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Revision fe9a552e715dfe5167d52deb74ea16335896bdaf authored by Dan Williams on 21 March 2018, 22:12:07 UTC, committed by Dan Williams on 21 March 2018, 22:12:07 UTC 
libnvdimm, nfit: fix persistence domain reporting
 
The persistence domain is a point in the platform where once writes
reach that destination the platform claims it will make them persistent
relative to power loss. In the ACPI NFIT this is currently communicated
as 2 bits in the "NFIT - Platform Capabilities Structure". The bits
comprise a hierarchy, i.e. bit0 "CPU Cache Flush to NVDIMM Durability on
Power Loss Capable" implies bit1 "Memory Controller Flush to NVDIMM
Durability on Power Loss Capable".

Commit 96c3a239054a "libnvdimm: expose platform persistence attr..."
shows the persistence domain as flags, but it's really an enumerated
hierarchy.

Fix this newly introduced user ABI to show the closest available
persistence domain before userspace develops dependencies on seeing, or
needing to develop code to tolerate, the raw NFIT flags communicated
through the libnvdimm-generic region attribute.

Fixes: 96c3a239054a ("libnvdimm: expose platform persistence attr...")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
1 parent 896196d
Raw File
page_poison.c 
// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/page_ext.h>
#include <linux/poison.h>
#include <linux/ratelimit.h>

static bool want_page_poisoning __read_mostly;

static int early_page_poison_param(char *buf)
{
	if (!buf)
		return -EINVAL;
	return strtobool(buf, &want_page_poisoning);
}
early_param("page_poison", early_page_poison_param);

bool page_poisoning_enabled(void)
{
	/*
	 * Assumes that debug_pagealloc_enabled is set before
	 * free_all_bootmem.
	 * Page poisoning is debug page alloc for some arches. If
	 * either of those options are enabled, enable poisoning.
	 */
	return (want_page_poisoning ||
		(!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
		debug_pagealloc_enabled()));
}

static void poison_page(struct page *page)
{
	void *addr = kmap_atomic(page);

	memset(addr, PAGE_POISON, PAGE_SIZE);
	kunmap_atomic(addr);
}

static void poison_pages(struct page *page, int n)
{
	int i;

	for (i = 0; i < n; i++)
		poison_page(page + i);
}

static bool single_bit_flip(unsigned char a, unsigned char b)
{
	unsigned char error = a ^ b;

	return error && !(error & (error - 1));
}

static void check_poison_mem(unsigned char *mem, size_t bytes)
{
	static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
	unsigned char *start;
	unsigned char *end;

	if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
		return;

	start = memchr_inv(mem, PAGE_POISON, bytes);
	if (!start)
		return;

	for (end = mem + bytes - 1; end > start; end--) {
		if (*end != PAGE_POISON)
			break;
	}

	if (!__ratelimit(&ratelimit))
		return;
	else if (start == end && single_bit_flip(*start, PAGE_POISON))
		pr_err("pagealloc: single bit error\n");
	else
		pr_err("pagealloc: memory corruption\n");

	print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
			end - start + 1, 1);
	dump_stack();
}

static void unpoison_page(struct page *page)
{
	void *addr;

	addr = kmap_atomic(page);
	/*
	 * Page poisoning when enabled poisons each and every page
	 * that is freed to buddy. Thus no extra check is done to
	 * see if a page was posioned.
	 */
	check_poison_mem(addr, PAGE_SIZE);
	kunmap_atomic(addr);
}

static void unpoison_pages(struct page *page, int n)
{
	int i;

	for (i = 0; i < n; i++)
		unpoison_page(page + i);
}

void kernel_poison_pages(struct page *page, int numpages, int enable)
{
	if (!page_poisoning_enabled())
		return;

	if (enable)
		unpoison_pages(page, numpages);
	else
		poison_pages(page, numpages);
}

#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable)
{
	/* This function does nothing, all work is done via poison pages */
}
#endif
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