[PATCH v0] ARMv8:mm:Support the DEBUG_PAGEALLOC
zhichang.yuan
zhichang.yuan at linaro.org
Mon Oct 27 23:11:22 PDT 2014
Hi, Laura,
Thanks for your comments!
On 2014年10月28日 06:25, Laura Abbott wrote:
> Hi,
>
> On 10/26/2014 9:01 PM, zhichang.yuan at linaro.org wrote:
>> From: "zhichang.yuan" <zhichang.yuan at linaro.org>
>>
>> This patch targets to support DEBUG_PAGEALLOC on ARMv8.
>>
>> Meanwhile, it adds the processing to free some unused
>> page tables created in direct kernel mapping.
>>
>
> It might be good to split out the freeing of the page
> tables into a separate patch for review since it looks to be
> separate of DEBUG_PAGEALLOC.
>
Yes. It is not relative to DEBUG_PAGEALLOC.
I just think it is small change, so do not break down it.
But it is not right.
I will separate it.
>> The patch was tested based on the following code @:
>> https://git.linaro.org/people/zhichang.yuan/pgalloc.git/shortlog/refs/heads/test_pgalloc_v1
>>
>> Signed-off-by: Zhichang Yuan <zhichang.yuan at linaro.org>
>> ---
>> arch/arm64/Kconfig | 3 +
>> arch/arm64/include/asm/pgtable-hwdef.h | 6 +
>> arch/arm64/include/asm/pgtable.h | 21 +++
>> arch/arm64/mm/mmu.c | 263 +++++++++++++++++++++++++++++++-
>> 4 files changed, 288 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index fd4e81a..da072d4 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -128,6 +128,9 @@ config KERNEL_MODE_NEON
>> config FIX_EARLYCON_MEM
>> def_bool y
>>
>> +config ARCH_SUPPORTS_DEBUG_PAGEALLOC
>> + def_bool y
>> +
>> source "init/Kconfig"
>>
>> source "kernel/Kconfig.freezer"
>> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
>> index 88174e0..0a62e9a 100644
>> --- a/arch/arm64/include/asm/pgtable-hwdef.h
>> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
>> @@ -65,6 +65,12 @@
>> #define PUD_TYPE_SECT (_AT(pgdval_t, 1) << 0)
>>
>> /*
>> + * Section
>> + */
>> +#define PUD_SECT_VALID (_AT(pmdval_t, 1) << 0)
>> +#define PUD_SECT_PROT_NONE (_AT(pmdval_t, 1) << 58)
>> +
>> +/*
>> * Level 2 descriptor (PMD).
>> */
>> #define PMD_TYPE_MASK (_AT(pmdval_t, 3) << 0)
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index ffe1ba0..4246f3b 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -313,9 +313,12 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>>
>> #ifdef CONFIG_ARM64_64K_PAGES
>> #define pud_sect(pud) (0)
>> +#define pud_table(pud) (1)
>> #else
>> #define pud_sect(pud) ((pud_val(pud) & PUD_TYPE_MASK) == \
>> PUD_TYPE_SECT)
>> +#define pud_table(pud) ((pud_val(pud) & PUD_TYPE_MASK) == \
>> + PUD_TYPE_TABLE)
>> #endif
>>
>> static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
>> @@ -422,6 +425,14 @@ static inline pud_t *pud_offset(pgd_t *pgd, unsigned long addr)
>> /* to find an entry in a kernel page-table-directory */
>> #define pgd_offset_k(addr) pgd_offset(&init_mm, addr)
>>
>> +
>> +#define PHYSICAL_PAGE_MASK (((signed long)PAGE_MASK) & PHYS_MASK)
>> +/* PTE_PFN_MASK extracts the PFN from a (pte|pmd|pud|pgd)val_t */
>> +#define PTE_PFN_MASK ((pteval_t)PHYSICAL_PAGE_MASK)
>> +
>> +/* PTE_FLAGS_MASK extracts the flags from a (pte|pmd|pud|pgd)val_t */
>> +#define PTE_FLAGS_MASK (~PTE_PFN_MASK)
>> +
>> static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
>> {
>> const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY |
>> @@ -477,6 +488,16 @@ extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
>>
>> #define PTE_FILE_MAX_BITS 55
>>
>> +extern pte_t *lookup_kaddress(unsigned long address, unsigned int *level);
>> +
>> +enum pg_level {
>> + PG_LEVEL_NONE,
>> + PG_LEVEL_PAGE,
>> + PG_LEVEL_PMD,
>> + PG_LEVEL_PUD,
>> + PG_LEVEL_NUM
>> +};
>> +
>> extern int kern_addr_valid(unsigned long addr);
>>
>> #include <asm-generic/pgtable.h>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index c555672..6bc5f70 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -132,10 +132,21 @@ EXPORT_SYMBOL(phys_mem_access_prot);
>> static void __init *early_alloc(unsigned long sz)
>> {
>> void *ptr = __va(memblock_alloc(sz, sz));
>> +
>> memset(ptr, 0, sz);
>> return ptr;
>> }
>>
>> +/*Free the page used as pmd table entry in direct mapping*/
>> +static inline void __init pmd_table_free(pmd_t *pmd, unsigned long addr)
>> +{
>> + if (pmd_table(*pmd)) {
>> + phys_addr_t table = __pa(pte_offset_kernel(pmd, 0));
>> +
>
> pte_offset_kernel -> pmd_page_vaddr which calls __va already. Is
> there another way to get the physical address without having to go
> pa -> va -> pa again?
>
Yes. It seems to be verbose when offset is 0. I want to use existed macro.
I think i had other two options.
First, directly get the physical address just like that:
pmd_val(*pmd) & PHYS_MASK & (s32)PAGE_MASK
or
pte_pfn(pmd_pte(*pmd)) << PAGE_SHIFT
Maybe the front one is better.
>> + memblock_free(table, PAGE_SIZE);
>> + }
>> +}
>> +
>> static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
>> unsigned long end, unsigned long pfn,
>> pgprot_t prot)
>> @@ -185,14 +196,16 @@ static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,
>> next = pmd_addr_end(addr, end);
>> /* try section mapping first */
>> if (((addr | next | phys) & ~SECTION_MASK) == 0) {
>> - pmd_t old_pmd =*pmd;
>> + pmd_t old_pmd = *pmd;
>> +
>> set_pmd(pmd, __pmd(phys | prot_sect));
>> /*
>> * Check for previous table entries created during
>> * boot (__create_page_tables) and flush them.
>> */
>> if (!pmd_none(old_pmd))
>> - flush_tlb_all();
>> + flush_tlb_kernel_range(addr, next);
> Was the switch from flush_tlb_all -> flush_tlb_kernel_range found from
> code inspection or as part of something else? Do you have any performance
> data about from this switch?
>
As for this issue, i have no performance data. But you can check the implementation of flush_tlb_kernel_range.
when the pages size to be flushed is over MAX_TLB_RANGE, it will call __flush_tlb_kernel_range; otherwise, same as
flush_tlb_all. I think someone had evaluated the performance difference.
>> + pmd_table_free(&old_pmd, addr);
>> } else {
>> alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
>> prot_pte);
>> @@ -224,6 +237,7 @@ static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
>> if (!map_io && (PAGE_SHIFT == 12) &&
>> ((addr | next | phys) & ~PUD_MASK) == 0) {
>> pud_t old_pud = *pud;
>> +
>> set_pud(pud, __pud(phys | PROT_SECT_NORMAL_EXEC));
>>
>> /*
>> @@ -234,9 +248,15 @@ static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
>> * Look up the old pmd table and free it.
>> */
>> if (!pud_none(old_pud)) {
>> - phys_addr_t table = __pa(pmd_offset(&old_pud, 0));
>> - memblock_free(table, PAGE_SIZE);
>> - flush_tlb_all();
>> + flush_tlb_kernel_range(addr, next);
>> + if (pud_table(old_pud)) {
>> + phys_addr_t table =
>> + __pa(pmd_offset(&old_pud, 0));
>> + pmd_t *pmd = pmd_offset(pud, addr);
>> +
>> + pmd_table_free(pmd, addr);
>> + memblock_free(table, PAGE_SIZE);
>> + }
>> }
>> } else {
>> alloc_init_pmd(pud, addr, next, phys, map_io);
>> @@ -287,6 +307,219 @@ void __init create_id_mapping(phys_addr_t addr, phys_addr_t size, int map_io)
>> addr, addr, size, map_io);
>> }
>>
>> +static inline pte_t *lookup_kaddress_in_pgd(pgd_t *pgd,
>> + unsigned long address,
>> + unsigned int *level)
>> +{
>> + pud_t *pud;
>> + pmd_t *pmd;
>> +
>> + *level = PG_LEVEL_NONE;
>> +
>> + if (pgd_none(*pgd))
>> + return NULL;
>> +
>> + pud = pud_offset(pgd, address);
>> + if (pud_none(*pud))
>> + return NULL;
>> +
>> + *level = PG_LEVEL_PUD;
>> + if (pud_sect(*pud) || !(pud_val(*pud) & PUD_SECT_VALID))
>> + return (pte_t *)pud;
>> +
>> + pmd = pmd_offset(pud, address);
>> + if (pmd_none(*pmd))
>> + return NULL;
>> +
>> + /*
>> + * !(pmd_val(*pmd) & PMD_SECT_VALID) means PMD_TYPE_MASK &(*pmd)
>> + * is 0, but *pmd is non-zero.
>> + * For Huge page split.
>> + */
>> + *level = PG_LEVEL_PMD;
>> + if (pmd_sect(*pmd) || !(pmd_val(*pmd) & PMD_SECT_VALID))
>> + return (pte_t *)pmd;
>> +
>> + *level = PG_LEVEL_PAGE;
>> +
>> + return pte_offset_kernel(pmd, address);
>> +}
>> +
>> +
>> +pte_t *lookup_kaddress(unsigned long address, unsigned int *level)
>> +{
>> + return lookup_kaddress_in_pgd(pgd_offset_k(address), address, level);
>> +}
>> +EXPORT_SYMBOL_GPL(lookup_kaddress);
>
> Do you need the EXPORT_SYMBOL right now?
Because my original test code is module, and call this function.
>
>> +
>> +
>> +#ifdef CONFIG_DEBUG_PAGEALLOC
>> +
>> +static void __split_pmd_page_mapping(pmd_t *pmd,
>> + unsigned long addr,
>> + void *p_base)
>> +{
>> + pte_t *pte_base;
>> + int i;
>> +
>> + pgprot_t prot_val;
>> +
>> + unsigned long pfn;
>> +
>> + pte_base = (pte_t *)p_base;
>> +
>> + /*get the original pgprot value.*/
>> + prot_val = pmd_val(*pmd) & PTE_FLAGS_MASK;
>> + prot_val &= ~PTE_TYPE_MASK;
>> + prot_val |= PTE_TYPE_PAGE;
>> +
>> + pfn = pmd_pfn(*pmd);
>> + for (i = 0; i < PTRS_PER_PTE; i++, pfn += 1)
>> + set_pte(pte_base + i, pfn_pte(pfn, prot_val));
>> +
>> + __pmd_populate(pmd, __pa(pte_base), PMD_TYPE_TABLE);
>> + flush_tlb_kernel_range((addr & PMD_MASK),
>> + ((addr + PMD_SIZE) & PMD_MASK));
>> +}
>> +
>> +
>> +static void __split_pud_page_mapping(pud_t *pud,
>> + unsigned long addr,
>> + void *p_base)
>> +{
>> + int i;
>> +
>> + pgprot_t old_prot;
>> +
>> + unsigned long pfn, pfn_inc;
>> +
>> + pmd_t *pmd_base = (pmd_t *)p_base;
>> +
>> + /*get the original pgprot value.*/
>> + old_prot = pud_val(*pud) & PTE_FLAGS_MASK;
>> +
>> + pfn = pud_pfn(*pud);
>> + pfn_inc = PMD_SIZE >> PAGE_SHIFT;
>> + for (i = 0; i < PTRS_PER_PMD; i++, pfn += pfn_inc)
>> + set_pmd(pmd_base + i, pfn_pmd(pfn, old_prot));
>> +
>> + pud_populate(&init_mm, pud, pmd_base);
>> + flush_tlb_all();
>
> Everywhere else you've switched to using flush_tlb_kernel_range,
> why the switch here to flush_tlb_all?
>
Since here process PUD, a larger size.
>> +}
>> +
>> +void kernel_map_pages(struct page *page, int numpages, int enable)
>> +{
>> + unsigned long start_addr, end_addr, addr;
>> + unsigned int level;
>> +
>> + pte_t *kpte;
>> + pteval_t old_pval, new_pval;
>> +
>> + int i, counter = 0;
>> +
>> + /*no highmem in ARMv8. */
>> + addr = start_addr = (unsigned long)page_address(page);
>> + end_addr = start_addr + (numpages << PAGE_SHIFT);
>> +
>> + for (i = 0; i < numpages; addr += PAGE_SIZE, i++) {
>> + kpte = lookup_kaddress(addr, &level);
>> + /*
>> + * skip the memory holes. it is impossible if the input
>> + * parameter is valid.
>> + */
>> + if (unlikely(!kpte || pte_none(*kpte))) {
>> + pr_err("Have no kernel linear mapping for 0x%0lx\n", addr);
>> + break;
>> + }
>> +
>> + if (level != PG_LEVEL_PAGE) {
>> + pr_err("Page entry for 0x%0lx is not PAGE LEVEL(%d)\n",
>> + addr, level);
>> + break;
>> + }
>> +
>> + old_pval = pte_val(*kpte);
>> + new_pval = (enable) ? (old_pval | PTE_VALID) :
>> + (old_pval & (~PTE_VALID));
>> + if (unlikely(new_pval == old_pval)) {
>> + pr_warn("Page %s: same pte value at 0x%llx",
>> + (enable) ? "alloc" : "free", old_pval);
>> + continue;
>> + }
>> +
>> + set_pte(kpte, __pte(new_pval));
>> + counter++;
>> + }
>> +
>> + if (counter)
>> + flush_tlb_kernel_range(start_addr, end_addr);
>> +}
>
> We already have some of this infrastructure to set page attributes
> in arch/arm64/mm/pageattr.c . We should be leveraging that for
> kernel_map_pages.
>
There is no pageattr.c for ARMv8. In X86, it exists.
Do you mean pmd_modify?
>> +
>> +
>> +static int __init early_split_large_page_mapping(unsigned long virt,
>> + phys_addr_t phys,
>> + phys_addr_t size)
>> +{
>> + pte_t *pte;
>> + void *pte_base;
>> +
>> + unsigned long addr, end, next;
>> + unsigned int pg_level;
>> + unsigned long size_level;
>> + unsigned long mask_level;
>> +
>> + /*make the addr aligned to PAGE*/
>> + addr = virt & PAGE_MASK;
>> + end = addr + PAGE_ALIGN(size + (virt & ~PAGE_MASK));
>> +
>> + for (; addr != end; phys += (next - addr), addr = next) {
>> +repeat:
>> + pte = lookup_kaddress(addr, &pg_level);
>> + /*
>> + * support the input memory range is a wider range. If we
>> + * can not find valid page entry for some addresses, we do
>> + * not know the page section size. But we only care the
>> + * large page, just move forward in minimal large page size
>> + * (PMD size)
>> + */
>> + if (!pte || pte_none(*pte)) {
>> + next = pmd_addr_end(addr, end);
>> + continue;
>> + }
>> +
>> + size_level = (_AC(1, UL) <<
>> + ((PAGE_SHIFT - 3) * pg_level + 3));
>> + mask_level = ~(size_level - 1);
>> +
>> + next = (addr + size_level) & mask_level;
>> + if (next > end)
>> + next = end;
>> +
>> + /*Does it need to split it?*/
>> + if (pg_level == PG_LEVEL_PAGE)
>> + continue;
>> +
>> + /*start the splitting...*/
>> + if (pte_pfn(*pte) != PFN_DOWN(phys & mask_level)) {
>> + pr_err("Physical addr 0x%0llx mis-match with virt 0x%0lx\n",
>> + pte_pfn(*pte), addr & mask_level);
>> + return -1;
>
> Return a real error code here and not just -1
>
Yes. Maybe EFAULT is more better.
>> + }
>> +
>> + pte_base = early_alloc(PAGE_SIZE);
>> +
>> + if (pg_level == PG_LEVEL_PUD) {
>> + __split_pud_page_mapping((pud_t *)pte, addr, pte_base);
>> + goto repeat;
>
> This looks like a less friendly use of goto. Any change we could turn this
> into a real loop?
>
I just want to make __split_pud_page_mapping more concise and just for the split from pud to pmd.
Best,
-Zhichang
>> + }
>> + __split_pmd_page_mapping((pmd_t *)pte, addr, pte_base);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +
>> +#endif
>> static void __init map_mem(void)
>> {
>> struct memblock_region *reg;
>> @@ -331,6 +564,26 @@ static void __init map_mem(void)
>> create_mapping(start, __phys_to_virt(start), end - start);
>> }
>>
>> +#ifdef CONFIG_DEBUG_PAGEALLOC
>> + /*
>> + * the biggest direct mapping is ready, then start the PTE building.
>> + * Now,there are sufficient mapped pages to store the PTE tables.
>> + * And more important, doing large page splitting here can dispose
>> + * the page tables in contiguous memory area.
>> + */
>> + for_each_memblock(memory, reg) {
>> + phys_addr_t start = reg->base;
>> + phys_addr_t end = start + reg->size;
>> +
>> + if (start >= end || PFN_UP(start) >= PFN_DOWN(end))
>> + break;
>> +
>> + if (early_split_large_page_mapping(__phys_to_virt(start),
>> + start, end - start))
>> + panic("map_mem:Fail to split large page[0x%0llx,0x%0llx)\n",
>> + start, end);
>> + }
>> +#endif
>> /* Limit no longer required. */
>> memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);
>> }
>>
>
> Thanks,
> Laura
>
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