[RFC PATCH v2 2/8] KVM: arm64: Add KVM_PGTABLE_WALK_HW_DBM for HW DBM support

[Shameer Kolothum]

KVM_PGTABLE_WALK_HW_DBM - Indicates page table walk is for HW DBM
 related updates.

No functional changes here. Only apply any HW DBM bit updates to last
level only. These will be used by a future commit where we will add
support for HW DBM.

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
---
 arch/arm64/include/asm/kvm_pgtable.h |  3 +++
 arch/arm64/kvm/hyp/pgtable.c         | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index d3e354bb8351..3f96bdd2086f 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -219,6 +219,8 @@ typedef bool (*kvm_pgtable_force_pte_cb_t)(u64 addr, u64 end,
  * @KVM_PGTABLE_WALK_SKIP_CMO:		Visit and update table entries
  *					without Cache maintenance
  *					operations required.
+ * @KVM_PGTABLE_WALK_HW_DBM:		Indicates that the attribute update is
+ *					HW DBM related.
  */
 enum kvm_pgtable_walk_flags {
 	KVM_PGTABLE_WALK_LEAF			= BIT(0),
@@ -228,6 +230,7 @@ enum kvm_pgtable_walk_flags {
 	KVM_PGTABLE_WALK_HANDLE_FAULT		= BIT(4),
 	KVM_PGTABLE_WALK_SKIP_BBM_TLBI		= BIT(5),
 	KVM_PGTABLE_WALK_SKIP_CMO		= BIT(6),
+	KVM_PGTABLE_WALK_HW_DBM			= BIT(7),
 };
 
 struct kvm_pgtable_visit_ctx {
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index f155b8c9e98c..1e65b8c97059 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -67,6 +67,11 @@ struct kvm_pgtable_walk_data {
 	const u64			end;
 };
 
+static bool kvm_pgtable_walk_hw_dbm(const struct kvm_pgtable_visit_ctx *ctx)
+{
+	return ctx->flags & KVM_PGTABLE_WALK_HW_DBM;
+}
+
 static bool kvm_pgtable_walk_skip_bbm_tlbi(const struct kvm_pgtable_visit_ctx *ctx)
 {
 	return unlikely(ctx->flags & KVM_PGTABLE_WALK_SKIP_BBM_TLBI);
@@ -1164,6 +1169,11 @@ static int stage2_attr_walker(const struct kvm_pgtable_visit_ctx *ctx,
 	if (!kvm_pte_valid(ctx->old))
 		return -EAGAIN;
 
+	/* Only apply HW DBM for last level */
+	if (kvm_pgtable_walk_hw_dbm(ctx) &&
+	    ctx->level != (KVM_PGTABLE_MAX_LEVELS - 1))
+		return 0;
+
 	data->level = ctx->level;
 	data->pte = pte;
 	pte &= ~data->attr_clr;
-- 
2.34.1