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From:   Hamza Mahfooz <someguy@effective-light.com>
To:     linux-kernel@vger.kernel.org
Cc:     Peter Xu <peterx@redhat.com>,
        Hamza Mahfooz <someguy@effective-light.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        kvm@vger.kernel.org
Subject: [PATCH v3] KVM: const-ify all relevant uses of struct kvm_memory_slot
Date:   Mon,  2 Aug 2021 15:43:01 -0400
Message-Id: <20210802194302.60796-1-someguy@effective-light.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

As alluded to in commit f36f3f2846b5 ("KVM: add "new" argument to
kvm_arch_commit_memory_region"), a bunch of other places where struct
kvm_memory_slot is used, needs to be refactored to preserve the
"const"ness of struct kvm_memory_slot across-the-board.

Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
---
v2: fix an issue regarding an incorrect start_level being passed to
    rmap_walk_init_level()

v3: apparently the memcpy() is redundant, so revert the body of
    slot_rmap_walk_init() back to it's previous state.
---
 arch/x86/include/asm/kvm_host.h |  4 ++--
 arch/x86/kvm/mmu/mmu.c          | 42 ++++++++++++++++-----------------
 arch/x86/kvm/mmu/mmu_internal.h |  4 ++--
 arch/x86/kvm/mmu/tdp_mmu.c      |  7 +++---
 arch/x86/kvm/mmu/tdp_mmu.h      |  6 ++---
 arch/x86/kvm/x86.c              |  7 ++----
 6 files changed, 34 insertions(+), 36 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 974cbfb1eefe..a195e1c32018 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1536,12 +1536,12 @@ void kvm_mmu_uninit_vm(struct kvm *kvm);
 void kvm_mmu_after_set_cpuid(struct kvm_vcpu *vcpu);
 void kvm_mmu_reset_context(struct kvm_vcpu *vcpu);
 void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
-				      struct kvm_memory_slot *memslot,
+				      const struct kvm_memory_slot *memslot,
 				      int start_level);
 void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
 				   const struct kvm_memory_slot *memslot);
 void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
-				   struct kvm_memory_slot *memslot);
+				   const struct kvm_memory_slot *memslot);
 void kvm_mmu_zap_all(struct kvm *kvm);
 void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen);
 unsigned long kvm_mmu_calculate_default_mmu_pages(struct kvm *kvm);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 66f7f5bc3482..833b493d87bf 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -786,7 +786,7 @@ static struct kvm_lpage_info *lpage_info_slot(gfn_t gfn,
 	return &slot->arch.lpage_info[level - 2][idx];
 }
 
-static void update_gfn_disallow_lpage_count(struct kvm_memory_slot *slot,
+static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot,
 					    gfn_t gfn, int count)
 {
 	struct kvm_lpage_info *linfo;
@@ -799,12 +799,12 @@ static void update_gfn_disallow_lpage_count(struct kvm_memory_slot *slot,
 	}
 }
 
-void kvm_mmu_gfn_disallow_lpage(struct kvm_memory_slot *slot, gfn_t gfn)
+void kvm_mmu_gfn_disallow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn)
 {
 	update_gfn_disallow_lpage_count(slot, gfn, 1);
 }
 
-void kvm_mmu_gfn_allow_lpage(struct kvm_memory_slot *slot, gfn_t gfn)
+void kvm_mmu_gfn_allow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn)
 {
 	update_gfn_disallow_lpage_count(slot, gfn, -1);
 }
@@ -991,7 +991,7 @@ static void pte_list_remove(struct kvm_rmap_head *rmap_head, u64 *sptep)
 }
 
 static struct kvm_rmap_head *__gfn_to_rmap(gfn_t gfn, int level,
-					   struct kvm_memory_slot *slot)
+					   const struct kvm_memory_slot *slot)
 {
 	unsigned long idx;
 
@@ -1218,7 +1218,7 @@ static bool spte_wrprot_for_clear_dirty(u64 *sptep)
  * Returns true iff any D or W bits were cleared.
  */
 static bool __rmap_clear_dirty(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
-			       struct kvm_memory_slot *slot)
+			       const struct kvm_memory_slot *slot)
 {
 	u64 *sptep;
 	struct rmap_iterator iter;
@@ -1377,7 +1377,7 @@ static bool rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn)
 }
 
 static bool kvm_zap_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
-			  struct kvm_memory_slot *slot)
+			  const struct kvm_memory_slot *slot)
 {
 	u64 *sptep;
 	struct rmap_iterator iter;
@@ -1442,7 +1442,7 @@ static bool kvm_set_pte_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
 
 struct slot_rmap_walk_iterator {
 	/* input fields. */
-	struct kvm_memory_slot *slot;
+	const struct kvm_memory_slot *slot;
 	gfn_t start_gfn;
 	gfn_t end_gfn;
 	int start_level;
@@ -1469,7 +1469,7 @@ rmap_walk_init_level(struct slot_rmap_walk_iterator *iterator, int level)
 
 static void
 slot_rmap_walk_init(struct slot_rmap_walk_iterator *iterator,
-		    struct kvm_memory_slot *slot, int start_level,
+		    const struct kvm_memory_slot *slot, int start_level,
 		    int end_level, gfn_t start_gfn, gfn_t end_gfn)
 {
 	iterator->slot = slot;
@@ -5276,12 +5276,13 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_max_root_level,
 EXPORT_SYMBOL_GPL(kvm_configure_mmu);
 
 /* The return value indicates if tlb flush on all vcpus is needed. */
-typedef bool (*slot_level_handler) (struct kvm *kvm, struct kvm_rmap_head *rmap_head,
-				    struct kvm_memory_slot *slot);
+typedef bool (*slot_level_handler) (struct kvm *kvm,
+				    struct kvm_rmap_head *rmap_head,
+				    const struct kvm_memory_slot *slot);
 
 /* The caller should hold mmu-lock before calling this function. */
 static __always_inline bool
-slot_handle_level_range(struct kvm *kvm, struct kvm_memory_slot *memslot,
+slot_handle_level_range(struct kvm *kvm, const struct kvm_memory_slot *memslot,
 			slot_level_handler fn, int start_level, int end_level,
 			gfn_t start_gfn, gfn_t end_gfn, bool flush_on_yield,
 			bool flush)
@@ -5308,7 +5309,7 @@ slot_handle_level_range(struct kvm *kvm, struct kvm_memory_slot *memslot,
 }
 
 static __always_inline bool
-slot_handle_level(struct kvm *kvm, struct kvm_memory_slot *memslot,
+slot_handle_level(struct kvm *kvm, const struct kvm_memory_slot *memslot,
 		  slot_level_handler fn, int start_level, int end_level,
 		  bool flush_on_yield)
 {
@@ -5319,7 +5320,7 @@ slot_handle_level(struct kvm *kvm, struct kvm_memory_slot *memslot,
 }
 
 static __always_inline bool
-slot_handle_leaf(struct kvm *kvm, struct kvm_memory_slot *memslot,
+slot_handle_leaf(struct kvm *kvm, const struct kvm_memory_slot *memslot,
 		 slot_level_handler fn, bool flush_on_yield)
 {
 	return slot_handle_level(kvm, memslot, fn, PG_LEVEL_4K,
@@ -5578,7 +5579,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
 				if (start >= end)
 					continue;
 
-				flush = slot_handle_level_range(kvm, memslot,
+				flush = slot_handle_level_range(kvm,
+						(const struct kvm_memory_slot *) memslot,
 						kvm_zap_rmapp, PG_LEVEL_4K,
 						KVM_MAX_HUGEPAGE_LEVEL, start,
 						end - 1, true, flush);
@@ -5606,13 +5608,13 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
 
 static bool slot_rmap_write_protect(struct kvm *kvm,
 				    struct kvm_rmap_head *rmap_head,
-				    struct kvm_memory_slot *slot)
+				    const struct kvm_memory_slot *slot)
 {
 	return __rmap_write_protect(kvm, rmap_head, false);
 }
 
 void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
-				      struct kvm_memory_slot *memslot,
+				      const struct kvm_memory_slot *memslot,
 				      int start_level)
 {
 	bool flush = false;
@@ -5648,7 +5650,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
 
 static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
 					 struct kvm_rmap_head *rmap_head,
-					 struct kvm_memory_slot *slot)
+					 const struct kvm_memory_slot *slot)
 {
 	u64 *sptep;
 	struct rmap_iterator iter;
@@ -5687,10 +5689,8 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
 }
 
 void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
-				   const struct kvm_memory_slot *memslot)
+				   const struct kvm_memory_slot *slot)
 {
-	/* FIXME: const-ify all uses of struct kvm_memory_slot.  */
-	struct kvm_memory_slot *slot = (struct kvm_memory_slot *)memslot;
 	bool flush = false;
 
 	if (kvm_memslots_have_rmaps(kvm)) {
@@ -5726,7 +5726,7 @@ void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
 }
 
 void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
-				   struct kvm_memory_slot *memslot)
+				   const struct kvm_memory_slot *memslot)
 {
 	bool flush = false;
 
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 35567293c1fd..ee4ad9c99219 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -124,8 +124,8 @@ static inline bool is_nx_huge_page_enabled(void)
 
 int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync);
 
-void kvm_mmu_gfn_disallow_lpage(struct kvm_memory_slot *slot, gfn_t gfn);
-void kvm_mmu_gfn_allow_lpage(struct kvm_memory_slot *slot, gfn_t gfn);
+void kvm_mmu_gfn_disallow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn);
+void kvm_mmu_gfn_allow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn);
 bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
 				    struct kvm_memory_slot *slot, u64 gfn,
 				    int min_level);
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 0853370bd811..5d8d69d56a81 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1242,8 +1242,8 @@ static bool wrprot_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
  * only affect leaf SPTEs down to min_level.
  * Returns true if an SPTE has been changed and the TLBs need to be flushed.
  */
-bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			     int min_level)
+bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm,
+			     const struct kvm_memory_slot *slot, int min_level)
 {
 	struct kvm_mmu_page *root;
 	bool spte_set = false;
@@ -1313,7 +1313,8 @@ static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
  * each SPTE. Returns true if an SPTE has been changed and the TLBs need to
  * be flushed.
  */
-bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
+bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm,
+				  const struct kvm_memory_slot *slot)
 {
 	struct kvm_mmu_page *root;
 	bool spte_set = false;
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index 1cae4485b3bc..49437dbb4804 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -61,10 +61,10 @@ bool kvm_tdp_mmu_age_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
 bool kvm_tdp_mmu_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
 bool kvm_tdp_mmu_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
 
-bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			     int min_level);
+bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm,
+			     const struct kvm_memory_slot *slot, int min_level);
 bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm,
-				  struct kvm_memory_slot *slot);
+				  const struct kvm_memory_slot *slot);
 void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm,
 				       struct kvm_memory_slot *slot,
 				       gfn_t gfn, unsigned long mask,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4116567f3d44..9f59f67e724b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11472,7 +11472,7 @@ static void kvm_mmu_update_cpu_dirty_logging(struct kvm *kvm, bool enable)
 
 static void kvm_mmu_slot_apply_flags(struct kvm *kvm,
 				     struct kvm_memory_slot *old,
-				     struct kvm_memory_slot *new,
+				     const struct kvm_memory_slot *new,
 				     enum kvm_mr_change change)
 {
 	bool log_dirty_pages = new->flags & KVM_MEM_LOG_DIRTY_PAGES;
@@ -11552,10 +11552,7 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
 		kvm_mmu_change_mmu_pages(kvm,
 				kvm_mmu_calculate_default_mmu_pages(kvm));
 
-	/*
-	 * FIXME: const-ify all uses of struct kvm_memory_slot.
-	 */
-	kvm_mmu_slot_apply_flags(kvm, old, (struct kvm_memory_slot *) new, change);
+	kvm_mmu_slot_apply_flags(kvm, old, new, change);
 
 	/* Free the arrays associated with the old memslot. */
 	if (change == KVM_MR_MOVE)
-- 
2.32.0