Re: [PATCH v5 03/14] KVM: arm64: Pass mm_ops through the visitor context

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Hi Oliver,

On 11/8/22 5:56 AM, Oliver Upton wrote:

As a prerequisite for getting visitors off of struct kvm_pgtable, pass
mm_ops through the visitor context.

No functional change intended.

Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
---
  arch/arm64/include/asm/kvm_pgtable.h |  1 +
  arch/arm64/kvm/hyp/nvhe/setup.c      |  3 +-
  arch/arm64/kvm/hyp/pgtable.c         | 63 +++++++++++-----------------
  3 files changed, 26 insertions(+), 41 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 14d4b68a1e92..a752793482cb 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -203,6 +203,7 @@ struct kvm_pgtable_visit_ctx {
  	kvm_pte_t				*ptep;
  	kvm_pte_t				old;
  	void					*arg;
+	struct kvm_pgtable_mm_ops		*mm_ops;
  	u64					addr;
  	u64					end;
  	u32					level;
diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index 6af443c9d78e..1068338d77f3 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -189,7 +189,7 @@ static void hpool_put_page(void *addr)
  static int finalize_host_mappings_walker(const struct kvm_pgtable_visit_ctx *ctx,
  					 enum kvm_pgtable_walk_flags visit)
  {
-	struct kvm_pgtable_mm_ops *mm_ops = ctx->arg;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
  	enum kvm_pgtable_prot prot;
  	enum pkvm_page_state state;
  	phys_addr_t phys;
@@ -239,7 +239,6 @@ static int finalize_host_mappings(void)
  	struct kvm_pgtable_walker walker = {
  		.cb	= finalize_host_mappings_walker,
  		.flags	= KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
-		.arg	= pkvm_pgtable.mm_ops,
  	};
  	int i, ret;
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c 
index fb3696b3a997..db25e81a9890 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -181,9 +181,10 @@ static int kvm_pgtable_visitor_cb(struct kvm_pgtable_walk_data *data,
  }
static int __kvm_pgtable_walk(struct kvm_pgtable_walk_data *data, 
-			      kvm_pte_t *pgtable, u32 level);
+			      struct kvm_pgtable_mm_ops *mm_ops, kvm_pte_t *pgtable, u32 level);
static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data, 
+				      struct kvm_pgtable_mm_ops *mm_ops,
  				      kvm_pte_t *ptep, u32 level)
  {
  	enum kvm_pgtable_walk_flags flags = data->walker->flags;
@@ -191,6 +192,7 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
  		.ptep	= ptep,
  		.old	= READ_ONCE(*ptep),
  		.arg	= data->walker->arg,
+		.mm_ops	= mm_ops,
  		.addr	= data->addr,
  		.end	= data->end,
  		.level	= level,


I don't understand why we need @mm_ops argument for this function:

  - @mm_ops is always fetched from the associated page table struct.
    (data->pgt->mm_ops) in upper layer (_kvm_pgtable_walk()). However,
    the argument starts to be used in lower layer (__kvm_pgtable_visit()),
    meaning the argument isn't needed by the upper layers.

  - @mm_ops isn't need by __kvm_pgtable_walk(). So the argument isn't needed by the
    function.



@@ -218,8 +220,8 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
  		goto out;
  	}
- childp = kvm_pte_follow(ctx.old, data->pgt->mm_ops); 
-	ret = __kvm_pgtable_walk(data, childp, level + 1);
+	childp = kvm_pte_follow(ctx.old, mm_ops);
+	ret = __kvm_pgtable_walk(data, mm_ops, childp, level + 1);
  	if (ret)
  		goto out;
@@ -231,7 +233,7 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data, 
  }
static int __kvm_pgtable_walk(struct kvm_pgtable_walk_data *data, 
-			      kvm_pte_t *pgtable, u32 level)
+			      struct kvm_pgtable_mm_ops *mm_ops, kvm_pte_t *pgtable, u32 level)
  {
  	u32 idx;
  	int ret = 0;
@@ -245,7 +247,7 @@ static int __kvm_pgtable_walk(struct kvm_pgtable_walk_data *data,
  		if (data->addr >= data->end)
  			break;
- ret = __kvm_pgtable_visit(data, ptep, level); 
+		ret = __kvm_pgtable_visit(data, mm_ops, ptep, level);
  		if (ret)
  			break;
  	}
@@ -269,7 +271,7 @@ static int _kvm_pgtable_walk(struct kvm_pgtable_walk_data *data)
  	for (idx = kvm_pgd_page_idx(data); data->addr < data->end; ++idx) {
  		kvm_pte_t *ptep = &pgt->pgd[idx * PTRS_PER_PTE];
- ret = __kvm_pgtable_walk(data, ptep, pgt->start_level); 
+		ret = __kvm_pgtable_walk(data, pgt->mm_ops, ptep, pgt->start_level);
  		if (ret)
  			break;
  	}


As I mentioned above, @mm_ops isn't needed by __kvm_pgtable_walk() and __kvm_pgtable_visit()
can fetch it directly from data->pgtable->mm_ops.


@@ -332,7 +334,6 @@ int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
  struct hyp_map_data {
  	u64				phys;
  	kvm_pte_t			attr;
-	struct kvm_pgtable_mm_ops	*mm_ops;
  };
static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep) 
@@ -400,7 +401,7 @@ static bool hyp_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
  	if (ctx->old == new)
  		return true;
  	if (!kvm_pte_valid(ctx->old))
-		data->mm_ops->get_page(ctx->ptep);
+		ctx->mm_ops->get_page(ctx->ptep);
  	else if (WARN_ON((ctx->old ^ new) & ~KVM_PTE_LEAF_ATTR_HI_SW))
  		return false;
@@ -413,7 +414,7 @@ static int hyp_map_walker(const struct kvm_pgtable_visit_ctx *ctx, 
  {
  	kvm_pte_t *childp;
  	struct hyp_map_data *data = ctx->arg;
-	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
if (hyp_map_walker_try_leaf(ctx, data)) 
  		return 0;
@@ -436,7 +437,6 @@ int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
  	int ret;
  	struct hyp_map_data map_data = {
  		.phys	= ALIGN_DOWN(phys, PAGE_SIZE),
-		.mm_ops	= pgt->mm_ops,
  	};
  	struct kvm_pgtable_walker walker = {
  		.cb	= hyp_map_walker,
@@ -454,18 +454,13 @@ int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
  	return ret;
  }
-struct hyp_unmap_data { 
-	u64				unmapped;
-	struct kvm_pgtable_mm_ops	*mm_ops;
-};
-
  static int hyp_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
  			    enum kvm_pgtable_walk_flags visit)
  {
  	kvm_pte_t *childp = NULL;
  	u64 granule = kvm_granule_size(ctx->level);
-	struct hyp_unmap_data *data = ctx->arg;
-	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+	u64 *unmapped = ctx->arg;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
if (!kvm_pte_valid(ctx->old)) 
  		return -EINVAL;
@@ -486,7 +481,7 @@ static int hyp_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
  		kvm_clear_pte(ctx->ptep);
  		dsb(ishst);
  		__tlbi_level(vale2is, __TLBI_VADDR(ctx->addr, 0), ctx->level);
-		data->unmapped += granule;
+		*unmapped += granule;
  	}
dsb(ish); 
@@ -501,12 +496,10 @@ static int hyp_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
u64 kvm_pgtable_hyp_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size) 
  {
-	struct hyp_unmap_data unmap_data = {
-		.mm_ops	= pgt->mm_ops,
-	};
+	u64 unmapped = 0;
  	struct kvm_pgtable_walker walker = {
  		.cb	= hyp_unmap_walker,
-		.arg	= &unmap_data,
+		.arg	= &unmapped,
  		.flags	= KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
  	};
@@ -514,7 +507,7 @@ u64 kvm_pgtable_hyp_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size) 
  		return 0;
kvm_pgtable_walk(pgt, addr, size, &walker); 
-	return unmap_data.unmapped;
+	return unmapped;
  }
int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits, 
@@ -538,7 +531,7 @@ int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits,
  static int hyp_free_walker(const struct kvm_pgtable_visit_ctx *ctx,
  			   enum kvm_pgtable_walk_flags visit)
  {
-	struct kvm_pgtable_mm_ops *mm_ops = ctx->arg;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
if (!kvm_pte_valid(ctx->old)) 
  		return 0;
@@ -556,7 +549,6 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
  	struct kvm_pgtable_walker walker = {
  		.cb	= hyp_free_walker,
  		.flags	= KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
-		.arg	= pgt->mm_ops,
  	};
WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker)); 
@@ -575,8 +567,6 @@ struct stage2_map_data {
  	struct kvm_s2_mmu		*mmu;
  	void				*memcache;
- struct kvm_pgtable_mm_ops *mm_ops; 
-
  	/* Force mappings to page granularity */
  	bool				force_pte;
  };
@@ -725,7 +715,7 @@ static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
  	kvm_pte_t new;
  	u64 granule = kvm_granule_size(ctx->level), phys = data->phys;
  	struct kvm_pgtable *pgt = data->mmu->pgt;
-	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
if (!stage2_leaf_mapping_allowed(ctx, data)) 
  		return -E2BIG;
@@ -773,7 +763,7 @@ static int stage2_map_walk_table_pre(const struct kvm_pgtable_visit_ctx *ctx,
  	if (!stage2_leaf_mapping_allowed(ctx, data))
  		return 0;
- data->childp = kvm_pte_follow(ctx->old, data->mm_ops); 
+	data->childp = kvm_pte_follow(ctx->old, ctx->mm_ops);
  	kvm_clear_pte(ctx->ptep);
/* 
@@ -789,7 +779,7 @@ static int stage2_map_walk_table_pre(const struct kvm_pgtable_visit_ctx *ctx,
  static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx,
  				struct stage2_map_data *data)
  {
-	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
  	kvm_pte_t *childp;
  	int ret;
@@ -831,7 +821,7 @@ static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx, 
  static int stage2_map_walk_table_post(const struct kvm_pgtable_visit_ctx *ctx,
  				      struct stage2_map_data *data)
  {
-	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
  	kvm_pte_t *childp;
  	int ret = 0;
@@ -898,7 +888,6 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, 
  		.phys		= ALIGN_DOWN(phys, PAGE_SIZE),
  		.mmu		= pgt->mmu,
  		.memcache	= mc,
-		.mm_ops		= pgt->mm_ops,
  		.force_pte	= pgt->force_pte_cb && pgt->force_pte_cb(addr, addr + size, prot),
  	};
  	struct kvm_pgtable_walker walker = {
@@ -929,7 +918,6 @@ int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size,
  		.phys		= KVM_PHYS_INVALID,
  		.mmu		= pgt->mmu,
  		.memcache	= mc,
-		.mm_ops		= pgt->mm_ops,
  		.owner_id	= owner_id,
  		.force_pte	= true,
  	};
@@ -953,7 +941,7 @@ static int stage2_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
  {
  	struct kvm_pgtable *pgt = ctx->arg;
  	struct kvm_s2_mmu *mmu = pgt->mmu;
-	struct kvm_pgtable_mm_ops *mm_ops = pgt->mm_ops;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
  	kvm_pte_t *childp = NULL;
  	bool need_flush = false;
@@ -1007,7 +995,6 @@ struct stage2_attr_data { 
  	kvm_pte_t			attr_clr;
  	kvm_pte_t			pte;
  	u32				level;
-	struct kvm_pgtable_mm_ops	*mm_ops;
  };
static int stage2_attr_walker(const struct kvm_pgtable_visit_ctx *ctx, 
@@ -1015,7 +1002,7 @@ static int stage2_attr_walker(const struct kvm_pgtable_visit_ctx *ctx,
  {
  	kvm_pte_t pte = ctx->old;
  	struct stage2_attr_data *data = ctx->arg;
-	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
if (!kvm_pte_valid(ctx->old)) 
  		return 0;
@@ -1055,7 +1042,6 @@ static int stage2_update_leaf_attrs(struct kvm_pgtable *pgt, u64 addr,
  	struct stage2_attr_data data = {
  		.attr_set	= attr_set & attr_mask,
  		.attr_clr	= attr_clr & attr_mask,
-		.mm_ops		= pgt->mm_ops,
  	};
  	struct kvm_pgtable_walker walker = {
  		.cb		= stage2_attr_walker,
@@ -1198,7 +1184,7 @@ int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu,
  static int stage2_free_walker(const struct kvm_pgtable_visit_ctx *ctx,
  			      enum kvm_pgtable_walk_flags visit)
  {
-	struct kvm_pgtable_mm_ops *mm_ops = ctx->arg;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
if (!stage2_pte_is_counted(ctx->old)) 
  		return 0;
@@ -1218,7 +1204,6 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
  		.cb	= stage2_free_walker,
  		.flags	= KVM_PGTABLE_WALK_LEAF |
  			  KVM_PGTABLE_WALK_TABLE_POST,
-		.arg	= pgt->mm_ops,
  	};
WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker)); 



Thanks,
Gavin

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