diff options
Diffstat (limited to 'arch/arm64/mm/context.c')
-rw-r--r-- | arch/arm64/mm/context.c | 221 |
1 files changed, 188 insertions, 33 deletions
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index b5e329fde2dd..188197590fc9 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -6,6 +6,7 @@ * Copyright (C) 2012 ARM Ltd. */ +#include <linux/bitfield.h> #include <linux/bitops.h> #include <linux/sched.h> #include <linux/slab.h> @@ -26,35 +27,33 @@ static DEFINE_PER_CPU(atomic64_t, active_asids); static DEFINE_PER_CPU(u64, reserved_asids); static cpumask_t tlb_flush_pending; +static unsigned long max_pinned_asids; +static unsigned long nr_pinned_asids; +static unsigned long *pinned_asid_map; + #define ASID_MASK (~GENMASK(asid_bits - 1, 0)) #define ASID_FIRST_VERSION (1UL << asid_bits) -#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 -#define NUM_USER_ASIDS (ASID_FIRST_VERSION >> 1) -#define asid2idx(asid) (((asid) & ~ASID_MASK) >> 1) -#define idx2asid(idx) (((idx) << 1) & ~ASID_MASK) -#else -#define NUM_USER_ASIDS (ASID_FIRST_VERSION) -#define asid2idx(asid) ((asid) & ~ASID_MASK) -#define idx2asid(idx) asid2idx(idx) -#endif +#define NUM_USER_ASIDS ASID_FIRST_VERSION +#define ctxid2asid(asid) ((asid) & ~ASID_MASK) +#define asid2ctxid(asid, genid) ((asid) | (genid)) /* Get the ASIDBits supported by the current CPU */ static u32 get_cpu_asid_bits(void) { u32 asid; int fld = cpuid_feature_extract_unsigned_field(read_cpuid(ID_AA64MMFR0_EL1), - ID_AA64MMFR0_ASID_SHIFT); + ID_AA64MMFR0_EL1_ASIDBITS_SHIFT); switch (fld) { default: pr_warn("CPU%d: Unknown ASID size (%d); assuming 8-bit\n", smp_processor_id(), fld); - /* Fallthrough */ - case 0: + fallthrough; + case ID_AA64MMFR0_EL1_ASIDBITS_8: asid = 8; break; - case 2: + case ID_AA64MMFR0_EL1_ASIDBITS_16: asid = 16; } @@ -77,13 +76,38 @@ void verify_cpu_asid_bits(void) } } +static void set_kpti_asid_bits(unsigned long *map) +{ + unsigned int len = BITS_TO_LONGS(NUM_USER_ASIDS) * sizeof(unsigned long); + /* + * In case of KPTI kernel/user ASIDs are allocated in + * pairs, the bottom bit distinguishes the two: if it + * is set, then the ASID will map only userspace. Thus + * mark even as reserved for kernel. + */ + memset(map, 0xaa, len); +} + +static void set_reserved_asid_bits(void) +{ + if (pinned_asid_map) + bitmap_copy(asid_map, pinned_asid_map, NUM_USER_ASIDS); + else if (arm64_kernel_unmapped_at_el0()) + set_kpti_asid_bits(asid_map); + else + bitmap_clear(asid_map, 0, NUM_USER_ASIDS); +} + +#define asid_gen_match(asid) \ + (!(((asid) ^ atomic64_read(&asid_generation)) >> asid_bits)) + static void flush_context(void) { int i; u64 asid; /* Update the list of reserved ASIDs and the ASID bitmap. */ - bitmap_clear(asid_map, 0, NUM_USER_ASIDS); + set_reserved_asid_bits(); for_each_possible_cpu(i) { asid = atomic64_xchg_relaxed(&per_cpu(active_asids, i), 0); @@ -96,7 +120,7 @@ static void flush_context(void) */ if (asid == 0) asid = per_cpu(reserved_asids, i); - __set_bit(asid2idx(asid), asid_map); + __set_bit(ctxid2asid(asid), asid_map); per_cpu(reserved_asids, i) = asid; } @@ -138,7 +162,7 @@ static u64 new_context(struct mm_struct *mm) u64 generation = atomic64_read(&asid_generation); if (asid != 0) { - u64 newasid = generation | (asid & ~ASID_MASK); + u64 newasid = asid2ctxid(ctxid2asid(asid), generation); /* * If our current ASID was active during a rollover, we @@ -148,10 +172,18 @@ static u64 new_context(struct mm_struct *mm) return newasid; /* + * If it is pinned, we can keep using it. Note that reserved + * takes priority, because even if it is also pinned, we need to + * update the generation into the reserved_asids. + */ + if (refcount_read(&mm->context.pinned)) + return newasid; + + /* * We had a valid ASID in a previous life, so try to re-use * it if possible. */ - if (!__test_and_set_bit(asid2idx(asid), asid_map)) + if (!__test_and_set_bit(ctxid2asid(asid), asid_map)) return newasid; } @@ -177,12 +209,13 @@ static u64 new_context(struct mm_struct *mm) set_asid: __set_bit(asid, asid_map); cur_idx = asid; - return idx2asid(asid) | generation; + return asid2ctxid(asid, generation); } -void check_and_switch_context(struct mm_struct *mm, unsigned int cpu) +void check_and_switch_context(struct mm_struct *mm) { unsigned long flags; + unsigned int cpu; u64 asid, old_active_asid; if (system_supports_cnp()) @@ -204,25 +237,25 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu) * relaxed xchg in flush_context will treat us as reserved * because atomic RmWs are totally ordered for a given location. */ - old_active_asid = atomic64_read(&per_cpu(active_asids, cpu)); - if (old_active_asid && - !((asid ^ atomic64_read(&asid_generation)) >> asid_bits) && - atomic64_cmpxchg_relaxed(&per_cpu(active_asids, cpu), + old_active_asid = atomic64_read(this_cpu_ptr(&active_asids)); + if (old_active_asid && asid_gen_match(asid) && + atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_asids), old_active_asid, asid)) goto switch_mm_fastpath; raw_spin_lock_irqsave(&cpu_asid_lock, flags); /* Check that our ASID belongs to the current generation. */ asid = atomic64_read(&mm->context.id); - if ((asid ^ atomic64_read(&asid_generation)) >> asid_bits) { + if (!asid_gen_match(asid)) { asid = new_context(mm); atomic64_set(&mm->context.id, asid); } + cpu = smp_processor_id(); if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) local_flush_tlb_all(); - atomic64_set(&per_cpu(active_asids, cpu), asid); + atomic64_set(this_cpu_ptr(&active_asids), asid); raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); switch_mm_fastpath: @@ -237,31 +270,153 @@ switch_mm_fastpath: cpu_switch_mm(mm->pgd, mm); } +unsigned long arm64_mm_context_get(struct mm_struct *mm) +{ + unsigned long flags; + u64 asid; + + if (!pinned_asid_map) + return 0; + + raw_spin_lock_irqsave(&cpu_asid_lock, flags); + + asid = atomic64_read(&mm->context.id); + + if (refcount_inc_not_zero(&mm->context.pinned)) + goto out_unlock; + + if (nr_pinned_asids >= max_pinned_asids) { + asid = 0; + goto out_unlock; + } + + if (!asid_gen_match(asid)) { + /* + * We went through one or more rollover since that ASID was + * used. Ensure that it is still valid, or generate a new one. + */ + asid = new_context(mm); + atomic64_set(&mm->context.id, asid); + } + + nr_pinned_asids++; + __set_bit(ctxid2asid(asid), pinned_asid_map); + refcount_set(&mm->context.pinned, 1); + +out_unlock: + raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); + + asid = ctxid2asid(asid); + + /* Set the equivalent of USER_ASID_BIT */ + if (asid && arm64_kernel_unmapped_at_el0()) + asid |= 1; + + return asid; +} +EXPORT_SYMBOL_GPL(arm64_mm_context_get); + +void arm64_mm_context_put(struct mm_struct *mm) +{ + unsigned long flags; + u64 asid = atomic64_read(&mm->context.id); + + if (!pinned_asid_map) + return; + + raw_spin_lock_irqsave(&cpu_asid_lock, flags); + + if (refcount_dec_and_test(&mm->context.pinned)) { + __clear_bit(ctxid2asid(asid), pinned_asid_map); + nr_pinned_asids--; + } + + raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); +} +EXPORT_SYMBOL_GPL(arm64_mm_context_put); + /* Errata workaround post TTBRx_EL1 update. */ asmlinkage void post_ttbr_update_workaround(void) { + if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) + return; + asm(ALTERNATIVE("nop; nop; nop", "ic iallu; dsb nsh; isb", - ARM64_WORKAROUND_CAVIUM_27456, - CONFIG_CAVIUM_ERRATUM_27456)); + ARM64_WORKAROUND_CAVIUM_27456)); } -static int asids_init(void) +void cpu_do_switch_mm(phys_addr_t pgd_phys, struct mm_struct *mm) { - asid_bits = get_cpu_asid_bits(); + unsigned long ttbr1 = read_sysreg(ttbr1_el1); + unsigned long asid = ASID(mm); + unsigned long ttbr0 = phys_to_ttbr(pgd_phys); + + /* Skip CNP for the reserved ASID */ + if (system_supports_cnp() && asid) + ttbr0 |= TTBR_CNP_BIT; + + /* SW PAN needs a copy of the ASID in TTBR0 for entry */ + if (IS_ENABLED(CONFIG_ARM64_SW_TTBR0_PAN)) + ttbr0 |= FIELD_PREP(TTBR_ASID_MASK, asid); + + /* Set ASID in TTBR1 since TCR.A1 is set */ + ttbr1 &= ~TTBR_ASID_MASK; + ttbr1 |= FIELD_PREP(TTBR_ASID_MASK, asid); + + cpu_set_reserved_ttbr0_nosync(); + write_sysreg(ttbr1, ttbr1_el1); + write_sysreg(ttbr0, ttbr0_el1); + isb(); + post_ttbr_update_workaround(); +} + +static int asids_update_limit(void) +{ + unsigned long num_available_asids = NUM_USER_ASIDS; + + if (arm64_kernel_unmapped_at_el0()) { + num_available_asids /= 2; + if (pinned_asid_map) + set_kpti_asid_bits(pinned_asid_map); + } /* * Expect allocation after rollover to fail if we don't have at least * one more ASID than CPUs. ASID #0 is reserved for init_mm. */ - WARN_ON(NUM_USER_ASIDS - 1 <= num_possible_cpus()); + WARN_ON(num_available_asids - 1 <= num_possible_cpus()); + pr_info("ASID allocator initialised with %lu entries\n", + num_available_asids); + + /* + * There must always be an ASID available after rollover. Ensure that, + * even if all CPUs have a reserved ASID and the maximum number of ASIDs + * are pinned, there still is at least one empty slot in the ASID map. + */ + max_pinned_asids = num_available_asids - num_possible_cpus() - 2; + return 0; +} +arch_initcall(asids_update_limit); + +static int asids_init(void) +{ + asid_bits = get_cpu_asid_bits(); atomic64_set(&asid_generation, ASID_FIRST_VERSION); - asid_map = kcalloc(BITS_TO_LONGS(NUM_USER_ASIDS), sizeof(*asid_map), - GFP_KERNEL); + asid_map = bitmap_zalloc(NUM_USER_ASIDS, GFP_KERNEL); if (!asid_map) panic("Failed to allocate bitmap for %lu ASIDs\n", NUM_USER_ASIDS); - pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS); + pinned_asid_map = bitmap_zalloc(NUM_USER_ASIDS, GFP_KERNEL); + nr_pinned_asids = 0; + + /* + * We cannot call set_reserved_asid_bits() here because CPU + * caps are not finalized yet, so it is safer to assume KPTI + * and reserve kernel ASID's from beginning. + */ + if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) + set_kpti_asid_bits(asid_map); return 0; } early_initcall(asids_init); |