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Date: Thu, 31 Jan 2013 23:18:36 -0500 (EST)
From: Nicolas Pitre <nicolas.pitre@...aro.org>
To: Joonsoo Kim <iamjoonsoo.kim@....com>
cc: Russell King <linux@....linux.org.uk>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
js1304@...il.com, Will Deacon <will.deacon@....com>,
Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v4 3/3] ARM: mm: use static_vm for managing static mapped
areas
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@....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.
> + 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.
> - 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
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