Re: [PATCHv4 2/2] ARM: dma-mapping: remove custom consistent dmaregion
From: Minchan Kim
Date: Tue Jun 26 2012 - 21:55:21 EST
On 06/25/2012 05:47 PM, Marek Szyprowski wrote:
> This patch changes dma-mapping subsystem to use generic vmalloc areas
> for all consistent dma allocations. This increases the total size limit
> of the consistent allocations and removes platform hacks and a lot of
> duplicated code.
>
> Atomic allocations are served from special pool preallocated on boot,
> becasue vmalloc areas cannot be reliably created in atomic context.
s/becasue/because
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Reviewed-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
I like this patch very much but notice one more again.
Here is goes, again.
https://lkml.org/lkml/2012/6/13/628
It's another hack for avoding vmalloc atomic.
There are several grumblers ago and everybody made own mempool so code
began to bloat and it would be error-prone. :(
I think it's TODO for mm folks to decide.
Anyway, there are some trivial comment below.
> ---
> Documentation/kernel-parameters.txt | 2 +-
> arch/arm/include/asm/dma-mapping.h | 2 +-
> arch/arm/mm/dma-mapping.c | 505 +++++++++++++----------------------
> arch/arm/mm/mm.h | 3 +
> include/linux/vmalloc.h | 1 +
> mm/vmalloc.c | 10 +-
> 6 files changed, 194 insertions(+), 329 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index a92c5eb..da07f6c 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -526,7 +526,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>
> coherent_pool=nn[KMG] [ARM,KNL]
> Sets the size of memory pool for coherent, atomic dma
> - allocations if Contiguous Memory Allocator (CMA) is used.
> + allocations.
What's the default? 256K?
If we specify, couldn't it help?
>
> code_bytes [X86] How many bytes of object code to print
> in an oops report.
> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> index bbef15d..80777d87 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -226,7 +226,7 @@ static inline int dma_mmap_writecombine(struct device *dev, struct vm_area_struc
> * DMA region above it's default value of 2MB. It must be called before the
> * memory allocator is initialised, i.e. before any core_initcall.
> */
> -extern void __init init_consistent_dma_size(unsigned long size);
> +static inline void init_consistent_dma_size(unsigned long size) { }
>
> /*
> * For SA-1111, IXP425, and ADI systems the dma-mapping functions are "magic"
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index d766e42..c1f2294 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -22,6 +22,7 @@
> #include <linux/memblock.h>
> #include <linux/slab.h>
> #include <linux/iommu.h>
> +#include <linux/io.h>
> #include <linux/vmalloc.h>
>
> #include <asm/memory.h>
> @@ -217,115 +218,67 @@ static void __dma_free_buffer(struct page *page, size_t size)
> }
>
> #ifdef CONFIG_MMU
> -
> -#define CONSISTENT_OFFSET(x) (((unsigned long)(x) - consistent_base) >> PAGE_SHIFT)
> -#define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - consistent_base) >> PMD_SHIFT)
> -
> -/*
> - * These are the page tables (2MB each) covering uncached, DMA consistent allocations
> - */
> -static pte_t **consistent_pte;
> -
> -#define DEFAULT_CONSISTENT_DMA_SIZE SZ_2M
> -
> -static unsigned long consistent_base = CONSISTENT_END - DEFAULT_CONSISTENT_DMA_SIZE;
> -
> -void __init init_consistent_dma_size(unsigned long size)
> -{
> - unsigned long base = CONSISTENT_END - ALIGN(size, SZ_2M);
> -
> - BUG_ON(consistent_pte); /* Check we're called before DMA region init */
> - BUG_ON(base < VMALLOC_END);
> -
> - /* Grow region to accommodate specified size */
> - if (base < consistent_base)
> - consistent_base = base;
> -}
> -
> -#include "vmregion.h"
> -
> -static struct arm_vmregion_head consistent_head = {
> - .vm_lock = __SPIN_LOCK_UNLOCKED(&consistent_head.vm_lock),
> - .vm_list = LIST_HEAD_INIT(consistent_head.vm_list),
> - .vm_end = CONSISTENT_END,
> -};
> -
> #ifdef CONFIG_HUGETLB_PAGE
> #error ARM Coherent DMA allocator does not (yet) support huge TLB
> #endif
>
> -/*
> - * Initialise the consistent memory allocation.
> - */
> -static int __init consistent_init(void)
> -{
> - int ret = 0;
> - pgd_t *pgd;
> - pud_t *pud;
> - pmd_t *pmd;
> - pte_t *pte;
> - int i = 0;
> - unsigned long base = consistent_base;
> - unsigned long num_ptes = (CONSISTENT_END - base) >> PMD_SHIFT;
> -
> - if (IS_ENABLED(CONFIG_CMA) && !IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU))
> - return 0;
> -
> - consistent_pte = kmalloc(num_ptes * sizeof(pte_t), GFP_KERNEL);
> - if (!consistent_pte) {
> - pr_err("%s: no memory\n", __func__);
> - return -ENOMEM;
> - }
> -
> - pr_debug("DMA memory: 0x%08lx - 0x%08lx:\n", base, CONSISTENT_END);
> - consistent_head.vm_start = base;
> -
> - do {
> - pgd = pgd_offset(&init_mm, base);
> -
> - pud = pud_alloc(&init_mm, pgd, base);
> - if (!pud) {
> - pr_err("%s: no pud tables\n", __func__);
> - ret = -ENOMEM;
> - break;
> - }
> -
> - pmd = pmd_alloc(&init_mm, pud, base);
> - if (!pmd) {
> - pr_err("%s: no pmd tables\n", __func__);
> - ret = -ENOMEM;
> - break;
> - }
> - WARN_ON(!pmd_none(*pmd));
> -
> - pte = pte_alloc_kernel(pmd, base);
> - if (!pte) {
> - pr_err("%s: no pte tables\n", __func__);
> - ret = -ENOMEM;
> - break;
> - }
> -
> - consistent_pte[i++] = pte;
> - base += PMD_SIZE;
> - } while (base < CONSISTENT_END);
> -
> - return ret;
> -}
> -core_initcall(consistent_init);
> -
> static void *__alloc_from_contiguous(struct device *dev, size_t size,
> pgprot_t prot, struct page **ret_page);
>
> -static struct arm_vmregion_head coherent_head = {
> - .vm_lock = __SPIN_LOCK_UNLOCKED(&coherent_head.vm_lock),
> - .vm_list = LIST_HEAD_INIT(coherent_head.vm_list),
> +static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
> + pgprot_t prot, struct page **ret_page,
> + const void *caller);
> +
> +static void *
> +__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
> + const void *caller)
> +{
> + struct vm_struct *area;
> + unsigned long addr;
> +
> + area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | VM_USERMAP,
> + caller);
Please write down why we always need VM_USERMAP.
If we always need it in ARM, why don't you define following as?
#define VM_ARM_DMA_CONSISTENT (0x20000000 | VM_USERAMP)?
Although it's trivial, it could be more understandable that everybody
can think of it that "ARM DMA allocation could be mapped by user space, everytime"
> + if (!area)
> + return NULL;
> + addr = (unsigned long)area->addr;
> + area->phys_addr = __pfn_to_phys(page_to_pfn(page));
> +
> + if (ioremap_page_range(addr, addr + size, area->phys_addr, prot)) {
> + vunmap((void *)addr);
> + return NULL;
> + }
> + return (void *)addr;
> +}
> +
> +static void __dma_free_remap(void *cpu_addr, size_t size)
> +{
> + struct vm_struct *area = find_vm_area(cpu_addr);
> + if (!area || !(area->flags & VM_ARM_DMA_CONSISTENT)) {
Above definery could enhance this check, too.
> + pr_err("%s: trying to free invalid coherent area: %p\n",
> + __func__, cpu_addr);
> + dump_stack();
> + return;
> + }
> + unmap_kernel_range((unsigned long)cpu_addr, size);
> + vunmap(cpu_addr);
> +}
> +
> +struct dma_pool {
> + size_t size;
> + spinlock_t lock;
> + unsigned long *bitmap;
> + unsigned long nr_pages;
> + void *vaddr;
> + struct page *page;
> };
>
> -static size_t coherent_pool_size = DEFAULT_CONSISTENT_DMA_SIZE / 8;
> +static struct dma_pool atomic_pool = {
> + .size = SZ_256K,
> +};
>
> static int __init early_coherent_pool(char *p)
> {
> - coherent_pool_size = memparse(p, &p);
> + atomic_pool.size = memparse(p, &p);
> return 0;
> }
> early_param("coherent_pool", early_coherent_pool);
> @@ -333,32 +286,45 @@ early_param("coherent_pool", early_coherent_pool);
> /*
> * Initialise the coherent pool for atomic allocations.
> */
> -static int __init coherent_init(void)
> +static int __init atomic_pool_init(void)
> {
> + struct dma_pool *pool = &atomic_pool;
> pgprot_t prot = pgprot_dmacoherent(pgprot_kernel);
> - size_t size = coherent_pool_size;
> + unsigned long nr_pages = pool->size >> PAGE_SHIFT;
> + unsigned long *bitmap;
> struct page *page;
> void *ptr;
> + int bitmap_size = BITS_TO_LONGS(nr_pages) * sizeof(long);
>
> - if (!IS_ENABLED(CONFIG_CMA))
> - return 0;
> + bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> + if (!bitmap)
> + goto no_bitmap;
>
> - ptr = __alloc_from_contiguous(NULL, size, prot, &page);
> + if (IS_ENABLED(CONFIG_CMA))
> + ptr = __alloc_from_contiguous(NULL, pool->size, prot, &page);
> + else
> + ptr = __alloc_remap_buffer(NULL, pool->size, GFP_KERNEL, prot,
> + &page, NULL);
> if (ptr) {
> - coherent_head.vm_start = (unsigned long) ptr;
> - coherent_head.vm_end = (unsigned long) ptr + size;
> - printk(KERN_INFO "DMA: preallocated %u KiB pool for atomic coherent allocations\n",
> - (unsigned)size / 1024);
> + spin_lock_init(&pool->lock);
> + pool->vaddr = ptr;
> + pool->page = page;
> + pool->bitmap = bitmap;
> + pool->nr_pages = nr_pages;
> + pr_info("DMA: preallocated %u KiB pool for atomic coherent allocations\n",
> + (unsigned)pool->size / 1024);
> return 0;
> }
> - printk(KERN_ERR "DMA: failed to allocate %u KiB pool for atomic coherent allocation\n",
> - (unsigned)size / 1024);
> + kfree(bitmap);
> +no_bitmap:
> + pr_err("DMA: failed to allocate %u KiB pool for atomic coherent allocation\n",
> + (unsigned)pool->size / 1024);
> return -ENOMEM;
> }
> /*
> * CMA is activated by core_initcall, so we must be called after it.
> */
> -postcore_initcall(coherent_init);
> +postcore_initcall(atomic_pool_init);
>
> struct dma_contig_early_reserve {
> phys_addr_t base;
> @@ -406,112 +372,6 @@ void __init dma_contiguous_remap(void)
> }
> }
>
> -static void *
> -__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
> - const void *caller)
> -{
> - struct arm_vmregion *c;
> - size_t align;
> - int bit;
> -
> - if (!consistent_pte) {
> - pr_err("%s: not initialised\n", __func__);
> - dump_stack();
> - return NULL;
> - }
> -
> - /*
> - * Align the virtual region allocation - maximum alignment is
> - * a section size, minimum is a page size. This helps reduce
> - * fragmentation of the DMA space, and also prevents allocations
> - * smaller than a section from crossing a section boundary.
> - */
> - bit = fls(size - 1);
> - if (bit > SECTION_SHIFT)
> - bit = SECTION_SHIFT;
> - align = 1 << bit;
> -
> - /*
> - * Allocate a virtual address in the consistent mapping region.
> - */
> - c = arm_vmregion_alloc(&consistent_head, align, size,
> - gfp & ~(__GFP_DMA | __GFP_HIGHMEM), caller);
> - if (c) {
> - pte_t *pte;
> - int idx = CONSISTENT_PTE_INDEX(c->vm_start);
> - u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
> -
> - pte = consistent_pte[idx] + off;
> - c->priv = page;
> -
> - do {
> - BUG_ON(!pte_none(*pte));
> -
> - set_pte_ext(pte, mk_pte(page, prot), 0);
> - page++;
> - pte++;
> - off++;
> - if (off >= PTRS_PER_PTE) {
> - off = 0;
> - pte = consistent_pte[++idx];
> - }
> - } while (size -= PAGE_SIZE);
> -
> - dsb();
> -
> - return (void *)c->vm_start;
> - }
> - return NULL;
> -}
> -
> -static void __dma_free_remap(void *cpu_addr, size_t size)
> -{
> - struct arm_vmregion *c;
> - unsigned long addr;
> - pte_t *ptep;
> - int idx;
> - u32 off;
> -
> - c = arm_vmregion_find_remove(&consistent_head, (unsigned long)cpu_addr);
> - if (!c) {
> - pr_err("%s: trying to free invalid coherent area: %p\n",
> - __func__, cpu_addr);
> - dump_stack();
> - return;
> - }
> -
> - if ((c->vm_end - c->vm_start) != size) {
> - pr_err("%s: freeing wrong coherent size (%ld != %d)\n",
> - __func__, c->vm_end - c->vm_start, size);
> - dump_stack();
> - size = c->vm_end - c->vm_start;
> - }
> -
> - idx = CONSISTENT_PTE_INDEX(c->vm_start);
> - off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
> - ptep = consistent_pte[idx] + off;
> - addr = c->vm_start;
> - do {
> - pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep);
> -
> - ptep++;
> - addr += PAGE_SIZE;
> - off++;
> - if (off >= PTRS_PER_PTE) {
> - off = 0;
> - ptep = consistent_pte[++idx];
> - }
> -
> - if (pte_none(pte) || !pte_present(pte))
> - pr_crit("%s: bad page in kernel page table\n",
> - __func__);
> - } while (size -= PAGE_SIZE);
> -
> - flush_tlb_kernel_range(c->vm_start, c->vm_end);
> -
> - arm_vmregion_free(&consistent_head, c);
> -}
> -
> static int __dma_update_pte(pte_t *pte, pgtable_t token, unsigned long addr,
> void *data)
> {
> @@ -552,15 +412,17 @@ static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
> return ptr;
> }
>
> -static void *__alloc_from_pool(struct device *dev, size_t size,
> - struct page **ret_page, const void *caller)
> +static void *__alloc_from_pool(size_t size, struct page **ret_page)
> {
> - struct arm_vmregion *c;
> + struct dma_pool *pool = &atomic_pool;
> + unsigned int count = size >> PAGE_SHIFT;
Just out of curiosity.
Do we make sure size is always aligned to PAGE_SIZE?
If so, please write down
> + unsigned int pageno;
> + unsigned long flags;
> + void *ptr = NULL;
> size_t align;
>
> - if (!coherent_head.vm_start) {
> - printk(KERN_ERR "%s: coherent pool not initialised!\n",
> - __func__);
> + if (!pool->vaddr) {
> + pr_err("%s: coherent pool not initialised!\n", __func__);
> dump_stack();
Why doesn't you use WARN?
> return NULL;
> }
< snip>
--
Kind regards,
Minchan Kim
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