[RFC PATCH 0/4] Flush nvdimm/pmem to memory before machine restart

[RFC PATCH 0/4] Flush nvdimm/pmem to memory before machine restart

[Mathieu Desnoyers]

Introduce a new pre_restart notifier chain for callbacks that need to
be executed after the system has been made quiescent with
syscore_shutdown(), before machine restart.

Register pre-restart notifiers to flush pmem areas from CPU data cache
to memory on reboot, immediately before restarting the machine. This
ensures all other CPUs are quiescent before the pmem data is flushed to
memory.

The use-case for this new notifier chain is to preserve tracing data
within pmem areas on systems where the BIOS does not clear memory across
warm reboots.

I did an earlier POC that flushed caches on panic/die oops notifiers [1],
but it did not cover the reboot case. I've been made aware that some
distribution vendors have started shipping their own modified version of
my earlier POC patch. This makes a strong argument for upstreaming this
work.

Link: https://lore.kernel.org/linux-kernel/f6067e3e-a2bc-483d-b214-6e3fe6691279@efficios.com/ [1]
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: nvdimm@lists.linux.dev
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org

Mathieu Desnoyers (4):
  kernel/reboot: Introduce pre_restart notifiers
  nvdimm/pmem: Flush to memory before machine restart
  arm64: Invoke pre_restart notifiers
  x86: Invoke pre_restart notifiers

 arch/arm64/kernel/process.c |  2 ++
 arch/x86/kernel/reboot.c    |  7 +++--
 drivers/nvdimm/pmem.c       | 29 ++++++++++++++++++++-
 drivers/nvdimm/pmem.h       |  2 ++
 include/linux/reboot.h      |  4 +++
 kernel/reboot.c             | 51 +++++++++++++++++++++++++++++++++++++
 6 files changed, 92 insertions(+), 3 deletions(-)

-- 
2.39.2

[RFC PATCH 1/4] kernel/reboot: Introduce pre_restart notifiers

[Mathieu Desnoyers]

Introduce a new pre_restart notifier chain for callbacks that need to
be executed after the system has been made quiescent with
syscore_shutdown(), before machine restart.

This pre_restart notifier chain should be invoked on machine restart and
on emergency machine restart.

The use-case for this new notifier chain is to preserve tracing data
within pmem areas on systems where the BIOS does not clear memory across
warm reboots.

Why do we need a new notifier chain ?

1) The reboot and restart_prepare notifiers are called too early in the
   reboot sequence: they are invoked before syscore_shutdown(), which
   leaves other CPUs actively running threads while those notifiers are
   invoked.

2) The "restart" notifier is meant to trigger the actual machine
   restart, and is not meant to be invoked as a last step immediately
   before restart. It is also not always used: some architecture code
   choose to bypass this restart notifier and reboot directly from the
   architecture code.

Wiring up the architecture code to call this notifier chain is left to
follow-up arch-specific patches.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: nvdimm@lists.linux.dev
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
---
 include/linux/reboot.h |  4 ++++
 kernel/reboot.c        | 51 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index abcdde4df697..c7f340e81451 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -50,6 +50,10 @@ extern int register_restart_handler(struct notifier_block *);
 extern int unregister_restart_handler(struct notifier_block *);
 extern void do_kernel_restart(char *cmd);
 
+extern int register_pre_restart_handler(struct notifier_block *);
+extern int unregister_pre_restart_handler(struct notifier_block *);
+extern void do_kernel_pre_restart(char *cmd);
+
 /*
  * Architecture-specific implementations of sys_reboot commands.
  */
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 22c16e2564cc..b7287dd48d35 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -235,6 +235,57 @@ void do_kernel_restart(char *cmd)
 	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
 }
 
+/*
+ *	Notifier list for kernel code which wants to be called immediately
+ *	before restarting the system.
+ */
+static ATOMIC_NOTIFIER_HEAD(pre_restart_handler_list);
+
+/**
+ *	register_pre_restart_handler - Register function to be called in preparation
+ *				       to reset the system
+ *	@nb: Info about handler function to be called
+ *
+ *	Registers a function with code to be called in preparation to restart
+ *	the system.
+ *
+ *	Currently always returns zero, as atomic_notifier_chain_register()
+ *	always returns zero.
+ */
+int register_pre_restart_handler(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&pre_restart_handler_list, nb);
+}
+EXPORT_SYMBOL(register_pre_restart_handler);
+
+/**
+ *	unregister_pre_restart_handler - Unregister previously registered
+ *					 pre-restart handler
+ *	@nb: Hook to be unregistered
+ *
+ *	Unregisters a previously registered pre-restart handler function.
+ *
+ *	Returns zero on success, or %-ENOENT on failure.
+ */
+int unregister_pre_restart_handler(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_unregister(&pre_restart_handler_list, nb);
+}
+EXPORT_SYMBOL(unregister_pre_restart_handler);
+
+/**
+ *	do_kernel_pre_restart - Execute kernel pre-restart handler call chain
+ *
+ *	Calls functions registered with register_pre_restart_handler.
+ *
+ *	Expected to be called from machine_restart and
+ *	machine_emergency_restart before invoking the restart handlers.
+ */
+void do_kernel_pre_restart(char *cmd)
+{
+	atomic_notifier_call_chain(&pre_restart_handler_list, reboot_mode, cmd);
+}
+
 void migrate_to_reboot_cpu(void)
 {
 	/* The boot cpu is always logical cpu 0 */
-- 
2.39.2

[RFC PATCH 2/4] nvdimm/pmem: Flush to memory before machine restart

[Mathieu Desnoyers]

Register pre-restart notifiers to flush pmem areas from CPU data cache
to memory on reboot, immediately before restarting the machine. This
ensures all other CPUs are quiescent before the pmem data is flushed to
memory.

I did an earlier POC that flushed caches on panic/die oops notifiers [1],
but it did not cover the reboot case. I've been made aware that some
distribution vendors have started shipping their own modified version of
my earlier POC patch. This makes a strong argument for upstreaming this
work.

Use the newly introduced "pre-restart" notifiers to flush pmem data to
memory immediately before machine restart.

Delta from my POC patch [1]:

Looking at the panic() code, it invokes emergency_restart() to restart
the machine, which uses the new pre-restart notifiers. There is
therefore no need to hook into panic handlers explicitly.

Looking at the die notifiers, those don't actually end up triggering
a machine restart, so it does not appear to be relevant to flush pmem
to memory there. I must admit I originally looked at how ftrace hooked
into panic/die-oops handlers for its ring buffers, but the use-case it
different here: we only want to cover machine restart use-cases.

Link: https://lore.kernel.org/linux-kernel/f6067e3e-a2bc-483d-b214-6e3fe6691279@efficios.com/ [1]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: nvdimm@lists.linux.dev
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
---
 drivers/nvdimm/pmem.c | 29 ++++++++++++++++++++++++++++-
 drivers/nvdimm/pmem.h |  2 ++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 598fe2e89bda..bf1d187a9dca 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -26,12 +26,16 @@
 #include <linux/dax.h>
 #include <linux/nd.h>
 #include <linux/mm.h>
+#include <linux/reboot.h>
 #include <asm/cacheflush.h>
 #include "pmem.h"
 #include "btt.h"
 #include "pfn.h"
 #include "nd.h"
 
+static int pmem_pre_restart_handler(struct notifier_block *self,
+		unsigned long ev, void *unused);
+
 static struct device *to_dev(struct pmem_device *pmem)
 {
 	/*
@@ -423,6 +427,7 @@ static void pmem_release_disk(void *__pmem)
 {
 	struct pmem_device *pmem = __pmem;
 
+	unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
 	dax_remove_host(pmem->disk);
 	kill_dax(pmem->dax_dev);
 	put_dax(pmem->dax_dev);
@@ -575,9 +580,14 @@ static int pmem_attach_disk(struct device *dev,
 			goto out_cleanup_dax;
 		dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
 	}
-	rc = device_add_disk(dev, disk, pmem_attribute_groups);
+	pmem->pre_restart_notifier.notifier_call = pmem_pre_restart_handler;
+	pmem->pre_restart_notifier.priority = 0;
+	rc = register_pre_restart_notifier(&pmem->pre_restart_notifier);
 	if (rc)
 		goto out_remove_host;
+	rc = device_add_disk(dev, disk, pmem_attribute_groups);
+	if (rc)
+		goto out_unregister_reboot;
 	if (devm_add_action_or_reset(dev, pmem_release_disk, pmem))
 		return -ENOMEM;
 
@@ -589,6 +599,8 @@ static int pmem_attach_disk(struct device *dev,
 		dev_warn(dev, "'badblocks' notification disabled\n");
 	return 0;
 
+out_unregister_pre_restart:
+	unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
 out_remove_host:
 	dax_remove_host(pmem->disk);
 out_cleanup_dax:
@@ -751,6 +763,21 @@ static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
 	}
 }
 
+/*
+ * For volatile memory use-cases where explicit flushing of the data cache is
+ * not useful after stores, the pmem reboot notifier is called on preparation
+ * for restart to make sure the content of the pmem memory area is flushed from
+ * data cache to memory, so it can be preserved across warm reboot.
+ */
+static int pmem_pre_restart_handler(struct notifier_block *self,
+		unsigned long ev, void *unused)
+{
+	struct pmem_device *pmem = container_of(self, struct pmem_device, pre_restart_notifier);
+
+	arch_wb_cache_pmem(pmem->virt_addr, pmem->size);
+	return NOTIFY_DONE;
+}
+
 MODULE_ALIAS("pmem");
 MODULE_ALIAS_ND_DEVICE(ND_DEVICE_NAMESPACE_IO);
 MODULE_ALIAS_ND_DEVICE(ND_DEVICE_NAMESPACE_PMEM);
diff --git a/drivers/nvdimm/pmem.h b/drivers/nvdimm/pmem.h
index 392b0b38acb9..b8a2a518cf82 100644
--- a/drivers/nvdimm/pmem.h
+++ b/drivers/nvdimm/pmem.h
@@ -4,6 +4,7 @@
 #include <linux/page-flags.h>
 #include <linux/badblocks.h>
 #include <linux/memremap.h>
+#include <linux/notifier.h>
 #include <linux/types.h>
 #include <linux/pfn_t.h>
 #include <linux/fs.h>
@@ -27,6 +28,7 @@ struct pmem_device {
 	struct dax_device	*dax_dev;
 	struct gendisk		*disk;
 	struct dev_pagemap	pgmap;
+	struct notifier_block	pre_restart_notifier;
 };
 
 long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
-- 
2.39.2

Re: [RFC PATCH 2/4] nvdimm/pmem: Flush to memory before machine restart

[kernel test robot]

Hi Mathieu,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on nvdimm/libnvdimm-for-next]
[also build test ERROR on arm64/for-next/core linus/master v6.10-rc4 next-20240618]
[cannot apply to nvdimm/dax-misc tip/x86/core rostedt-trace/for-next rostedt-trace/for-next-urgent]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Mathieu-Desnoyers/kernel-reboot-Introduce-pre_restart-notifiers/20240618-235520
base:   https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git libnvdimm-for-next
patch link:    https://lore.kernel.org/r/20240618154157.334602-3-mathieu.desnoyers%40efficios.com
patch subject: [RFC PATCH 2/4] nvdimm/pmem: Flush to memory before machine restart
config: x86_64-randconfig-014-20240619 (https://download.01.org/0day-ci/archive/20240619/202406192330.5Z2ExUMs-lkp@intel.com/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240619/202406192330.5Z2ExUMs-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406192330.5Z2ExUMs-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

>> drivers/nvdimm/pmem.c:430:2: error: call to undeclared function 'unregister_pre_restart_notifier'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     430 |         unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
         |         ^
   drivers/nvdimm/pmem.c:430:2: note: did you mean 'unregister_pre_restart_handler'?
   include/linux/reboot.h:54:12: note: 'unregister_pre_restart_handler' declared here
      54 | extern int unregister_pre_restart_handler(struct notifier_block *);
         |            ^
>> drivers/nvdimm/pmem.c:585:7: error: call to undeclared function 'register_pre_restart_notifier'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     585 |         rc = register_pre_restart_notifier(&pmem->pre_restart_notifier);
         |              ^
   drivers/nvdimm/pmem.c:585:7: note: did you mean 'register_pre_restart_handler'?
   include/linux/reboot.h:53:12: note: 'register_pre_restart_handler' declared here
      53 | extern int register_pre_restart_handler(struct notifier_block *);
         |            ^
   drivers/nvdimm/pmem.c:603:2: error: call to undeclared function 'unregister_pre_restart_notifier'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     603 |         unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
         |         ^
>> drivers/nvdimm/pmem.c:590:8: error: use of undeclared label 'out_unregister_reboot'
     590 |                 goto out_unregister_reboot;
         |                      ^
>> drivers/nvdimm/pmem.c:602:1: warning: unused label 'out_unregister_pre_restart' [-Wunused-label]
     602 | out_unregister_pre_restart:
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 warning and 4 errors generated.


vim +/unregister_pre_restart_notifier +430 drivers/nvdimm/pmem.c

   425	
   426	static void pmem_release_disk(void *__pmem)
   427	{
   428		struct pmem_device *pmem = __pmem;
   429	
 > 430		unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
   431		dax_remove_host(pmem->disk);
   432		kill_dax(pmem->dax_dev);
   433		put_dax(pmem->dax_dev);
   434		del_gendisk(pmem->disk);
   435	
   436		put_disk(pmem->disk);
   437	}
   438	
   439	static int pmem_pagemap_memory_failure(struct dev_pagemap *pgmap,
   440			unsigned long pfn, unsigned long nr_pages, int mf_flags)
   441	{
   442		struct pmem_device *pmem =
   443				container_of(pgmap, struct pmem_device, pgmap);
   444		u64 offset = PFN_PHYS(pfn) - pmem->phys_addr - pmem->data_offset;
   445		u64 len = nr_pages << PAGE_SHIFT;
   446	
   447		return dax_holder_notify_failure(pmem->dax_dev, offset, len, mf_flags);
   448	}
   449	
   450	static const struct dev_pagemap_ops fsdax_pagemap_ops = {
   451		.memory_failure		= pmem_pagemap_memory_failure,
   452	};
   453	
   454	static int pmem_attach_disk(struct device *dev,
   455			struct nd_namespace_common *ndns)
   456	{
   457		struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
   458		struct nd_region *nd_region = to_nd_region(dev->parent);
   459		struct queue_limits lim = {
   460			.logical_block_size	= pmem_sector_size(ndns),
   461			.physical_block_size	= PAGE_SIZE,
   462			.max_hw_sectors		= UINT_MAX,
   463		};
   464		int nid = dev_to_node(dev), fua;
   465		struct resource *res = &nsio->res;
   466		struct range bb_range;
   467		struct nd_pfn *nd_pfn = NULL;
   468		struct dax_device *dax_dev;
   469		struct nd_pfn_sb *pfn_sb;
   470		struct pmem_device *pmem;
   471		struct request_queue *q;
   472		struct gendisk *disk;
   473		void *addr;
   474		int rc;
   475	
   476		pmem = devm_kzalloc(dev, sizeof(*pmem), GFP_KERNEL);
   477		if (!pmem)
   478			return -ENOMEM;
   479	
   480		rc = devm_namespace_enable(dev, ndns, nd_info_block_reserve());
   481		if (rc)
   482			return rc;
   483	
   484		/* while nsio_rw_bytes is active, parse a pfn info block if present */
   485		if (is_nd_pfn(dev)) {
   486			nd_pfn = to_nd_pfn(dev);
   487			rc = nvdimm_setup_pfn(nd_pfn, &pmem->pgmap);
   488			if (rc)
   489				return rc;
   490		}
   491	
   492		/* we're attaching a block device, disable raw namespace access */
   493		devm_namespace_disable(dev, ndns);
   494	
   495		dev_set_drvdata(dev, pmem);
   496		pmem->phys_addr = res->start;
   497		pmem->size = resource_size(res);
   498		fua = nvdimm_has_flush(nd_region);
   499		if (!IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) || fua < 0) {
   500			dev_warn(dev, "unable to guarantee persistence of writes\n");
   501			fua = 0;
   502		}
   503	
   504		if (!devm_request_mem_region(dev, res->start, resource_size(res),
   505					dev_name(&ndns->dev))) {
   506			dev_warn(dev, "could not reserve region %pR\n", res);
   507			return -EBUSY;
   508		}
   509	
   510		disk = blk_alloc_disk(&lim, nid);
   511		if (IS_ERR(disk))
   512			return PTR_ERR(disk);
   513		q = disk->queue;
   514	
   515		pmem->disk = disk;
   516		pmem->pgmap.owner = pmem;
   517		pmem->pfn_flags = PFN_DEV;
   518		if (is_nd_pfn(dev)) {
   519			pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
   520			pmem->pgmap.ops = &fsdax_pagemap_ops;
   521			addr = devm_memremap_pages(dev, &pmem->pgmap);
   522			pfn_sb = nd_pfn->pfn_sb;
   523			pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
   524			pmem->pfn_pad = resource_size(res) -
   525				range_len(&pmem->pgmap.range);
   526			pmem->pfn_flags |= PFN_MAP;
   527			bb_range = pmem->pgmap.range;
   528			bb_range.start += pmem->data_offset;
   529		} else if (pmem_should_map_pages(dev)) {
   530			pmem->pgmap.range.start = res->start;
   531			pmem->pgmap.range.end = res->end;
   532			pmem->pgmap.nr_range = 1;
   533			pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
   534			pmem->pgmap.ops = &fsdax_pagemap_ops;
   535			addr = devm_memremap_pages(dev, &pmem->pgmap);
   536			pmem->pfn_flags |= PFN_MAP;
   537			bb_range = pmem->pgmap.range;
   538		} else {
   539			addr = devm_memremap(dev, pmem->phys_addr,
   540					pmem->size, ARCH_MEMREMAP_PMEM);
   541			bb_range.start =  res->start;
   542			bb_range.end = res->end;
   543		}
   544	
   545		if (IS_ERR(addr)) {
   546			rc = PTR_ERR(addr);
   547			goto out;
   548		}
   549		pmem->virt_addr = addr;
   550	
   551		blk_queue_write_cache(q, true, fua);
   552		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
   553		blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, q);
   554		if (pmem->pfn_flags & PFN_MAP)
   555			blk_queue_flag_set(QUEUE_FLAG_DAX, q);
   556	
   557		disk->fops		= &pmem_fops;
   558		disk->private_data	= pmem;
   559		nvdimm_namespace_disk_name(ndns, disk->disk_name);
   560		set_capacity(disk, (pmem->size - pmem->pfn_pad - pmem->data_offset)
   561				/ 512);
   562		if (devm_init_badblocks(dev, &pmem->bb))
   563			return -ENOMEM;
   564		nvdimm_badblocks_populate(nd_region, &pmem->bb, &bb_range);
   565		disk->bb = &pmem->bb;
   566	
   567		dax_dev = alloc_dax(pmem, &pmem_dax_ops);
   568		if (IS_ERR(dax_dev)) {
   569			rc = PTR_ERR(dax_dev);
   570			if (rc != -EOPNOTSUPP)
   571				goto out;
   572		} else {
   573			set_dax_nocache(dax_dev);
   574			set_dax_nomc(dax_dev);
   575			if (is_nvdimm_sync(nd_region))
   576				set_dax_synchronous(dax_dev);
   577			pmem->dax_dev = dax_dev;
   578			rc = dax_add_host(dax_dev, disk);
   579			if (rc)
   580				goto out_cleanup_dax;
   581			dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
   582		}
   583		pmem->pre_restart_notifier.notifier_call = pmem_pre_restart_handler;
   584		pmem->pre_restart_notifier.priority = 0;
 > 585		rc = register_pre_restart_notifier(&pmem->pre_restart_notifier);
   586		if (rc)
   587			goto out_remove_host;
   588		rc = device_add_disk(dev, disk, pmem_attribute_groups);
   589		if (rc)
 > 590			goto out_unregister_reboot;
   591		if (devm_add_action_or_reset(dev, pmem_release_disk, pmem))
   592			return -ENOMEM;
   593	
   594		nvdimm_check_and_set_ro(disk);
   595	
   596		pmem->bb_state = sysfs_get_dirent(disk_to_dev(disk)->kobj.sd,
   597						  "badblocks");
   598		if (!pmem->bb_state)
   599			dev_warn(dev, "'badblocks' notification disabled\n");
   600		return 0;
   601	
 > 602	out_unregister_pre_restart:
   603		unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
   604	out_remove_host:
   605		dax_remove_host(pmem->disk);
   606	out_cleanup_dax:
   607		kill_dax(pmem->dax_dev);
   608		put_dax(pmem->dax_dev);
   609	out:
   610		put_disk(pmem->disk);
   611		return rc;
   612	}
   613	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [RFC PATCH 2/4] nvdimm/pmem: Flush to memory before machine restart

[kernel test robot]

Hi Mathieu,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on nvdimm/libnvdimm-for-next]
[also build test ERROR on arm64/for-next/core linus/master v6.10-rc4 next-20240618]
[cannot apply to nvdimm/dax-misc tip/x86/core rostedt-trace/for-next rostedt-trace/for-next-urgent]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Mathieu-Desnoyers/kernel-reboot-Introduce-pre_restart-notifiers/20240618-235520
base:   https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git libnvdimm-for-next
patch link:    https://lore.kernel.org/r/20240618154157.334602-3-mathieu.desnoyers%40efficios.com
patch subject: [RFC PATCH 2/4] nvdimm/pmem: Flush to memory before machine restart
config: x86_64-buildonly-randconfig-003-20240619 (https://download.01.org/0day-ci/archive/20240620/202406200157.cl4DjMkB-lkp@intel.com/config)
compiler: gcc-11 (Ubuntu 11.4.0-4ubuntu1) 11.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240620/202406200157.cl4DjMkB-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406200157.cl4DjMkB-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

   drivers/nvdimm/pmem.c: In function 'pmem_release_disk':
>> drivers/nvdimm/pmem.c:430:9: error: implicit declaration of function 'unregister_pre_restart_notifier'; did you mean 'unregister_pre_restart_handler'? [-Werror=implicit-function-declaration]
     430 |         unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         |         unregister_pre_restart_handler
   drivers/nvdimm/pmem.c: In function 'pmem_attach_disk':
>> drivers/nvdimm/pmem.c:585:14: error: implicit declaration of function 'register_pre_restart_notifier'; did you mean 'register_pre_restart_handler'? [-Werror=implicit-function-declaration]
     585 |         rc = register_pre_restart_notifier(&pmem->pre_restart_notifier);
         |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         |              register_pre_restart_handler
>> drivers/nvdimm/pmem.c:602:1: warning: label 'out_unregister_pre_restart' defined but not used [-Wunused-label]
     602 | out_unregister_pre_restart:
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/nvdimm/pmem.c:590:17: error: label 'out_unregister_reboot' used but not defined
     590 |                 goto out_unregister_reboot;
         |                 ^~~~
   cc1: some warnings being treated as errors


vim +430 drivers/nvdimm/pmem.c

   425	
   426	static void pmem_release_disk(void *__pmem)
   427	{
   428		struct pmem_device *pmem = __pmem;
   429	
 > 430		unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
   431		dax_remove_host(pmem->disk);
   432		kill_dax(pmem->dax_dev);
   433		put_dax(pmem->dax_dev);
   434		del_gendisk(pmem->disk);
   435	
   436		put_disk(pmem->disk);
   437	}
   438	
   439	static int pmem_pagemap_memory_failure(struct dev_pagemap *pgmap,
   440			unsigned long pfn, unsigned long nr_pages, int mf_flags)
   441	{
   442		struct pmem_device *pmem =
   443				container_of(pgmap, struct pmem_device, pgmap);
   444		u64 offset = PFN_PHYS(pfn) - pmem->phys_addr - pmem->data_offset;
   445		u64 len = nr_pages << PAGE_SHIFT;
   446	
   447		return dax_holder_notify_failure(pmem->dax_dev, offset, len, mf_flags);
   448	}
   449	
   450	static const struct dev_pagemap_ops fsdax_pagemap_ops = {
   451		.memory_failure		= pmem_pagemap_memory_failure,
   452	};
   453	
   454	static int pmem_attach_disk(struct device *dev,
   455			struct nd_namespace_common *ndns)
   456	{
   457		struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
   458		struct nd_region *nd_region = to_nd_region(dev->parent);
   459		struct queue_limits lim = {
   460			.logical_block_size	= pmem_sector_size(ndns),
   461			.physical_block_size	= PAGE_SIZE,
   462			.max_hw_sectors		= UINT_MAX,
   463		};
   464		int nid = dev_to_node(dev), fua;
   465		struct resource *res = &nsio->res;
   466		struct range bb_range;
   467		struct nd_pfn *nd_pfn = NULL;
   468		struct dax_device *dax_dev;
   469		struct nd_pfn_sb *pfn_sb;
   470		struct pmem_device *pmem;
   471		struct request_queue *q;
   472		struct gendisk *disk;
   473		void *addr;
   474		int rc;
   475	
   476		pmem = devm_kzalloc(dev, sizeof(*pmem), GFP_KERNEL);
   477		if (!pmem)
   478			return -ENOMEM;
   479	
   480		rc = devm_namespace_enable(dev, ndns, nd_info_block_reserve());
   481		if (rc)
   482			return rc;
   483	
   484		/* while nsio_rw_bytes is active, parse a pfn info block if present */
   485		if (is_nd_pfn(dev)) {
   486			nd_pfn = to_nd_pfn(dev);
   487			rc = nvdimm_setup_pfn(nd_pfn, &pmem->pgmap);
   488			if (rc)
   489				return rc;
   490		}
   491	
   492		/* we're attaching a block device, disable raw namespace access */
   493		devm_namespace_disable(dev, ndns);
   494	
   495		dev_set_drvdata(dev, pmem);
   496		pmem->phys_addr = res->start;
   497		pmem->size = resource_size(res);
   498		fua = nvdimm_has_flush(nd_region);
   499		if (!IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) || fua < 0) {
   500			dev_warn(dev, "unable to guarantee persistence of writes\n");
   501			fua = 0;
   502		}
   503	
   504		if (!devm_request_mem_region(dev, res->start, resource_size(res),
   505					dev_name(&ndns->dev))) {
   506			dev_warn(dev, "could not reserve region %pR\n", res);
   507			return -EBUSY;
   508		}
   509	
   510		disk = blk_alloc_disk(&lim, nid);
   511		if (IS_ERR(disk))
   512			return PTR_ERR(disk);
   513		q = disk->queue;
   514	
   515		pmem->disk = disk;
   516		pmem->pgmap.owner = pmem;
   517		pmem->pfn_flags = PFN_DEV;
   518		if (is_nd_pfn(dev)) {
   519			pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
   520			pmem->pgmap.ops = &fsdax_pagemap_ops;
   521			addr = devm_memremap_pages(dev, &pmem->pgmap);
   522			pfn_sb = nd_pfn->pfn_sb;
   523			pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
   524			pmem->pfn_pad = resource_size(res) -
   525				range_len(&pmem->pgmap.range);
   526			pmem->pfn_flags |= PFN_MAP;
   527			bb_range = pmem->pgmap.range;
   528			bb_range.start += pmem->data_offset;
   529		} else if (pmem_should_map_pages(dev)) {
   530			pmem->pgmap.range.start = res->start;
   531			pmem->pgmap.range.end = res->end;
   532			pmem->pgmap.nr_range = 1;
   533			pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
   534			pmem->pgmap.ops = &fsdax_pagemap_ops;
   535			addr = devm_memremap_pages(dev, &pmem->pgmap);
   536			pmem->pfn_flags |= PFN_MAP;
   537			bb_range = pmem->pgmap.range;
   538		} else {
   539			addr = devm_memremap(dev, pmem->phys_addr,
   540					pmem->size, ARCH_MEMREMAP_PMEM);
   541			bb_range.start =  res->start;
   542			bb_range.end = res->end;
   543		}
   544	
   545		if (IS_ERR(addr)) {
   546			rc = PTR_ERR(addr);
   547			goto out;
   548		}
   549		pmem->virt_addr = addr;
   550	
   551		blk_queue_write_cache(q, true, fua);
   552		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
   553		blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, q);
   554		if (pmem->pfn_flags & PFN_MAP)
   555			blk_queue_flag_set(QUEUE_FLAG_DAX, q);
   556	
   557		disk->fops		= &pmem_fops;
   558		disk->private_data	= pmem;
   559		nvdimm_namespace_disk_name(ndns, disk->disk_name);
   560		set_capacity(disk, (pmem->size - pmem->pfn_pad - pmem->data_offset)
   561				/ 512);
   562		if (devm_init_badblocks(dev, &pmem->bb))
   563			return -ENOMEM;
   564		nvdimm_badblocks_populate(nd_region, &pmem->bb, &bb_range);
   565		disk->bb = &pmem->bb;
   566	
   567		dax_dev = alloc_dax(pmem, &pmem_dax_ops);
   568		if (IS_ERR(dax_dev)) {
   569			rc = PTR_ERR(dax_dev);
   570			if (rc != -EOPNOTSUPP)
   571				goto out;
   572		} else {
   573			set_dax_nocache(dax_dev);
   574			set_dax_nomc(dax_dev);
   575			if (is_nvdimm_sync(nd_region))
   576				set_dax_synchronous(dax_dev);
   577			pmem->dax_dev = dax_dev;
   578			rc = dax_add_host(dax_dev, disk);
   579			if (rc)
   580				goto out_cleanup_dax;
   581			dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
   582		}
   583		pmem->pre_restart_notifier.notifier_call = pmem_pre_restart_handler;
   584		pmem->pre_restart_notifier.priority = 0;
 > 585		rc = register_pre_restart_notifier(&pmem->pre_restart_notifier);
   586		if (rc)
   587			goto out_remove_host;
   588		rc = device_add_disk(dev, disk, pmem_attribute_groups);
   589		if (rc)
 > 590			goto out_unregister_reboot;
   591		if (devm_add_action_or_reset(dev, pmem_release_disk, pmem))
   592			return -ENOMEM;
   593	
   594		nvdimm_check_and_set_ro(disk);
   595	
   596		pmem->bb_state = sysfs_get_dirent(disk_to_dev(disk)->kobj.sd,
   597						  "badblocks");
   598		if (!pmem->bb_state)
   599			dev_warn(dev, "'badblocks' notification disabled\n");
   600		return 0;
   601	
 > 602	out_unregister_pre_restart:
   603		unregister_pre_restart_notifier(&pmem->pre_restart_notifier);
   604	out_remove_host:
   605		dax_remove_host(pmem->disk);
   606	out_cleanup_dax:
   607		kill_dax(pmem->dax_dev);
   608		put_dax(pmem->dax_dev);
   609	out:
   610		put_disk(pmem->disk);
   611		return rc;
   612	}
   613	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[RFC PATCH 3/4] arm64: Invoke pre_restart notifiers

[Mathieu Desnoyers]

Invoke the pre_restart notifiers after shutdown, before machine restart.
This allows preserving pmem memory across warm reboots.

Invoke the pre_restart notifiers before emergency machine restart as
well to cover the panic() scenario.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: nvdimm@lists.linux.dev
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
---
 arch/arm64/kernel/process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 4ae31b7af6c3..4a27397617fb 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -129,6 +129,8 @@ void machine_restart(char *cmd)
 	local_irq_disable();
 	smp_send_stop();
 
+	do_kernel_pre_restart(cmd);
+
 	/*
 	 * UpdateCapsule() depends on the system being reset via
 	 * ResetSystem().
-- 
2.39.2

[RFC PATCH 4/4] x86: Invoke pre_restart notifiers

[Mathieu Desnoyers]

Invoke the pre_restart notifiers after shutdown, before machine restart.
This allows preserving pmem memory across warm reboots.

Invoke the pre_restart notifiers on emergency_machine_restart to cover
the panic() scenario.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: nvdimm@lists.linux.dev
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
 arch/x86/kernel/reboot.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index f3130f762784..222619fa63c6 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -631,8 +631,10 @@ static void native_machine_emergency_restart(void)
 	int orig_reboot_type = reboot_type;
 	unsigned short mode;
 
-	if (reboot_emergency)
+	if (reboot_emergency) {
+		do_kernel_pre_restart(NULL);
 		emergency_reboot_disable_virtualization();
+	}
 
 	tboot_shutdown(TB_SHUTDOWN_REBOOT);
 
@@ -760,12 +762,13 @@ static void __machine_emergency_restart(int emergency)
 	machine_ops.emergency_restart();
 }
 
-static void native_machine_restart(char *__unused)
+static void native_machine_restart(char *cmd)
 {
 	pr_notice("machine restart\n");
 
 	if (!reboot_force)
 		machine_shutdown();
+	do_kernel_pre_restart(cmd);
 	__machine_emergency_restart(0);
 }
 
-- 
2.39.2