diff options
Diffstat (limited to 'arch/arm/mm/context.c')
| -rw-r--r-- | arch/arm/mm/context.c | 41 |
1 files changed, 24 insertions, 17 deletions
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c index 84e6f772e204..6eb97b3a7481 100644 --- a/arch/arm/mm/context.c +++ b/arch/arm/mm/context.c @@ -36,8 +36,8 @@ * The context ID is used by debuggers and trace logic, and * should be unique within all running processes. * - * In big endian operation, the two 32 bit words are swapped if accesed by - * non 64-bit operations. + * In big endian operation, the two 32 bit words are swapped if accessed + * by non-64-bit operations. */ #define ASID_FIRST_VERSION (1ULL << ASID_BITS) #define NUM_USER_ASIDS ASID_FIRST_VERSION @@ -78,20 +78,21 @@ void a15_erratum_get_cpumask(int this_cpu, struct mm_struct *mm, #endif #ifdef CONFIG_ARM_LPAE -static void cpu_set_reserved_ttbr0(void) -{ - /* - * Set TTBR0 to swapper_pg_dir which contains only global entries. The - * ASID is set to 0. - */ - cpu_set_ttbr(0, __pa(swapper_pg_dir)); - isb(); -} +/* + * With LPAE, the ASID and page tables are updated atomicly, so there is + * no need for a reserved set of tables (the active ASID tracking prevents + * any issues across a rollover). + */ +#define cpu_set_reserved_ttbr0() #else static void cpu_set_reserved_ttbr0(void) { u32 ttb; - /* Copy TTBR1 into TTBR0 */ + /* + * Copy TTBR1 into TTBR0. + * This points at swapper_pg_dir, which contains only global + * entries so any speculative walks are perfectly safe. + */ asm volatile( " mrc p15, 0, %0, c2, c0, 1 @ read TTBR1\n" " mcr p15, 0, %0, c2, c0, 0 @ set TTBR0\n" @@ -179,6 +180,7 @@ static int is_reserved_asid(u64 asid) static u64 new_context(struct mm_struct *mm, unsigned int cpu) { + static u32 cur_idx = 1; u64 asid = atomic64_read(&mm->context.id); u64 generation = atomic64_read(&asid_generation); @@ -193,10 +195,13 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu) * Allocate a free ASID. If we can't find one, take a * note of the currently active ASIDs and mark the TLBs * as requiring flushes. We always count from ASID #1, - * as we reserve ASID #0 to switch via TTBR0 and indicate - * rollover events. + * as we reserve ASID #0 to switch via TTBR0 and to + * avoid speculative page table walks from hitting in + * any partial walk caches, which could be populated + * from overlapping level-1 descriptors used to map both + * the module area and the userspace stack. */ - asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1); + asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, cur_idx); if (asid == NUM_USER_ASIDS) { generation = atomic64_add_return(ASID_FIRST_VERSION, &asid_generation); @@ -204,6 +209,7 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu) asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1); } __set_bit(asid, asid_map); + cur_idx = asid; asid |= generation; cpumask_clear(mm_cpumask(mm)); } @@ -221,8 +227,9 @@ void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk) __check_vmalloc_seq(mm); /* - * Required during context switch to avoid speculative page table - * walking with the wrong TTBR. + * We cannot update the pgd and the ASID atomicly with classic + * MMU, so switch exclusively to global mappings to avoid + * speculative page table walking with the wrong TTBR. */ cpu_set_reserved_ttbr0(); |
