[PATCH v4 3/3] ARM: mm: use static_vm for managing static mapped areas

[JoonSoo Kim]

2013/2/1 Nicolas Pitre <nicolas.pitre at linaro.org>:
> On Thu, 31 Jan 2013, Joonsoo Kim wrote:
>
>> A static mapped area is ARM-specific, so it is better not to use
>> generic vmalloc data structure, that is, vmlist and vmlist_lock
>> for managing static mapped area. And it causes some needless overhead and
>> reducing this overhead is better idea.
>>
>> Now, we have newly introduced static_vm infrastructure.
>> With it, we don't need to iterate all mapped areas. Instead, we just
>> iterate static mapped areas. It helps to reduce an overhead of finding
>> matched area. And architecture dependency on vmalloc layer is removed,
>> so it will help to maintainability for vmalloc layer.
>>
>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim at lge.com>
>
> Comments below.
>
>>
>> diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
>> index ceb34ae..7fe5b48 100644
>> --- a/arch/arm/mm/ioremap.c
>> +++ b/arch/arm/mm/ioremap.c
>> @@ -269,13 +269,14 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
>>       const struct mem_type *type;
>>       int err;
>>       unsigned long addr;
>> -     struct vm_struct * area;
>> +     struct vm_struct *area;
>> +     phys_addr_t paddr = __pfn_to_phys(pfn);
>>
>>  #ifndef CONFIG_ARM_LPAE
>>       /*
>>        * High mappings must be supersection aligned
>>        */
>> -     if (pfn >= 0x100000 && (__pfn_to_phys(pfn) & ~SUPERSECTION_MASK))
>> +     if (pfn >= 0x100000 && (paddr & ~SUPERSECTION_MASK))
>>               return NULL;
>>  #endif
>>
>> @@ -291,24 +292,17 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
>>       /*
>>        * Try to reuse one of the static mapping whenever possible.
>>        */
>> -     read_lock(&vmlist_lock);
>> -     for (area = vmlist; area; area = area->next) {
>> -             if (!size || (sizeof(phys_addr_t) == 4 && pfn >= 0x100000))
>> -                     break;
>> -             if (!(area->flags & VM_ARM_STATIC_MAPPING))
>> -                     continue;
>> -             if ((area->flags & VM_ARM_MTYPE_MASK) != VM_ARM_MTYPE(mtype))
>> -                     continue;
>> -             if (__phys_to_pfn(area->phys_addr) > pfn ||
>> -                 __pfn_to_phys(pfn) + size-1 > area->phys_addr + area->size-1)
>> -                     continue;
>> -             /* we can drop the lock here as we know *area is static */
>> -             read_unlock(&vmlist_lock);
>> -             addr = (unsigned long)area->addr;
>> -             addr += __pfn_to_phys(pfn) - area->phys_addr;
>> -             return (void __iomem *) (offset + addr);
>> +     if (size && !((sizeof(phys_addr_t) == 4 && pfn >= 0x100000))) {
>> +             struct static_vm *svm;
>> +
>> +             svm = find_static_vm_paddr(paddr, size,
>> +                             STATIC_VM_TYPE(STATIC_VM_MEM, mtype));
>> +             if (svm) {
>> +                     addr = (unsigned long)svm->vm.addr;
>> +                     addr += paddr - svm->vm.phys_addr;
>> +                     return (void __iomem *) (offset + addr);
>> +             }
>>       }
>> -     read_unlock(&vmlist_lock);
>>
>>       /*
>>        * Don't allow RAM to be mapped - this causes problems with ARMv6+
>> @@ -320,21 +314,21 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
>>       if (!area)
>>               return NULL;
>>       addr = (unsigned long)area->addr;
>> -     area->phys_addr = __pfn_to_phys(pfn);
>> +     area->phys_addr = paddr;
>>
>>  #if !defined(CONFIG_SMP) && !defined(CONFIG_ARM_LPAE)
>>       if (DOMAIN_IO == 0 &&
>>           (((cpu_architecture() >= CPU_ARCH_ARMv6) && (get_cr() & CR_XP)) ||
>>              cpu_is_xsc3()) && pfn >= 0x100000 &&
>> -            !((__pfn_to_phys(pfn) | size | addr) & ~SUPERSECTION_MASK)) {
>> +            !((paddr | size | addr) & ~SUPERSECTION_MASK)) {
>>               area->flags |= VM_ARM_SECTION_MAPPING;
>>               err = remap_area_supersections(addr, pfn, size, type);
>> -     } else if (!((__pfn_to_phys(pfn) | size | addr) & ~PMD_MASK)) {
>> +     } else if (!((paddr | size | addr) & ~PMD_MASK)) {
>>               area->flags |= VM_ARM_SECTION_MAPPING;
>>               err = remap_area_sections(addr, pfn, size, type);
>>       } else
>>  #endif
>> -             err = ioremap_page_range(addr, addr + size, __pfn_to_phys(pfn),
>> +             err = ioremap_page_range(addr, addr + size, paddr,
>>                                        __pgprot(type->prot_pte));
>>
>>       if (err) {
>> @@ -418,34 +412,21 @@ __arm_ioremap_exec(unsigned long phys_addr, size_t size, bool cached)
>>  void __iounmap(volatile void __iomem *io_addr)
>>  {
>>       void *addr = (void *)(PAGE_MASK & (unsigned long)io_addr);
>> -     struct vm_struct *vm;
>> +     struct static_vm *svm;
>> +
>
> You could salvage the "/* If this is a static mapping we must leave it
> alone */" comment here.

Okay.

>> +     svm = find_static_vm_vaddr(addr);
>> +     if (svm)
>> +             return;
>>
>> -     read_lock(&vmlist_lock);
>> -     for (vm = vmlist; vm; vm = vm->next) {
>> -             if (vm->addr > addr)
>> -                     break;
>> -             if (!(vm->flags & VM_IOREMAP))
>> -                     continue;
>> -             /* If this is a static mapping we must leave it alone */
>> -             if ((vm->flags & VM_ARM_STATIC_MAPPING) &&
>> -                 (vm->addr <= addr) && (vm->addr + vm->size > addr)) {
>> -                     read_unlock(&vmlist_lock);
>> -                     return;
>> -             }
>>  #if !defined(CONFIG_SMP) && !defined(CONFIG_ARM_LPAE)
>> -             /*
>> -              * If this is a section based mapping we need to handle it
>> -              * specially as the VM subsystem does not know how to handle
>> -              * such a beast.
>> -              */
>
> Please don't remove the above comment.  It is still relevant.

Yes.

Thanks for comments.

>> -             if ((vm->addr == addr) &&
>> -                 (vm->flags & VM_ARM_SECTION_MAPPING)) {
>> +     {
>> +             struct vm_struct *vm;
>> +
>> +             vm = find_vm_area(addr);
>> +             if (vm && (vm->flags & VM_ARM_SECTION_MAPPING))
>>                       unmap_area_sections((unsigned long)vm->addr, vm->size);
>> -                     break;
>> -             }
>> -#endif
>>       }
>> -     read_unlock(&vmlist_lock);
>> +#endif
>>
>>       vunmap(addr);
>>  }
>> diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
>> index fb45c79..24c1df4 100644
>> --- a/arch/arm/mm/mm.h
>> +++ b/arch/arm/mm/mm.h
>> @@ -54,16 +54,6 @@ extern void __flush_dcache_page(struct address_space *mapping, struct page *page
>>  /* (super)section-mapped I/O regions used by ioremap()/iounmap() */
>>  #define VM_ARM_SECTION_MAPPING       0x80000000
>>
>> -/* permanent static mappings from iotable_init() */
>> -#define VM_ARM_STATIC_MAPPING        0x40000000
>> -
>> -/* empty mapping */
>> -#define VM_ARM_EMPTY_MAPPING 0x20000000
>> -
>> -/* mapping type (attributes) for permanent static mappings */
>> -#define VM_ARM_MTYPE(mt)             ((mt) << 20)
>> -#define VM_ARM_MTYPE_MASK    (0x1f << 20)
>> -
>
> This goes with a related question in my previous email: why didn't you
> keep those flags as they were?
>
>
> Nicolas