Subject: Re: [v3 PATCH 2/2] powerpc/mm: Dump hash table

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Fri, 18 Nov 2016 11:31:04 +0530

Rashmica Gupta <[email-masked]> writes:

> Useful to be able to dump the kernel hash page table to check
> which pages are hashed along with their sizes and other details.
>
> Add a debugfs file to check the hash page table. If radix is enabled
> (and so there is no hash page table) then this file doesn't exist. To
> use this the PPC_PTDUMP config option must be selected.
>
> Signed-off-by: Rashmica Gupta <[email-masked]>

I completely missed this when it was sent to the list.

> ---
> v2 -> v3: Changed to be compatible with P9.
>
>  arch/powerpc/mm/Makefile             |   3 +-
>  arch/powerpc/mm/dump_hashpagetable.c | 543 +++++++++++++++++++++++++++++++++++
>  2 files changed, 545 insertions(+), 1 deletion(-)
>  create mode 100644 arch/powerpc/mm/dump_hashpagetable.c
>
> diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
> index d3dfa02082b1..df4fbf56aa7b 100644
> --- a/arch/powerpc/mm/Makefile
> +++ b/arch/powerpc/mm/Makefile
> @@ -43,4 +43,5 @@ obj-$(CONFIG_NOT_COHERENT_CACHE) += dma-noncoherent.o
>  obj-$(CONFIG_HIGHMEM)		+= highmem.o
>  obj-$(CONFIG_PPC_COPRO_BASE)	+= copro_fault.o
>  obj-$(CONFIG_SPAPR_TCE_IOMMU)	+= mmu_context_iommu.o
> -obj-$(CONFIG_PPC_PTDUMP)	+= dump_linuxpagetables.o
> +obj-$(CONFIG_PPC_PTDUMP)	+= dump_linuxpagetables.o \
> +				   dump_hashpagetable.o
> diff --git a/arch/powerpc/mm/dump_hashpagetable.c b/arch/powerpc/mm/dump_hashpagetable.c
> new file mode 100644
> index 000000000000..f8ccc224eb2c
> --- /dev/null
> +++ b/arch/powerpc/mm/dump_hashpagetable.c
> @@ -0,0 +1,543 @@
> +/*
> + * Copyright 2016, Rashmica Gupta, IBM Corp.
> + *
> + * This traverses the kernel virtual memory and dumps the pages that are in
> + * the hash pagetable, along with their flags to
> + * /sys/kernel/debug/kernel_hash_pagetable.
> + *
> + * If radix is enabled then there is no hash page table and so no debugfs file
> + * is generated.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; version 2
> + * of the License.
> + */
> +#include <linux/debugfs.h>
> +#include <linux/fs.h>
> +#include <linux/io.h>
> +#include <linux/mm.h>
> +#include <linux/sched.h>
> +#include <linux/seq_file.h>
> +#include <asm/fixmap.h>
> +#include <asm/pgtable.h>
> +#include <linux/const.h>
> +#include <asm/page.h>
> +#include <asm/pgalloc.h>
> +#include <asm/plpar_wrappers.h>
> +#include <linux/memblock.h>
> +#include <asm/firmware.h>
> +
> +struct pg_state {
> +	struct seq_file *seq;
> +	const struct addr_marker *marker;
> +	unsigned long start_address;
> +	unsigned int level;
> +	u64 current_flags;
> +};
> +
> +struct addr_marker {
> +	unsigned long start_address;
> +	const char *name;
> +};
> +
> +static struct addr_marker address_markers[] = {
> +	{ 0,	"Start of kernel VM" },
> +	{ 0,	"vmalloc() Area" },
> +	{ 0,	"vmalloc() End" },
> +	{ 0,	"isa I/O start" },
> +	{ 0,	"isa I/O end" },
> +	{ 0,	"phb I/O start" },
> +	{ 0,	"phb I/O end" },
> +	{ 0,	"I/O remap start" },
> +	{ 0,	"I/O remap end" },
> +	{ 0,	"vmemmap start" },
> +	{ -1,	NULL },
> +};
> +
> +struct flag_info {
> +	u64		mask;
> +	u64		val;
> +	const char	*set;
> +	const char	*clear;
> +	bool		is_val;
> +	int		shift;
> +};
> +
> +static const struct flag_info v_flag_array[] = {
> +	{
> +		.mask   = SLB_VSID_B,
> +		.val    = SLB_VSID_B_256M,
> +		.set    = "ssize: 256M",
> +		.clear  = "ssize: 1T  ",
> +	}, {
> +		.mask	= HPTE_V_SECONDARY,
> +		.val	= HPTE_V_SECONDARY,
> +		.set	= "secondary",
> +		.clear	= "primary  ",
> +	}, {
> +		.mask	= HPTE_V_VALID,
> +		.val	= HPTE_V_VALID,
> +		.set	= "valid  ",
> +		.clear	= "invalid",
> +	}, {
> +		.mask	= HPTE_V_BOLTED,
> +		.val	= HPTE_V_BOLTED,
> +		.set	= "bolted",
> +		.clear	= "",
> +	}
> +};
> +
> +static const struct flag_info r_flag_array[] = {
> +	{
> +		.mask	= HPTE_R_PP0 | HPTE_R_PP,
> +		.val	= PP_RWXX,
> +		.set	= "prot:RW--",
> +	}, {
> +		.mask	= HPTE_R_PP0 | HPTE_R_PP,
> +		.val	= PP_RWRX,
> +		.set	= "prot:RWR-",
> +	}, {
> +		.mask	= HPTE_R_PP0 | HPTE_R_PP,
> +		.val	= PP_RWRW,
> +		.set	= "prot:RWRW",
> +	}, {
> +		.mask	= HPTE_R_PP0 | HPTE_R_PP,
> +		.val	= PP_RXRX,
> +		.set	= "prot:R-R-",
> +	}, {
> +		.mask	= HPTE_R_PP0 | HPTE_R_PP,
> +		.val	= PP_RXXX,
> +		.set	= "prot:R---",
> +	}, {
> +		.mask	= HPTE_R_KEY_HI | HPTE_R_KEY_LO,
> +		.val	= HPTE_R_KEY_HI | HPTE_R_KEY_LO,
> +		.set	= "key",
> +		.clear	= "",
> +		.is_val = true,
> +	}, {
> +		.mask	= HPTE_R_R,
> +		.val	= HPTE_R_R,
> +		.set	= "ref",
> +		.clear	= "   ",
> +	}, {
> +		.mask	= HPTE_R_C,
> +		.val	= HPTE_R_C,
> +		.set	= "changed",
> +		.clear	= "       ",
> +	}, {
> +		.mask	= HPTE_R_N,
> +		.val	= HPTE_R_N,
> +		.set	= "no execute",
> +	}, {
> +		.mask	= HPTE_R_WIMG,
> +		.val	= HPTE_R_W,
> +		.set	= "writethru",
> +	}, {
> +		.mask	= HPTE_R_WIMG,
> +		.val	= HPTE_R_I,
> +		.set	= "no cache",
> +	}, {
> +		.mask	= HPTE_R_WIMG,
> +		.val	= HPTE_R_G,
> +		.set	= "guarded",
> +	}
> +};
> +
> +static int calculate_pagesize(struct pg_state *st, int ps, char s[])
> +{
> +	static const char units[] = "BKMGTPE";
> +	const char *unit = units;
> +
> +	while (ps > 9 && unit[1]) {
> +		ps -= 10;
> +		unit++;
> +	}
> +	seq_printf(st->seq, "  %s_ps: %i%c\t", s, 1<<ps, *unit);
> +	return ps;
> +}
> +
> +static void dump_flag_info(struct pg_state *st, const struct flag_info
> +		*flag, u64 pte, int num)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < num; i++, flag++) {
> +		const char *s = NULL;
> +		u64 val;
> +
> +		/* flag not defined so don't check it */
> +		if (flag->mask == 0)
> +			continue;
> +		/* Some 'flags' are actually values */
> +		if (flag->is_val) {
> +			val = pte & flag->val;
> +			if (flag->shift)
> +				val = val >> flag->shift;
> +			seq_printf(st->seq, "  %s:%llx", flag->set, val);
> +		} else {
> +			if ((pte & flag->mask) == flag->val)
> +				s = flag->set;
> +			else
> +				s = flag->clear;
> +			if (s)
> +				seq_printf(st->seq, "  %s", s);
> +		}
> +	}
> +}
> +
> +static void dump_hpte_info(struct pg_state *st, unsigned long ea, u64 v, u64 r,
> +		unsigned long rpn, int bps, int aps, unsigned long lp)
> +{
> +	int aps_index;
> +
> +	while (ea >= st->marker[1].start_address) {
> +		st->marker++;
> +		seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> +	}
> +	seq_printf(st->seq, "0x%lx:\t", ea);
> +	seq_printf(st->seq, "AVPN:%llx\t", HPTE_V_AVPN_VAL(v));
> +	dump_flag_info(st, v_flag_array, v, ARRAY_SIZE(v_flag_array));
> +	seq_printf(st->seq, "  rpn: %lx\t", rpn);
> +	dump_flag_info(st, r_flag_array, r, ARRAY_SIZE(r_flag_array));
> +
> +	calculate_pagesize(st, bps, "base");
> +	aps_index = calculate_pagesize(st, aps, "actual");
> +	if (aps_index != 2)
> +		seq_printf(st->seq, "LP enc: %lx", lp);
> +	seq_puts(st->seq, "\n");
> +}
> +
> +
> +static int native_find(unsigned long ea, int psize, bool primary, u64 *v, u64
> +		*r)
> +{
> +	struct hash_pte *hptep;
> +	unsigned long hash, vsid, vpn, hpte_group, want_v, hpte_v;
> +	int i, ssize = mmu_kernel_ssize;
> +	unsigned long shift = mmu_psize_defs[psize].shift;
> +
> +	/* calculate hash */
> +	vsid = get_kernel_vsid(ea, ssize);
> +	vpn  = hpt_vpn(ea, vsid, ssize);
> +	hash = hpt_hash(vpn, shift, ssize);
> +	want_v = hpte_encode_avpn(vpn, psize, ssize);
> +
> +	/* to check in the secondary hash table, we invert the hash */
> +	if (!primary)
> +		hash = ~hash;
> +	hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;
> +	for (i = 0; i < HPTES_PER_GROUP; i++) {
> +		hptep = htab_address + hpte_group;
> +		hpte_v = be64_to_cpu(hptep->v);
> +
> +		if (HPTE_V_COMPARE(hpte_v, want_v) && (hpte_v & HPTE_V_VALID)) {
> +			/* HPTE matches */
> +			*v = be64_to_cpu(hptep->v);
> +			*r = be64_to_cpu(hptep->r);
> +			return 0;
> +		}
> +		++hpte_group;
> +	}
> +	return -1;
> +}
> +
> +static int pseries_find(unsigned long ea, int psize, bool primary, u64 *v, u64
> +		*r)
> +{
> +	struct hash_pte ptes[4];
> +	unsigned long vsid, vpn, hash, hpte_group, want_v;
> +	int i, j, ssize = mmu_kernel_ssize;
> +	long lpar_rc = 0;
> +	unsigned long shift = mmu_psize_defs[psize].shift;
> +
> +	/* calculate hash */
> +	vsid = get_kernel_vsid(ea, ssize);
> +	vpn  = hpt_vpn(ea, vsid, ssize);
> +	hash = hpt_hash(vpn, shift, ssize);
> +	want_v = hpte_encode_avpn(vpn, psize, ssize);
> +
> +	/* to check in the secondary hash table, we invert the hash */
> +	if (!primary)
> +		hash = ~hash;
> +	hpte_group = ((hash & htab_hash_mask) * HPTES_PER_GROUP) & ~0x7UL;
> +	/* see if we can find an entry in the hpte with this hash */
> +	for (i = 0; i < HPTES_PER_GROUP; i += 4, hpte_group += 4) {
> +		lpar_rc = plpar_pte_read_4(0, hpte_group, (void *)ptes);
> +
> +		if (lpar_rc != H_SUCCESS)
> +			continue;
> +		for (j = 0; j < 4; j++) {
> +			if (HPTE_V_COMPARE(ptes[j].v, want_v) &&
> +					(ptes[j].v & HPTE_V_VALID)) {
> +				/* HPTE matches */
> +				*v = ptes[j].v;
> +				*r = ptes[j].r;
> +				return 0;
> +			}
> +		}
> +	}
> +	return -1;
> +}
> +
> +static void decode_r(int bps, unsigned long r, unsigned long *rpn, int *aps,
> +		unsigned long *lp_bits)
> +{
> +	struct mmu_psize_def entry;
> +	unsigned long arpn, mask, lp;
> +	int penc = -2, idx = 0, shift;
> +
> +	/*.
> +	 * The LP field has 8 bits. Depending on the actual page size, some of
> +	 * these bits are concatenated with the APRN to get the RPN. The rest
> +	 * of the bits in the LP field is the LP value and is an encoding for
> +	 * the base page size and the actual page size.
> +	 *
> +	 *  -	find the mmu entry for our base page size
> +	 *  -	go through all page encodings and use the associated mask to
> +	 *	find an encoding that matches our encoding in the LP field.
> +	 */
> +	arpn = (r & HPTE_R_RPN) >> HPTE_R_RPN_SHIFT;
> +	lp = arpn & 0xff;
> +
> +	entry = mmu_psize_defs[bps];
> +	while (idx < MMU_PAGE_COUNT) {
> +		penc = entry.penc[idx];
> +		if ((penc != -1) && (mmu_psize_defs[idx].shift)) {
> +			shift = mmu_psize_defs[idx].shift -  HPTE_R_RPN_SHIFT;
> +			mask = (0x1 << (shift)) - 1;
> +			if ((lp & mask) == penc) {
> +				*aps = mmu_psize_to_shift(idx);
> +				*lp_bits = lp & mask;
> +				*rpn = arpn >> shift;
> +				return;
> +			}
> +		}
> +		idx++;
> +	}
> +}
> +
> +static unsigned long hpte_find(struct pg_state *st, unsigned long ea, int psize)
> +{
> +	unsigned long slot;
> +	u64 v  = 0, r = 0;
> +	unsigned long rpn, lp_bits;
> +	int base_psize = 0, actual_psize = 0;
> +
> +	if (ea <= PAGE_OFFSET)
> +		return -1;
> +
> +	/* Look in primary table */
> +	if (firmware_has_feature(FW_FEATURE_LPAR))
> +		slot = pseries_find(ea, psize, true, &v, &r);
> +	else
> +		slot = native_find(ea, psize, true, &v, &r);
> +
> +	/* Look in secondary table */
> +	if (slot == -1) {
> +		if (firmware_has_feature(FW_FEATURE_LPAR))
> +			slot = pseries_find(ea, psize, false, &v, &r);
> +		else
> +			slot = native_find(ea, psize, false, &v, &r);
> +	}
> +
> +	/* No entry found */
> +	if (slot == -1)
> +		return -1;
> +
> +	/* We found an entry in the hash page table:
> +	 *  - check that this has the same base page
> +	 *  - find the actual page size
> +	 *  - find the RPN
> +	 */
> +	base_psize = mmu_psize_to_shift(psize);
> +
> +	if ((v & HPTE_V_LARGE) == HPTE_V_LARGE) {
> +		decode_r(psize, r, &rpn, &actual_psize, &lp_bits);
> +	} else {
> +		/* 4K actual page size */
> +		actual_psize = 12;
> +		rpn = (r & HPTE_R_RPN) >> HPTE_R_RPN_SHIFT;
> +		/* In this case there are no LP bits */
> +		lp_bits = -1;
> +	}
> +	/* We didn't find a matching encoding, so the PTE we found isn't for
> +	 * this address.
> +	 */
> +	if (actual_psize == -1)
> +		return -1;
> +
> +	dump_hpte_info(st, ea, v, r, rpn, base_psize, actual_psize, lp_bits);
> +	return 0;
> +}
> +
> +static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)
> +{
> +	pte_t *pte = pte_offset_kernel(pmd, 0);
> +	unsigned long addr, pteval, psize;
> +	int i, status;
> +
> +	for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
> +		addr = start + i * PAGE_SIZE;
> +		pteval = pte_val(*pte);
> +
> +		if (addr < VMALLOC_END)
> +			psize = mmu_vmalloc_psize;
> +		else
> +			psize = mmu_io_psize;
> +#ifdef CONFIG_PPC_64K_PAGES
> +		/* check for secret 4K mappings */
> +		if (((pteval & H_PAGE_COMBO) == H_PAGE_COMBO) ||
> +			((pteval & H_PAGE_4K_PFN) == H_PAGE_4K_PFN))
> +			psize = mmu_io_psize;
> +#endif
> +		/* check for hashpte */
> +		status = hpte_find(st, addr, psize);
> +
> +		if (((pteval & H_PAGE_HASHPTE) != H_PAGE_HASHPTE)
> +				&& (status != -1)) {
> +		/* found a hpte that is not in the linux page tables */
> +			seq_printf(st->seq, "page probably bolted before linux"
> +				" pagetables were set: addr:%lx, pteval:%lx\n",
> +				addr, pteval);
> +		}
> +	}
> +}
> +
> +static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)
> +{
> +	pmd_t *pmd = pmd_offset(pud, 0);
> +	unsigned long addr;
> +	unsigned int i;
> +
> +	for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
> +		addr = start + i * PMD_SIZE;
> +		if (!pmd_none(*pmd))
> +			/* pmd exists */
> +			walk_pte(st, pmd, addr);

Is that correct ? we need to handle bad_pmd, hugetlb entries, THP
entries etc right ? Also while walking we also need to make sure it is
not getting split. 

> +	}
> +}
> +
> +static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
> +{
> +	pud_t *pud = pud_offset(pgd, 0);
> +	unsigned long addr;
> +	unsigned int i;
> +
> +	for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
> +		addr = start + i * PUD_SIZE;
> +		if (!pud_none(*pud))
> +			/* pud exists */
> +			walk_pmd(st, pud, addr);
> +	}
> +}
> +
> +static void walk_pagetables(struct pg_state *st)
> +{
> +	pgd_t *pgd = pgd_offset_k(0UL);
> +	unsigned int i;
> +	unsigned long addr;
> +
> +	/*
> +	 * Traverse the linux pagetable structure and dump pages that are in
> +	 * the hash pagetable.
> +	 */
> +	for (i = 0; i < PTRS_PER_PGD; i++, pgd++) {
> +		addr = KERN_VIRT_START + i * PGDIR_SIZE;
> +		if (!pgd_none(*pgd))
> +			/* pgd exists */
> +			walk_pud(st, pgd, addr);
> +	}
> +}
> +
> +
> +static void walk_linearmapping(struct pg_state *st)
> +{
> +	unsigned long addr;
> +
> +	/*
> +	 * Traverse the linear mapping section of virtual memory and dump pages
> +	 * that are in the hash pagetable.
> +	 */
> +	unsigned long psize = 1 << mmu_psize_defs[mmu_linear_psize].shift;
> +
> +	for (addr = PAGE_OFFSET; addr < PAGE_OFFSET +
> +			memblock_phys_mem_size(); addr += psize)
> +		hpte_find(st, addr, mmu_linear_psize);
> +}
> +
> +static void walk_vmemmap(struct pg_state *st)
> +{
> +	struct vmemmap_backing *ptr = vmemmap_list;
> +
> +	/*
> +	 * Traverse the vmemmaped memory and dump pages that are in the hash
> +	 * pagetable.
> +	 */
> +	while (ptr->list) {
> +		hpte_find(st, ptr->virt_addr, mmu_vmemmap_psize);
> +		ptr = ptr->list;
> +	}
> +	seq_puts(st->seq, "---[ vmemmap end ]---\n");
> +}
> +
> +static void populate_markers(void)
> +{
> +	address_markers[0].start_address = PAGE_OFFSET;
> +	address_markers[1].start_address = VMALLOC_START;
> +	address_markers[2].start_address = VMALLOC_END;
> +	address_markers[3].start_address = ISA_IO_BASE;
> +	address_markers[4].start_address = ISA_IO_END;
> +	address_markers[5].start_address = PHB_IO_BASE;
> +	address_markers[6].start_address = PHB_IO_END;
> +	address_markers[7].start_address = IOREMAP_BASE;
> +	address_markers[8].start_address = IOREMAP_END;
> +#ifdef CONFIG_PPC_STD_MMU_64
> +	address_markers[9].start_address =  H_VMEMMAP_BASE;
> +#else
> +	address_markers[9].start_address =  VMEMMAP_BASE;
> +#endif
> +}
> +
> +static int ptdump_show(struct seq_file *m, void *v)
> +{
> +	struct pg_state st = {
> +		.seq = m,
> +		.start_address = PAGE_OFFSET,
> +		.marker = address_markers,
> +	};
> +	/*
> +	 * Traverse the 0xc, 0xd and 0xf areas of the kernel virtual memory and
> +	 * dump pages that are in the hash pagetable.
> +	 */
> +	walk_linearmapping(&st);
> +	walk_pagetables(&st);
> +	walk_vmemmap(&st);
> +	return 0;
> +}
> +
> +static int ptdump_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, ptdump_show, NULL);
> +}
> +
> +static const struct file_operations ptdump_fops = {
> +	.open		= ptdump_open,
> +	.read		= seq_read,
> +	.llseek		= seq_lseek,
> +	.release	= single_release,
> +};
> +
> +static int ptdump_init(void)
> +{
> +	struct dentry *debugfs_file;
> +
> +	if (!radix_enabled()) {
> +		populate_markers();
> +		debugfs_file = debugfs_create_file("kernel_hash_pagetable",
> +				0400, NULL, NULL, &ptdump_fops);
> +		return debugfs_file ? 0 : -ENOMEM;
> +	}
> +	return 0;
> +}
> +device_initcall(ptdump_init);
> -- 
> 2.5.0
>
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