[PATCH 1/9] KVM: arm64: Add KVM_PGTABLE_WALK_REMOVED into ctx->flags

[Ricardo Koller <ricarkol@google.com>]

Add a flag to kvm_pgtable_visit_ctx, KVM_PGTABLE_WALK_REMOVED, to
indicate that the walk is on a removed table not accesible to the HW
page-table walker. Then use it to avoid doing break-before-make or
performing CMOs (Cache Maintenance Operations) when mapping a removed
table. This is safe as these removed tables are not visible to the HW
page-table walker. This will be used in a subsequent commit for
replacing huge-page block PTEs into tables of 4K PTEs.

Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
 arch/arm64/include/asm/kvm_pgtable.h |  8 ++++++++
 arch/arm64/kvm/hyp/pgtable.c         | 27 ++++++++++++++++-----------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 63f81b27a4e3..84a271647007 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -188,12 +188,15 @@ typedef bool (*kvm_pgtable_force_pte_cb_t)(u64 addr, u64 end,
  *					children.
  * @KVM_PGTABLE_WALK_SHARED:		Indicates the page-tables may be shared
  *					with other software walkers.
+ * @KVM_PGTABLE_WALK_REMOVED:		Indicates the page-tables are
+ *					removed: not visible to the HW walker.
  */
 enum kvm_pgtable_walk_flags {
 	KVM_PGTABLE_WALK_LEAF			= BIT(0),
 	KVM_PGTABLE_WALK_TABLE_PRE		= BIT(1),
 	KVM_PGTABLE_WALK_TABLE_POST		= BIT(2),
 	KVM_PGTABLE_WALK_SHARED			= BIT(3),
+	KVM_PGTABLE_WALK_REMOVED		= BIT(4),
 };
 
 struct kvm_pgtable_visit_ctx {
@@ -215,6 +218,11 @@ static inline bool kvm_pgtable_walk_shared(const struct kvm_pgtable_visit_ctx *c
 	return ctx->flags & KVM_PGTABLE_WALK_SHARED;
 }
 
+static inline bool kvm_pgtable_walk_removed(const struct kvm_pgtable_visit_ctx *ctx)
+{
+	return ctx->flags & KVM_PGTABLE_WALK_REMOVED;
+}
+
 /**
  * struct kvm_pgtable_walker - Hook into a page-table walk.
  * @cb:		Callback function to invoke during the walk.
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index b11cf2c618a6..87fd40d09056 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -717,14 +717,17 @@ static bool stage2_try_break_pte(const struct kvm_pgtable_visit_ctx *ctx,
 	if (!stage2_try_set_pte(ctx, KVM_INVALID_PTE_LOCKED))
 		return false;
 
-	/*
-	 * Perform the appropriate TLB invalidation based on the evicted pte
-	 * value (if any).
-	 */
-	if (kvm_pte_table(ctx->old, ctx->level))
-		kvm_call_hyp(__kvm_tlb_flush_vmid, mmu);
-	else if (kvm_pte_valid(ctx->old))
-		kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu, ctx->addr, ctx->level);
+	if (!kvm_pgtable_walk_removed(ctx)) {
+		/*
+		 * Perform the appropriate TLB invalidation based on the
+		 * evicted pte value (if any).
+		 */
+		if (kvm_pte_table(ctx->old, ctx->level))
+			kvm_call_hyp(__kvm_tlb_flush_vmid, mmu);
+		else if (kvm_pte_valid(ctx->old))
+			kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu,
+				     ctx->addr, ctx->level);
+	}
 
 	if (stage2_pte_is_counted(ctx->old))
 		mm_ops->put_page(ctx->ptep);
@@ -808,11 +811,13 @@ static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
 		return -EAGAIN;
 
 	/* Perform CMOs before installation of the guest stage-2 PTE */
-	if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
+	if (!kvm_pgtable_walk_removed(ctx) && mm_ops->dcache_clean_inval_poc &&
+	    stage2_pte_cacheable(pgt, new))
 		mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
-						granule);
+					       granule);
 
-	if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
+	if (!kvm_pgtable_walk_removed(ctx) && mm_ops->icache_inval_pou &&
+	    stage2_pte_executable(new))
 		mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
 
 	stage2_make_pte(ctx, new);
-- 
2.39.0.314.g84b9a713c41-goog