KVM: arm64: Convert translation level parameter to s8

With the introduction of FEAT_LPA2, the Arm ARM adds a new level of
translation, level -1, so levels can now be in the range [-1;3]. 3 is
always the last level and the first level is determined based on the
number of VA bits in use.

Convert level variables to use a signed type in preparation for
supporting this new level -1.

Since the last level is always anchored at 3, and the first level varies
to suit the number of VA/IPA bits, take the opportunity to replace
KVM_PGTABLE_MAX_LEVELS with the 2 macros KVM_PGTABLE_FIRST_LEVEL and
KVM_PGTABLE_LAST_LEVEL. This removes the assumption from the code that
levels run from 0 to KVM_PGTABLE_MAX_LEVELS - 1, which will soon no
longer be true.

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231127111737.1897081-9-ryan.roberts@arm.com

Author: ryanhrob

arch/arm64/include/asm/kvm_emulate.h

@@ -409,7 +409,7 @@ static __always_inline u8 kvm_vcpu_trap_get_fault_type(const struct kvm_vcpu *vc
 	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_TYPE;
 }
 
-static __always_inline u8 kvm_vcpu_trap_get_fault_level(const struct kvm_vcpu *vcpu)
+static __always_inline s8 kvm_vcpu_trap_get_fault_level(const struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_LEVEL;
 }

arch/arm64/include/asm/kvm_pgtable.h

@@ -11,7 +11,8 @@
 #include <linux/kvm_host.h>
 #include <linux/types.h>
 
-#define KVM_PGTABLE_MAX_LEVELS		4U
+#define KVM_PGTABLE_FIRST_LEVEL		0
+#define KVM_PGTABLE_LAST_LEVEL		3
 
 /*
  * The largest supported block sizes for KVM (no 52-bit PA support):
@@ -20,9 +21,9 @@
  *  - 64K (level 2):	512MB
  */
 #ifdef CONFIG_ARM64_4K_PAGES
-#define KVM_PGTABLE_MIN_BLOCK_LEVEL	1U
+#define KVM_PGTABLE_MIN_BLOCK_LEVEL	1
 #else
-#define KVM_PGTABLE_MIN_BLOCK_LEVEL	2U
+#define KVM_PGTABLE_MIN_BLOCK_LEVEL	2
 #endif
 
 #define kvm_lpa2_is_enabled()		system_supports_lpa2()
@@ -103,28 +104,28 @@ static inline kvm_pfn_t kvm_pte_to_pfn(kvm_pte_t pte)
 	return __phys_to_pfn(kvm_pte_to_phys(pte));
 }
 
-static inline u64 kvm_granule_shift(u32 level)
+static inline u64 kvm_granule_shift(s8 level)
 {
-	/* Assumes KVM_PGTABLE_MAX_LEVELS is 4 */
+	/* Assumes KVM_PGTABLE_LAST_LEVEL is 3 */
 	return ARM64_HW_PGTABLE_LEVEL_SHIFT(level);
 }
 
-static inline u64 kvm_granule_size(u32 level)
+static inline u64 kvm_granule_size(s8 level)
 {
 	return BIT(kvm_granule_shift(level));
 }
 
-static inline bool kvm_level_supports_block_mapping(u32 level)
+static inline bool kvm_level_supports_block_mapping(s8 level)
 {
 	return level >= KVM_PGTABLE_MIN_BLOCK_LEVEL;
 }
 
 static inline u32 kvm_supported_block_sizes(void)
 {
-	u32 level = KVM_PGTABLE_MIN_BLOCK_LEVEL;
+	s8 level = KVM_PGTABLE_MIN_BLOCK_LEVEL;
 	u32 r = 0;
 
-	for (; level < KVM_PGTABLE_MAX_LEVELS; level++)
+	for (; level <= KVM_PGTABLE_LAST_LEVEL; level++)
 		r |= BIT(kvm_granule_shift(level));
 
 	return r;
@@ -169,7 +170,7 @@ struct kvm_pgtable_mm_ops {
 	void*		(*zalloc_page)(void *arg);
 	void*		(*zalloc_pages_exact)(size_t size);
 	void		(*free_pages_exact)(void *addr, size_t size);
-	void		(*free_unlinked_table)(void *addr, u32 level);
+	void		(*free_unlinked_table)(void *addr, s8 level);
 	void		(*get_page)(void *addr);
 	void		(*put_page)(void *addr);
 	int		(*page_count)(void *addr);
@@ -265,7 +266,7 @@ struct kvm_pgtable_visit_ctx {
 	u64					start;
 	u64					addr;
 	u64					end;
-	u32					level;
+	s8					level;
 	enum kvm_pgtable_walk_flags		flags;
 };
 
@@ -368,7 +369,7 @@ static inline bool kvm_pgtable_walk_lock_held(void)
  */
 struct kvm_pgtable {
 	u32					ia_bits;
-	u32					start_level;
+	s8					start_level;
 	kvm_pteref_t				pgd;
 	struct kvm_pgtable_mm_ops		*mm_ops;
 
@@ -502,7 +503,7 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
  * The page-table is assumed to be unreachable by any hardware walkers prior to
  * freeing and therefore no TLB invalidation is performed.
  */
-void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level);
+void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, s8 level);
 
 /**
  * kvm_pgtable_stage2_create_unlinked() - Create an unlinked stage-2 paging structure.
@@ -526,7 +527,7 @@ void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *p
  * an ERR_PTR(error) on failure.
  */
 kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt,
-					      u64 phys, u32 level,
+					      u64 phys, s8 level,
 					      enum kvm_pgtable_prot prot,
 					      void *mc, bool force_pte);
 
@@ -752,7 +753,7 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
  * Return: 0 on success, negative error code on failure.
  */
 int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
-			 kvm_pte_t *ptep, u32 *level);
+			 kvm_pte_t *ptep, s8 *level);
 
 /**
  * kvm_pgtable_stage2_pte_prot() - Retrieve the protection attributes of a

arch/arm64/include/asm/kvm_pkvm.h

@@ -56,10 +56,11 @@ static inline unsigned long hyp_vm_table_pages(void)
 
 static inline unsigned long __hyp_pgtable_max_pages(unsigned long nr_pages)
 {
-	unsigned long total = 0, i;
+	unsigned long total = 0;
+	int i;
 
 	/* Provision the worst case scenario */
-	for (i = 0; i < KVM_PGTABLE_MAX_LEVELS; i++) {
+	for (i = KVM_PGTABLE_FIRST_LEVEL; i <= KVM_PGTABLE_LAST_LEVEL; i++) {
 		nr_pages = DIV_ROUND_UP(nr_pages, PTRS_PER_PTE);
 		total += nr_pages;
 	}

arch/arm64/kvm/hyp/nvhe/mem_protect.c

@@ -91,7 +91,7 @@ static void host_s2_put_page(void *addr)
 	hyp_put_page(&host_s2_pool, addr);
 }
 
-static void host_s2_free_unlinked_table(void *addr, u32 level)
+static void host_s2_free_unlinked_table(void *addr, s8 level)
 {
 	kvm_pgtable_stage2_free_unlinked(&host_mmu.mm_ops, addr, level);
 }
@@ -443,7 +443,7 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range)
 {
 	struct kvm_mem_range cur;
 	kvm_pte_t pte;
-	u32 level;
+	s8 level;
 	int ret;
 
 	hyp_assert_lock_held(&host_mmu.lock);
@@ -462,7 +462,7 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range)
 		cur.start = ALIGN_DOWN(addr, granule);
 		cur.end = cur.start + granule;
 		level++;
-	} while ((level < KVM_PGTABLE_MAX_LEVELS) &&
+	} while ((level <= KVM_PGTABLE_LAST_LEVEL) &&
 			!(kvm_level_supports_block_mapping(level) &&
 			  range_included(&cur, range)));
 

arch/arm64/kvm/hyp/nvhe/mm.c

@@ -260,7 +260,7 @@ static void fixmap_clear_slot(struct hyp_fixmap_slot *slot)
 	 * https://lore.kernel.org/kvm/20221017115209.2099-1-will@kernel.org/T/#mf10dfbaf1eaef9274c581b81c53758918c1d0f03
 	 */
 	dsb(ishst);
-	__tlbi_level(vale2is, __TLBI_VADDR(addr, 0), (KVM_PGTABLE_MAX_LEVELS - 1));
+	__tlbi_level(vale2is, __TLBI_VADDR(addr, 0), KVM_PGTABLE_LAST_LEVEL);
 	dsb(ish);
 	isb();
 }
@@ -275,7 +275,7 @@ static int __create_fixmap_slot_cb(const struct kvm_pgtable_visit_ctx *ctx,
 {
 	struct hyp_fixmap_slot *slot = per_cpu_ptr(&fixmap_slots, (u64)ctx->arg);
 
-	if (!kvm_pte_valid(ctx->old) || ctx->level != KVM_PGTABLE_MAX_LEVELS - 1)
+	if (!kvm_pte_valid(ctx->old) || ctx->level != KVM_PGTABLE_LAST_LEVEL)
 		return -EINVAL;
 
 	slot->addr = ctx->addr;

arch/arm64/kvm/hyp/nvhe/setup.c

@@ -181,7 +181,7 @@ static int fix_host_ownership_walker(const struct kvm_pgtable_visit_ctx *ctx,
 	if (!kvm_pte_valid(ctx->old))
 		return 0;
 
-	if (ctx->level != (KVM_PGTABLE_MAX_LEVELS - 1))
+	if (ctx->level != KVM_PGTABLE_LAST_LEVEL)
 		return -EINVAL;
 
 	phys = kvm_pte_to_phys(ctx->old);