Subject: [PATCH v0] ARMv8:mm:Support the DEBUG_PAGEALLOC

From: [email-masked] (Laura Abbott)
Date: Mon, 27 Oct 2014 15:25:34 -0700

Hi,

On 10/26/2014 9:01 PM, zhichang.yuan at linaro.org wrote:
> From: "zhichang.yuan" <[email-masked]>
>
> 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 <[email-masked]>
> ---
>   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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