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-rw-r--r--Documentation/vm/hwpoison.txt136
-rw-r--r--Documentation/vm/ksm.txt13
-rw-r--r--Documentation/vm/page-types.c304
-rw-r--r--Documentation/vm/pagemap.txt8
4 files changed, 361 insertions, 100 deletions
diff --git a/Documentation/vm/hwpoison.txt b/Documentation/vm/hwpoison.txt
new file mode 100644
index 00000000000..3ffadf8da61
--- /dev/null
+++ b/Documentation/vm/hwpoison.txt
@@ -0,0 +1,136 @@
+What is hwpoison?
+
+Upcoming Intel CPUs have support for recovering from some memory errors
+(``MCA recovery''). This requires the OS to declare a page "poisoned",
+kill the processes associated with it and avoid using it in the future.
+
+This patchkit implements the necessary infrastructure in the VM.
+
+To quote the overview comment:
+
+ * High level machine check handler. Handles pages reported by the
+ * hardware as being corrupted usually due to a 2bit ECC memory or cache
+ * failure.
+ *
+ * This focusses on pages detected as corrupted in the background.
+ * When the current CPU tries to consume corruption the currently
+ * running process can just be killed directly instead. This implies
+ * that if the error cannot be handled for some reason it's safe to
+ * just ignore it because no corruption has been consumed yet. Instead
+ * when that happens another machine check will happen.
+ *
+ * Handles page cache pages in various states. The tricky part
+ * here is that we can access any page asynchronous to other VM
+ * users, because memory failures could happen anytime and anywhere,
+ * possibly violating some of their assumptions. This is why this code
+ * has to be extremely careful. Generally it tries to use normal locking
+ * rules, as in get the standard locks, even if that means the
+ * error handling takes potentially a long time.
+ *
+ * Some of the operations here are somewhat inefficient and have non
+ * linear algorithmic complexity, because the data structures have not
+ * been optimized for this case. This is in particular the case
+ * for the mapping from a vma to a process. Since this case is expected
+ * to be rare we hope we can get away with this.
+
+The code consists of a the high level handler in mm/memory-failure.c,
+a new page poison bit and various checks in the VM to handle poisoned
+pages.
+
+The main target right now is KVM guests, but it works for all kinds
+of applications. KVM support requires a recent qemu-kvm release.
+
+For the KVM use there was need for a new signal type so that
+KVM can inject the machine check into the guest with the proper
+address. This in theory allows other applications to handle
+memory failures too. The expection is that near all applications
+won't do that, but some very specialized ones might.
+
+---
+
+There are two (actually three) modi memory failure recovery can be in:
+
+vm.memory_failure_recovery sysctl set to zero:
+ All memory failures cause a panic. Do not attempt recovery.
+ (on x86 this can be also affected by the tolerant level of the
+ MCE subsystem)
+
+early kill
+ (can be controlled globally and per process)
+ Send SIGBUS to the application as soon as the error is detected
+ This allows applications who can process memory errors in a gentle
+ way (e.g. drop affected object)
+ This is the mode used by KVM qemu.
+
+late kill
+ Send SIGBUS when the application runs into the corrupted page.
+ This is best for memory error unaware applications and default
+ Note some pages are always handled as late kill.
+
+---
+
+User control:
+
+vm.memory_failure_recovery
+ See sysctl.txt
+
+vm.memory_failure_early_kill
+ Enable early kill mode globally
+
+PR_MCE_KILL
+ Set early/late kill mode/revert to system default
+ arg1: PR_MCE_KILL_CLEAR: Revert to system default
+ arg1: PR_MCE_KILL_SET: arg2 defines thread specific mode
+ PR_MCE_KILL_EARLY: Early kill
+ PR_MCE_KILL_LATE: Late kill
+ PR_MCE_KILL_DEFAULT: Use system global default
+PR_MCE_KILL_GET
+ return current mode
+
+
+---
+
+Testing:
+
+madvise(MADV_POISON, ....)
+ (as root)
+ Poison a page in the process for testing
+
+
+hwpoison-inject module through debugfs
+ /sys/debug/hwpoison/corrupt-pfn
+
+Inject hwpoison fault at PFN echoed into this file
+
+
+Architecture specific MCE injector
+
+x86 has mce-inject, mce-test
+
+Some portable hwpoison test programs in mce-test, see blow.
+
+---
+
+References:
+
+http://halobates.de/mce-lc09-2.pdf
+ Overview presentation from LinuxCon 09
+
+git://git.kernel.org/pub/scm/utils/cpu/mce/mce-test.git
+ Test suite (hwpoison specific portable tests in tsrc)
+
+git://git.kernel.org/pub/scm/utils/cpu/mce/mce-inject.git
+ x86 specific injector
+
+
+---
+
+Limitations:
+
+- Not all page types are supported and never will. Most kernel internal
+objects cannot be recovered, only LRU pages for now.
+- Right now hugepage support is missing.
+
+---
+Andi Kleen, Oct 2009
+
diff --git a/Documentation/vm/ksm.txt b/Documentation/vm/ksm.txt
index 72a22f65960..262d8e6793a 100644
--- a/Documentation/vm/ksm.txt
+++ b/Documentation/vm/ksm.txt
@@ -52,15 +52,15 @@ The KSM daemon is controlled by sysfs files in /sys/kernel/mm/ksm/,
readable by all but writable only by root:
max_kernel_pages - set to maximum number of kernel pages that KSM may use
- e.g. "echo 2000 > /sys/kernel/mm/ksm/max_kernel_pages"
+ e.g. "echo 100000 > /sys/kernel/mm/ksm/max_kernel_pages"
Value 0 imposes no limit on the kernel pages KSM may use;
but note that any process using MADV_MERGEABLE can cause
KSM to allocate these pages, unswappable until it exits.
- Default: 2000 (chosen for demonstration purposes)
+ Default: quarter of memory (chosen to not pin too much)
pages_to_scan - how many present pages to scan before ksmd goes to sleep
- e.g. "echo 200 > /sys/kernel/mm/ksm/pages_to_scan"
- Default: 200 (chosen for demonstration purposes)
+ e.g. "echo 100 > /sys/kernel/mm/ksm/pages_to_scan"
+ Default: 100 (chosen for demonstration purposes)
sleep_millisecs - how many milliseconds ksmd should sleep before next scan
e.g. "echo 20 > /sys/kernel/mm/ksm/sleep_millisecs"
@@ -70,7 +70,8 @@ run - set 0 to stop ksmd from running but keep merged pages,
set 1 to run ksmd e.g. "echo 1 > /sys/kernel/mm/ksm/run",
set 2 to stop ksmd and unmerge all pages currently merged,
but leave mergeable areas registered for next run
- Default: 1 (for immediate use by apps which register)
+ Default: 0 (must be changed to 1 to activate KSM,
+ except if CONFIG_SYSFS is disabled)
The effectiveness of KSM and MADV_MERGEABLE is shown in /sys/kernel/mm/ksm/:
@@ -86,4 +87,4 @@ pages_volatile embraces several different kinds of activity, but a high
proportion there would also indicate poor use of madvise MADV_MERGEABLE.
Izik Eidus,
-Hugh Dickins, 30 July 2009
+Hugh Dickins, 24 Sept 2009
diff --git a/Documentation/vm/page-types.c b/Documentation/vm/page-types.c
index fa1a30d9e9d..4793c6aac73 100644
--- a/Documentation/vm/page-types.c
+++ b/Documentation/vm/page-types.c
@@ -2,7 +2,10 @@
* page-types: Tool for querying page flags
*
* Copyright (C) 2009 Intel corporation
- * Copyright (C) 2009 Wu Fengguang <fengguang.wu@intel.com>
+ *
+ * Authors: Wu Fengguang <fengguang.wu@intel.com>
+ *
+ * Released under the General Public License (GPL).
*/
#define _LARGEFILE64_SOURCE
@@ -69,7 +72,9 @@
#define KPF_COMPOUND_TAIL 16
#define KPF_HUGE 17
#define KPF_UNEVICTABLE 18
+#define KPF_HWPOISON 19
#define KPF_NOPAGE 20
+#define KPF_KSM 21
/* [32-] kernel hacking assistances */
#define KPF_RESERVED 32
@@ -116,7 +121,9 @@ static char *page_flag_names[] = {
[KPF_COMPOUND_TAIL] = "T:compound_tail",
[KPF_HUGE] = "G:huge",
[KPF_UNEVICTABLE] = "u:unevictable",
+ [KPF_HWPOISON] = "X:hwpoison",
[KPF_NOPAGE] = "n:nopage",
+ [KPF_KSM] = "x:ksm",
[KPF_RESERVED] = "r:reserved",
[KPF_MLOCKED] = "m:mlocked",
@@ -152,9 +159,6 @@ static unsigned long opt_size[MAX_ADDR_RANGES];
static int nr_vmas;
static unsigned long pg_start[MAX_VMAS];
static unsigned long pg_end[MAX_VMAS];
-static unsigned long voffset;
-
-static int pagemap_fd;
#define MAX_BIT_FILTERS 64
static int nr_bit_filters;
@@ -163,9 +167,16 @@ static uint64_t opt_bits[MAX_BIT_FILTERS];
static int page_size;
-#define PAGES_BATCH (64 << 10) /* 64k pages */
+static int pagemap_fd;
static int kpageflags_fd;
+static int opt_hwpoison;
+static int opt_unpoison;
+
+static char *hwpoison_debug_fs = "/debug/hwpoison";
+static int hwpoison_inject_fd;
+static int hwpoison_forget_fd;
+
#define HASH_SHIFT 13
#define HASH_SIZE (1 << HASH_SHIFT)
#define HASH_MASK (HASH_SIZE - 1)
@@ -207,6 +218,74 @@ static void fatal(const char *x, ...)
exit(EXIT_FAILURE);
}
+static int checked_open(const char *pathname, int flags)
+{
+ int fd = open(pathname, flags);
+
+ if (fd < 0) {
+ perror(pathname);
+ exit(EXIT_FAILURE);
+ }
+
+ return fd;
+}
+
+/*
+ * pagemap/kpageflags routines
+ */
+
+static unsigned long do_u64_read(int fd, char *name,
+ uint64_t *buf,
+ unsigned long index,
+ unsigned long count)
+{
+ long bytes;
+
+ if (index > ULONG_MAX / 8)
+ fatal("index overflow: %lu\n", index);
+
+ if (lseek(fd, index * 8, SEEK_SET) < 0) {
+ perror(name);
+ exit(EXIT_FAILURE);
+ }
+
+ bytes = read(fd, buf, count * 8);
+ if (bytes < 0) {
+ perror(name);
+ exit(EXIT_FAILURE);
+ }
+ if (bytes % 8)
+ fatal("partial read: %lu bytes\n", bytes);
+
+ return bytes / 8;
+}
+
+static unsigned long kpageflags_read(uint64_t *buf,
+ unsigned long index,
+ unsigned long pages)
+{
+ return do_u64_read(kpageflags_fd, PROC_KPAGEFLAGS, buf, index, pages);
+}
+
+static unsigned long pagemap_read(uint64_t *buf,
+ unsigned long index,
+ unsigned long pages)
+{
+ return do_u64_read(pagemap_fd, "/proc/pid/pagemap", buf, index, pages);
+}
+
+static unsigned long pagemap_pfn(uint64_t val)
+{
+ unsigned long pfn;
+
+ if (val & PM_PRESENT)
+ pfn = PM_PFRAME(val);
+ else
+ pfn = 0;
+
+ return pfn;
+}
+
/*
* page flag names
@@ -255,7 +334,8 @@ static char *page_flag_longname(uint64_t flags)
* page list and summary
*/
-static void show_page_range(unsigned long offset, uint64_t flags)
+static void show_page_range(unsigned long voffset,
+ unsigned long offset, uint64_t flags)
{
static uint64_t flags0;
static unsigned long voff;
@@ -281,7 +361,8 @@ static void show_page_range(unsigned long offset, uint64_t flags)
count = 1;
}
-static void show_page(unsigned long offset, uint64_t flags)
+static void show_page(unsigned long voffset,
+ unsigned long offset, uint64_t flags)
{
if (opt_pid)
printf("%lx\t", voffset);
@@ -362,6 +443,62 @@ static uint64_t well_known_flags(uint64_t flags)
return flags;
}
+static uint64_t kpageflags_flags(uint64_t flags)
+{
+ flags = expand_overloaded_flags(flags);
+
+ if (!opt_raw)
+ flags = well_known_flags(flags);
+
+ return flags;
+}
+
+/*
+ * page actions
+ */
+
+static void prepare_hwpoison_fd(void)
+{
+ char buf[100];
+
+ if (opt_hwpoison && !hwpoison_inject_fd) {
+ sprintf(buf, "%s/corrupt-pfn", hwpoison_debug_fs);
+ hwpoison_inject_fd = checked_open(buf, O_WRONLY);
+ }
+
+ if (opt_unpoison && !hwpoison_forget_fd) {
+ sprintf(buf, "%s/renew-pfn", hwpoison_debug_fs);
+ hwpoison_forget_fd = checked_open(buf, O_WRONLY);
+ }
+}
+
+static int hwpoison_page(unsigned long offset)
+{
+ char buf[100];
+ int len;
+
+ len = sprintf(buf, "0x%lx\n", offset);
+ len = write(hwpoison_inject_fd, buf, len);
+ if (len < 0) {
+ perror("hwpoison inject");
+ return len;
+ }
+ return 0;
+}
+
+static int unpoison_page(unsigned long offset)
+{
+ char buf[100];
+ int len;
+
+ len = sprintf(buf, "0x%lx\n", offset);
+ len = write(hwpoison_forget_fd, buf, len);
+ if (len < 0) {
+ perror("hwpoison forget");
+ return len;
+ }
+ return 0;
+}
/*
* page frame walker
@@ -394,104 +531,83 @@ static int hash_slot(uint64_t flags)
exit(EXIT_FAILURE);
}
-static void add_page(unsigned long offset, uint64_t flags)
+static void add_page(unsigned long voffset,
+ unsigned long offset, uint64_t flags)
{
- flags = expand_overloaded_flags(flags);
-
- if (!opt_raw)
- flags = well_known_flags(flags);
+ flags = kpageflags_flags(flags);
if (!bit_mask_ok(flags))
return;
+ if (opt_hwpoison)
+ hwpoison_page(offset);
+ if (opt_unpoison)
+ unpoison_page(offset);
+
if (opt_list == 1)
- show_page_range(offset, flags);
+ show_page_range(voffset, offset, flags);
else if (opt_list == 2)
- show_page(offset, flags);
+ show_page(voffset, offset, flags);
nr_pages[hash_slot(flags)]++;
total_pages++;
}
-static void walk_pfn(unsigned long index, unsigned long count)
+#define KPAGEFLAGS_BATCH (64 << 10) /* 64k pages */
+static void walk_pfn(unsigned long voffset,
+ unsigned long index,
+ unsigned long count)
{
+ uint64_t buf[KPAGEFLAGS_BATCH];
unsigned long batch;
- unsigned long n;
+ unsigned long pages;
unsigned long i;
- if (index > ULONG_MAX / KPF_BYTES)
- fatal("index overflow: %lu\n", index);
-
- lseek(kpageflags_fd, index * KPF_BYTES, SEEK_SET);
-
while (count) {
- uint64_t kpageflags_buf[KPF_BYTES * PAGES_BATCH];
-
- batch = min_t(unsigned long, count, PAGES_BATCH);
- n = read(kpageflags_fd, kpageflags_buf, batch * KPF_BYTES);
- if (n == 0)
+ batch = min_t(unsigned long, count, KPAGEFLAGS_BATCH);
+ pages = kpageflags_read(buf, index, batch);
+ if (pages == 0)
break;
- if (n < 0) {
- perror(PROC_KPAGEFLAGS);
- exit(EXIT_FAILURE);
- }
- if (n % KPF_BYTES != 0)
- fatal("partial read: %lu bytes\n", n);
- n = n / KPF_BYTES;
+ for (i = 0; i < pages; i++)
+ add_page(voffset + i, index + i, buf[i]);
- for (i = 0; i < n; i++)
- add_page(index + i, kpageflags_buf[i]);
-
- index += batch;
- count -= batch;
+ index += pages;
+ count -= pages;
}
}
-
-#define PAGEMAP_BATCH 4096
-static unsigned long task_pfn(unsigned long pgoff)
+#define PAGEMAP_BATCH (64 << 10)
+static void walk_vma(unsigned long index, unsigned long count)
{
- static uint64_t buf[PAGEMAP_BATCH];
- static unsigned long start;
- static long count;
- uint64_t pfn;
+ uint64_t buf[PAGEMAP_BATCH];
+ unsigned long batch;
+ unsigned long pages;
+ unsigned long pfn;
+ unsigned long i;
- if (pgoff < start || pgoff >= start + count) {
- if (lseek64(pagemap_fd,
- (uint64_t)pgoff * PM_ENTRY_BYTES,
- SEEK_SET) < 0) {
- perror("pagemap seek");
- exit(EXIT_FAILURE);
- }
- count = read(pagemap_fd, buf, sizeof(buf));
- if (count == 0)
- return 0;
- if (count < 0) {
- perror("pagemap read");
- exit(EXIT_FAILURE);
- }
- if (count % PM_ENTRY_BYTES) {
- fatal("pagemap read not aligned.\n");
- exit(EXIT_FAILURE);
- }
- count /= PM_ENTRY_BYTES;
- start = pgoff;
- }
+ while (count) {
+ batch = min_t(unsigned long, count, PAGEMAP_BATCH);
+ pages = pagemap_read(buf, index, batch);
+ if (pages == 0)
+ break;
- pfn = buf[pgoff - start];
- if (pfn & PM_PRESENT)
- pfn = PM_PFRAME(pfn);
- else
- pfn = 0;
+ for (i = 0; i < pages; i++) {
+ pfn = pagemap_pfn(buf[i]);
+ if (pfn)
+ walk_pfn(index + i, pfn, 1);
+ }
- return pfn;
+ index += pages;
+ count -= pages;
+ }
}
static void walk_task(unsigned long index, unsigned long count)
{
- int i = 0;
const unsigned long end = index + count;
+ unsigned long start;
+ int i = 0;
while (index < end) {
@@ -501,15 +617,11 @@ static void walk_task(unsigned long index, unsigned long count)
if (pg_start[i] >= end)
return;
- voffset = max_t(unsigned long, pg_start[i], index);
- index = min_t(unsigned long, pg_end[i], end);
+ start = max_t(unsigned long, pg_start[i], index);
+ index = min_t(unsigned long, pg_end[i], end);
- assert(voffset < index);
- for (; voffset < index; voffset++) {
- unsigned long pfn = task_pfn(voffset);
- if (pfn)
- walk_pfn(pfn, 1);
- }
+ assert(start < index);
+ walk_vma(start, index - start);
}
}
@@ -527,18 +639,14 @@ static void walk_addr_ranges(void)
{
int i;
- kpageflags_fd = open(PROC_KPAGEFLAGS, O_RDONLY);
- if (kpageflags_fd < 0) {
- perror(PROC_KPAGEFLAGS);
- exit(EXIT_FAILURE);
- }
+ kpageflags_fd = checked_open(PROC_KPAGEFLAGS, O_RDONLY);
if (!nr_addr_ranges)
add_addr_range(0, ULONG_MAX);
for (i = 0; i < nr_addr_ranges; i++)
if (!opt_pid)
- walk_pfn(opt_offset[i], opt_size[i]);
+ walk_pfn(0, opt_offset[i], opt_size[i]);
else
walk_task(opt_offset[i], opt_size[i]);
@@ -575,6 +683,8 @@ static void usage(void)
" -l|--list Show page details in ranges\n"
" -L|--list-each Show page details one by one\n"
" -N|--no-summary Don't show summay info\n"
+" -X|--hwpoison hwpoison pages\n"
+" -x|--unpoison unpoison pages\n"
" -h|--help Show this usage message\n"
"addr-spec:\n"
" N one page at offset N (unit: pages)\n"
@@ -624,11 +734,7 @@ static void parse_pid(const char *str)
opt_pid = parse_number(str);
sprintf(buf, "/proc/%d/pagemap", opt_pid);
- pagemap_fd = open(buf, O_RDONLY);
- if (pagemap_fd < 0) {
- perror(buf);
- exit(EXIT_FAILURE);
- }
+ pagemap_fd = checked_open(buf, O_RDONLY);
sprintf(buf, "/proc/%d/maps", opt_pid);
file = fopen(buf, "r");
@@ -788,6 +894,8 @@ static struct option opts[] = {
{ "list" , 0, NULL, 'l' },
{ "list-each" , 0, NULL, 'L' },
{ "no-summary", 0, NULL, 'N' },
+ { "hwpoison" , 0, NULL, 'X' },
+ { "unpoison" , 0, NULL, 'x' },
{ "help" , 0, NULL, 'h' },
{ NULL , 0, NULL, 0 }
};
@@ -799,7 +907,7 @@ int main(int argc, char *argv[])
page_size = getpagesize();
while ((c = getopt_long(argc, argv,
- "rp:f:a:b:lLNh", opts, NULL)) != -1) {
+ "rp:f:a:b:lLNXxh", opts, NULL)) != -1) {
switch (c) {
case 'r':
opt_raw = 1;
@@ -825,6 +933,14 @@ int main(int argc, char *argv[])
case 'N':
opt_no_summary = 1;
break;
+ case 'X':
+ opt_hwpoison = 1;
+ prepare_hwpoison_fd();
+ break;
+ case 'x':
+ opt_unpoison = 1;
+ prepare_hwpoison_fd();
+ break;
case 'h':
usage();
exit(0);
@@ -844,7 +960,7 @@ int main(int argc, char *argv[])
walk_addr_ranges();
if (opt_list == 1)
- show_page_range(0, 0); /* drain the buffer */
+ show_page_range(0, 0, 0); /* drain the buffer */
if (opt_no_summary)
return 0;
diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt
index 600a304a828..df09b9650a8 100644
--- a/Documentation/vm/pagemap.txt
+++ b/Documentation/vm/pagemap.txt
@@ -57,7 +57,9 @@ There are three components to pagemap:
16. COMPOUND_TAIL
16. HUGE
18. UNEVICTABLE
+ 19. HWPOISON
20. NOPAGE
+ 21. KSM
Short descriptions to the page flags:
@@ -86,9 +88,15 @@ Short descriptions to the page flags:
17. HUGE
this is an integral part of a HugeTLB page
+19. HWPOISON
+ hardware detected memory corruption on this page: don't touch the data!
+
20. NOPAGE
no page frame exists at the requested address
+21. KSM
+ identical memory pages dynamically shared between one or more processes
+
[IO related page flags]
1. ERROR IO error occurred
3. UPTODATE page has up-to-date data
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-29 07:59:33 +0000