[PATCH 1/5] arm64: cpufeature: Add BBML3

[Linu Cherian <linu.cherian@arm.com>]

- As bbml2_noabort is functionally equivalent to bbml3,
  rename cpu/system_supports_bbml2_noabort to
  cpu/system_supports_bbml3.
  The ARM64 capability name is also renamed accordingly.

- As BBML2_NOABORT or the equivalent BBML3 is the
  kernel requirement for setting up linear map with
  block/contpte mappings and not BBML2, replace all
  bbml2 references with bbml3.

FEAT_BBML3, is introduced as part of 2025 Architecture Extensions.
https://developer.arm.com/documentation/109697/2026_03/2025-Architecture-Extensions

No functional changes are introduced with this patch.

Signed-off-by: Linu Cherian <linu.cherian@arm.com>
---
 arch/arm64/include/asm/cpufeature.h |  6 ++--
 arch/arm64/kernel/cpufeature.c      | 30 +++++------------
 arch/arm64/mm/contpte.c             | 21 +++++-------
 arch/arm64/mm/mmu.c                 | 52 ++++++++++++++---------------
 arch/arm64/mm/proc.S                |  4 +--
 arch/arm64/tools/cpucaps            |  2 +-
 6 files changed, 49 insertions(+), 66 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index a57870fa96db..d90040fb9de6 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -878,11 +878,11 @@ static inline bool system_supports_pmuv3(void)
 	return cpus_have_final_cap(ARM64_HAS_PMUV3);
 }
 
-bool cpu_supports_bbml2_noabort(void);
+bool cpu_supports_bbml3(void);
 
-static inline bool system_supports_bbml2_noabort(void)
+static inline bool system_supports_bbml3(void)
 {
-	return alternative_has_cap_unlikely(ARM64_HAS_BBML2_NOABORT);
+	return alternative_has_cap_unlikely(ARM64_HAS_BBML3);
 }
 
 int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9a22df0c5120..9986eb7b379c 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2131,21 +2131,10 @@ static bool hvhe_possible(const struct arm64_cpu_capabilities *entry,
 	return arm64_test_sw_feature_override(ARM64_SW_FEATURE_OVERRIDE_HVHE);
 }
 
-bool cpu_supports_bbml2_noabort(void)
+bool cpu_supports_bbml3(void)
 {
-	/*
-	 * We want to allow usage of BBML2 in as wide a range of kernel contexts
-	 * as possible. This list is therefore an allow-list of known-good
-	 * implementations that both support BBML2 and additionally, fulfill the
-	 * extra constraint of never generating TLB conflict aborts when using
-	 * the relaxed BBML2 semantics (such aborts make use of BBML2 in certain
-	 * kernel contexts difficult to prove safe against recursive aborts).
-	 *
-	 * Note that implementations can only be considered "known-good" if their
-	 * implementors attest to the fact that the implementation never raises
-	 * TLB conflict aborts for BBML2 mapping granularity changes.
-	 */
-	static const struct midr_range supports_bbml2_noabort_list[] = {
+	/* CPUs that support BBML3 but dont advertise through MMFR2 ID */
+	static const struct midr_range supports_bbml3_list[] = {
 		MIDR_REV_RANGE(MIDR_CORTEX_X4, 0, 3, 0xf),
 		MIDR_REV_RANGE(MIDR_NEOVERSE_V3, 0, 2, 0xf),
 		MIDR_REV_RANGE(MIDR_NEOVERSE_V3AE, 0, 2, 0xf),
@@ -2155,8 +2144,7 @@ bool cpu_supports_bbml2_noabort(void)
 		{}
 	};
 
-	/* Does our cpu guarantee to never raise TLB conflict aborts? */
-	if (!is_midr_in_range_list(supports_bbml2_noabort_list))
+	if (!is_midr_in_range_list(supports_bbml3_list))
 		return false;
 
 	/*
@@ -2167,9 +2155,9 @@ bool cpu_supports_bbml2_noabort(void)
 	return true;
 }
 
-static bool has_bbml2_noabort(const struct arm64_cpu_capabilities *caps, int scope)
+static bool has_bbml3(const struct arm64_cpu_capabilities *caps, int scope)
 {
-	return cpu_supports_bbml2_noabort();
+	return cpu_supports_bbml3();
 }
 
 static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused)
@@ -3062,10 +3050,10 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		ARM64_CPUID_FIELDS(ID_AA64MMFR2_EL1, EVT, IMP)
 	},
 	{
-		.desc = "BBM Level 2 without TLB conflict abort",
-		.capability = ARM64_HAS_BBML2_NOABORT,
+		.desc = "BBM Level 3",
+		.capability = ARM64_HAS_BBML3,
 		.type = ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE,
-		.matches = has_bbml2_noabort,
+		.matches = has_bbml3,
 	},
 	{
 		.desc = "52-bit Virtual Addressing for KVM (LPA2)",
diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
index 2de12656b4d8..0acab179fc1a 100644
--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c
@@ -89,7 +89,7 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr,
 	}
 
 	/*
-	 * On eliding the __tlb_flush_range() under BBML2+noabort:
+	 * On eliding the __tlb_flush_range() under BBML3:
 	 *
 	 * NOTE: Instead of using N=16 as the contiguous block length, we use
 	 *       N=4 for clarity.
@@ -135,7 +135,7 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr,
 	 * contiguous TLB entry, which is a micro-optimisation opportunity,
 	 * but does not affect correctness.
 	 *
-	 * In the BBML2 case, the change is avoiding the intermediate tlbi+dsb.
+	 * In the BBML3 case, the change is avoiding the intermediate tlbi+dsb.
 	 * This means a few things, but notably other PEs will still "see" any
 	 * stale cached TLB entries. This could lead to a "contiguous bit
 	 * misprogramming" issue until the final tlbi+dsb of the changed page,
@@ -158,21 +158,16 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr,
 	 *  are present, and a write is made to this address, do we fault or
 	 *  is the write permitted (via amalgamation)?
 	 *
-	 * The relevant Arm ARM DDI 0487L.a requirements are RNGLXZ and RJQQTC,
-	 * and together state that when BBML1 or BBML2 are implemented, either
-	 * a TLB conflict abort is raised (which we expressly forbid), or will
-	 * "produce an OA, access permissions, and memory attributes that are
-	 * consistent with any of the programmed translation table values".
-	 *
-	 * That is to say, will either raise a TLB conflict, or produce one of
-	 * the cached TLB entries, but never amalgamate.
+	 * With BBML3 implemented, no TLB conflict abort is raised and the OA,
+	 * access permissions and memory attributes produced is one of the cached
+	 * TLB entries, but never amalgamate.
 	 *
 	 * Thus, as the page tables are only considered "consistent" after
 	 * the final tlbi+dsb (which evicts both the single stale (RW,n) TLB
 	 * entry as well as the new contiguous (RO,c) TLB entry), omitting the
 	 * initial tlbi+dsb is correct.
 	 *
-	 * It is also important to note that at the end of the BBML2 folding
+	 * It is also important to note that at the end of the BBML3 folding
 	 * case, we are still left with potentially all N TLB entries still
 	 * cached (the N-1 non-contiguous ptes, and the single contiguous
 	 * block). However, over time, natural TLB pressure will cause the
@@ -214,7 +209,7 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr,
 	 *
 	 *                  |____| <--- tlbi + dsb
 	 *
-	 * For BBML2, we again remove the intermediate tlbi+dsb. Here, there
+	 * For BBML3, we again remove the intermediate tlbi+dsb. Here, there
 	 * are no issues, as the final tlbi+dsb covering the changed page is
 	 * guaranteed to remove the original large contiguous (RW,c) TLB entry,
 	 * as well as the intermediate (RW,n) TLB entry; the next access will
@@ -224,7 +219,7 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr,
 	 * regardless.
 	 */
 
-	if (!system_supports_bbml2_noabort())
+	if (!system_supports_bbml3())
 		__flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, 3,
 				  TLBF_NOWALKCACHE);
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index f2be501468ce..d94a049480b1 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -779,18 +779,18 @@ static int split_kernel_leaf_mapping_locked(unsigned long addr)
 
 static inline bool force_pte_mapping(void)
 {
-	const bool bbml2 = system_capabilities_finalized() ?
-		system_supports_bbml2_noabort() : cpu_supports_bbml2_noabort();
+	const bool bbml3 = system_capabilities_finalized() ?
+		system_supports_bbml3() : cpu_supports_bbml3();
 
 	if (debug_pagealloc_enabled())
 		return true;
-	if (bbml2)
+	if (bbml3)
 		return false;
 	return rodata_full || arm64_kfence_can_set_direct_map() || is_realm_world();
 }
 
 static DEFINE_MUTEX(pgtable_split_lock);
-static bool linear_map_requires_bbml2;
+static bool linear_map_requires_bbml3;
 
 int split_kernel_leaf_mapping(unsigned long start, unsigned long end)
 {
@@ -803,15 +803,15 @@ int split_kernel_leaf_mapping(unsigned long start, unsigned long end)
 	 * always pte-mapped), we must not go any further because taking the
 	 * mutex below may sleep. Do not call force_pte_mapping() here because
 	 * it could return a confusing result if called from a secondary cpu
-	 * prior to finalizing caps. Instead, linear_map_requires_bbml2 gives us
+	 * prior to finalizing caps. Instead, linear_map_requires_bbml3 gives us
 	 * what we need.
 	 */
-	if (!linear_map_requires_bbml2 || is_kfence_address((void *)start))
+	if (!linear_map_requires_bbml3 || is_kfence_address((void *)start))
 		return 0;
 
-	if (!system_supports_bbml2_noabort()) {
+	if (!system_supports_bbml3()) {
 		/*
-		 * !BBML2_NOABORT systems should not be trying to change
+		 * BBML3 systems should not be trying to change
 		 * permissions on anything that is not pte-mapped in the first
 		 * place. Just return early and let the permission change code
 		 * raise a warning if not already pte-mapped.
@@ -828,7 +828,7 @@ int split_kernel_leaf_mapping(unsigned long start, unsigned long end)
 
 		/*
 		 * Boot-time: Started secondary cpus but don't know if they
-		 * support BBML2_NOABORT yet. Can't allow splitting in this
+		 * support BBML3 yet. Can't allow splitting in this
 		 * window in case they don't.
 		 */
 		if (WARN_ON(num_online_cpus() > 1))
@@ -934,11 +934,11 @@ static int range_split_to_ptes(unsigned long start, unsigned long end, gfp_t gfp
 	return ret;
 }
 
-u32 idmap_kpti_bbml2_flag;
+u32 idmap_kpti_bbml3_flag;
 
-static void __init init_idmap_kpti_bbml2_flag(void)
+static void __init init_idmap_kpti_bbml3_flag(void)
 {
-	WRITE_ONCE(idmap_kpti_bbml2_flag, 1);
+	WRITE_ONCE(idmap_kpti_bbml3_flag, 1);
 	/* Must be visible to other CPUs before stop_machine() is called. */
 	smp_mb();
 }
@@ -947,7 +947,7 @@ static int __init linear_map_split_to_ptes(void *__unused)
 {
 	/*
 	 * Repainting the linear map must be done by CPU0 (the boot CPU) because
-	 * that's the only CPU that we know supports BBML2. The other CPUs will
+	 * that's the only CPU that we know supports BBML3. The other CPUs will
 	 * be held in a waiting area with the idmap active.
 	 */
 	if (!smp_processor_id()) {
@@ -960,7 +960,7 @@ static int __init linear_map_split_to_ptes(void *__unused)
 		/*
 		 * Wait for all secondary CPUs to be put into the waiting area.
 		 */
-		smp_cond_load_acquire(&idmap_kpti_bbml2_flag, VAL == num_online_cpus());
+		smp_cond_load_acquire(&idmap_kpti_bbml3_flag, VAL == num_online_cpus());
 
 		/*
 		 * Walk all of the linear map [lstart, lend), except the kernel
@@ -979,7 +979,7 @@ static int __init linear_map_split_to_ptes(void *__unused)
 		 * Relies on dsb in flush_tlb_kernel_range() to avoid reordering
 		 * before any page table split operations.
 		 */
-		WRITE_ONCE(idmap_kpti_bbml2_flag, 0);
+		WRITE_ONCE(idmap_kpti_bbml3_flag, 0);
 	} else {
 		typedef void (wait_split_fn)(void);
 		extern wait_split_fn wait_linear_map_split_to_ptes;
@@ -988,7 +988,7 @@ static int __init linear_map_split_to_ptes(void *__unused)
 		wait_fn = (void *)__pa_symbol(wait_linear_map_split_to_ptes);
 
 		/*
-		 * At least one secondary CPU doesn't support BBML2 so cannot
+		 * At least one secondary CPU doesn't support BBML3 so cannot
 		 * tolerate the size of the live mappings changing. So have the
 		 * secondary CPUs wait for the boot CPU to make the changes
 		 * with the idmap active and init_mm inactive.
@@ -1003,8 +1003,8 @@ static int __init linear_map_split_to_ptes(void *__unused)
 
 void __init linear_map_maybe_split_to_ptes(void)
 {
-	if (linear_map_requires_bbml2 && !system_supports_bbml2_noabort()) {
-		init_idmap_kpti_bbml2_flag();
+	if (linear_map_requires_bbml3 && !system_supports_bbml3()) {
+		init_idmap_kpti_bbml3_flag();
 		stop_machine(linear_map_split_to_ptes, NULL, cpu_online_mask);
 	}
 }
@@ -1127,7 +1127,7 @@ bool arch_kfence_init_pool(void)
 	mutex_unlock(&pgtable_split_lock);
 
 	/*
-	 * Since the system supports bbml2_noabort, tlb invalidation is not
+	 * Since the system supports bbml3, tlb invalidation is not
 	 * required here; the pgtable mappings have been split to pte but larger
 	 * entries may safely linger in the TLB.
 	 */
@@ -1166,7 +1166,7 @@ static void __init map_mem(void)
 
 	arm64_kfence_map_pool();
 
-	linear_map_requires_bbml2 = !force_pte_mapping() && can_set_direct_map();
+	linear_map_requires_bbml3 = !force_pte_mapping() && can_set_direct_map();
 
 	if (force_pte_mapping())
 		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
@@ -1333,7 +1333,7 @@ void __init kpti_install_ng_mappings(void)
 	if (arm64_use_ng_mappings)
 		return;
 
-	init_idmap_kpti_bbml2_flag();
+	init_idmap_kpti_bbml3_flag();
 	stop_machine(__kpti_install_ng_mappings, NULL, cpu_online_mask);
 }
 
@@ -1394,7 +1394,7 @@ void __pi_map_range(phys_addr_t *pte, u64 start, u64 end, phys_addr_t pa,
 		    u64 va_offset);
 
 static u8 idmap_ptes[IDMAP_LEVELS - 1][PAGE_SIZE] __aligned(PAGE_SIZE) __ro_after_init,
-	  kpti_bbml2_ptes[IDMAP_LEVELS - 1][PAGE_SIZE] __aligned(PAGE_SIZE) __ro_after_init;
+	  kpti_bbml3_ptes[IDMAP_LEVELS - 1][PAGE_SIZE] __aligned(PAGE_SIZE) __ro_after_init;
 
 static void __init create_idmap(void)
 {
@@ -1406,17 +1406,17 @@ static void __init create_idmap(void)
 		       IDMAP_ROOT_LEVEL, (pte_t *)idmap_pg_dir, false,
 		       __phys_to_virt(ptep) - ptep);
 
-	if (linear_map_requires_bbml2 ||
+	if (linear_map_requires_bbml3 ||
 	    (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0) && !arm64_use_ng_mappings)) {
-		phys_addr_t pa = __pa_symbol(&idmap_kpti_bbml2_flag);
+		phys_addr_t pa = __pa_symbol(&idmap_kpti_bbml3_flag);
 
 		/*
 		 * The KPTI G-to-nG conversion code needs a read-write mapping
 		 * of its synchronization flag in the ID map. This is also used
 		 * when splitting the linear map to ptes if a secondary CPU
-		 * doesn't support bbml2.
+		 * doesn't support bbml3.
 		 */
-		ptep = __pa_symbol(kpti_bbml2_ptes);
+		ptep = __pa_symbol(kpti_bbml3_ptes);
 		__pi_map_range(&ptep, pa, pa + sizeof(u32), pa, PAGE_KERNEL,
 			       IDMAP_ROOT_LEVEL, (pte_t *)idmap_pg_dir, false,
 			       __phys_to_virt(ptep) - ptep);
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 22866b49be37..f4e4e71a0ea8 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -287,7 +287,7 @@ SYM_TYPED_FUNC_START(idmap_kpti_install_ng_mappings)
 
 	mov	x5, x3				// preserve temp_pte arg
 	mrs	swapper_ttb, ttbr1_el1
-	adr_l	flag_ptr, idmap_kpti_bbml2_flag
+	adr_l	flag_ptr, idmap_kpti_bbml3_flag
 
 	cbnz	cpu, __idmap_kpti_secondary
 
@@ -445,7 +445,7 @@ SYM_TYPED_FUNC_START(wait_linear_map_split_to_ptes)
 	flag_ptr	.req	x4
 
 	mrs     swapper_ttb, ttbr1_el1
-	adr_l   flag_ptr, idmap_kpti_bbml2_flag
+	adr_l   flag_ptr, idmap_kpti_bbml3_flag
 	__idmap_cpu_set_reserved_ttbr1 x16, x17
 
 scondary_cpu_wait:
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 9b85a84f6fd4..c05371365d14 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -14,6 +14,7 @@ HAS_ADDRESS_AUTH_ARCH_QARMA5
 HAS_ADDRESS_AUTH_IMP_DEF
 HAS_AMU_EXTN
 HAS_ARMv8_4_TTL
+HAS_BBML3
 HAS_CACHE_DIC
 HAS_CACHE_IDC
 HAS_CNP
@@ -51,7 +52,6 @@ HAS_LS64_V
 HAS_LSUI
 HAS_MOPS
 HAS_NESTED_VIRT
-HAS_BBML2_NOABORT
 HAS_PAN
 HAS_PMUV3
 HAS_S1PIE
-- 
2.43.0