[PATCH v0] ARMv8:mm:Support the DEBUG_PAGEALLOC
Laura Abbott
lauraa at codeaurora.org
Mon Oct 27 15:25:34 PDT 2014
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.
> 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?
> + 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?
> + 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?
> +
> +
> +#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?
> +}
> +
> +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.
> +
> +
> +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
> + }
> +
> + 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?
> + }
> + __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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