77c027456c61408204dbecbdaae0c5dccf4d676a..52ab38db04c7ed0c95c460a65606fadbd4a68719 100644 (file)
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -236,6 +236,25 @@ kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr);
  */
 kvm_pte_t kvm_pgtable_stage2_mkold(struct kvm_pgtable *pgt, u64 addr);
 
+/**
+ * kvm_pgtable_stage2_relax_perms() - Relax the permissions enforced by a
+ *                                   page-table entry.
+ * @pgt:       Page-table structure initialised by kvm_pgtable_stage2_init().
+ * @addr:      Intermediate physical address to identify the page-table entry.
+ * @prot:      Additional permissions to grant for the mapping.
+ *
+ * The offset of @addr within a page is ignored.
+ *
+ * If there is a valid, leaf page-table entry used to translate @addr, then
+ * relax the permissions in that entry according to the read, write and
+ * execute permissions specified by @prot. No permissions are removed, and
+ * TLB invalidation is performed after updating the entry.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
+                                  enum kvm_pgtable_prot prot);
+
 /**
  * kvm_pgtable_stage2_is_young() - Test whether a page-table entry has the
  *                                access flag set.

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index d382756a527c367e99c26d4015408ed50dc5a20b..603d6b415337dbc056a6b5c8541d59386f28e338 100644 (file)
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -782,6 +782,26 @@ bool kvm_pgtable_stage2_is_young(struct kvm_pgtable *pgt, u64 addr)
        return pte & KVM_PTE_LEAF_ATTR_LO_S2_AF;
 }
 
+int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
+                                  enum kvm_pgtable_prot prot)
+{
+       int ret;
+       kvm_pte_t set = 0, clr = 0;
+
+       if (prot & KVM_PGTABLE_PROT_R)
+               set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R;
+
+       if (prot & KVM_PGTABLE_PROT_W)
+               set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;
+
+       if (prot & KVM_PGTABLE_PROT_X)
+               clr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;
+
+       ret = stage2_update_leaf_attrs(pgt, addr, 1, set, clr, NULL);
+       kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, pgt->mmu, addr, 0);
+       return ret;
+}
+
 static int stage2_flush_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
                               enum kvm_pgtable_walk_flags flag,
                               void * const arg)