parisc: PDT: Add full support for memory failure via Page Deallocation Table (PDT)

This patch adds full support to read PDT info on all machine types.  At bootup
the PDT is read and bad memory excluded from usage via memblock_reserve().

Later in the boot process a kernel thread is started (kpdtd) which regularily
checks firmare for new reported bad memory and tries to soft offline pages in
case of correctable errors and to kill processes and exclude such memory in
case of uncorrectable errors via memory_failure().
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/Kconfig

@@ -9,6 +9,7 @@ config PARISC
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_STRICT_KERNEL_RWX
+	select ARCH_SUPPORTS_MEMORY_FAILURE
 	select RTC_CLASS
 	select RTC_DRV_GENERIC
 	select INIT_ALL_POSSIBLE

arch/parisc/kernel/pdt.c

 /*
  *    Page Deallocation Table (PDT) support
  *
- *    The Page Deallocation Table (PDT) holds a table with pointers to bad
- *    memory (broken RAM modules) which is maintained by firmware.
+ *    The Page Deallocation Table (PDT) is maintained by firmware and holds a
+ *    list of memory addresses in which memory errors were detected.
+ *    The list contains both single-bit (correctable) and double-bit
+ *    (uncorrectable) errors.
  *
  *    Copyright 2017 by Helge Deller <deller@gmx.de>
  *
- *    TODO:
- *    - check regularily for new bad memory
- *    - add userspace interface with procfs or sysfs
- *    - increase number of PDT entries dynamically
+ *    possible future enhancements:
+ *    - add userspace interface via procfs or sysfs to clear PDT
  */
 
 #include <linux/memblock.h>
 #include <linux/seq_file.h>
+#include <linux/kthread.h>
 
 #include <asm/pdc.h>
 #include <asm/pdcpat.h>
@@ -24,11 +25,16 @@ enum pdt_access_type {
 	PDT_NONE,
 	PDT_PDC,
 	PDT_PAT_NEW,
-	PDT_PAT_OLD
+	PDT_PAT_CELL
 };
 
 static enum pdt_access_type pdt_type;
 
+/* PDT poll interval: 1 minute if errors, 5 minutes if everything OK. */
+#define PDT_POLL_INTERVAL_DEFAULT	(5*60*HZ)
+#define PDT_POLL_INTERVAL_SHORT		(1*60*HZ)
+static unsigned long pdt_poll_interval = PDT_POLL_INTERVAL_DEFAULT;
+
 /* global PDT status information */
 static struct pdc_mem_retinfo pdt_status;
 
@@ -36,6 +42,21 @@ static struct pdc_mem_retinfo pdt_status;
 #define MAX_PDT_ENTRIES		(MAX_PDT_TABLE_SIZE / sizeof(unsigned long))
 static unsigned long pdt_entry[MAX_PDT_ENTRIES] __page_aligned_bss;
 
+/*
+ * Constants for the pdt_entry format:
+ * A pdt_entry holds the physical address in bits 0-57, bits 58-61 are
+ * reserved, bit 62 is the perm bit and bit 63 is the error_type bit.
+ * The perm bit indicates whether the error have been verified as a permanent
+ * error (value of 1) or has not been verified, and may be transient (value
+ * of 0). The error_type bit indicates whether the error is a single bit error
+ * (value of 1) or a multiple bit error.
+ * On non-PAT machines phys_addr is encoded in bits 0-59 and error_type in bit
+ * 63. Those machines don't provide the perm bit.
+ */
+
+#define PDT_ADDR_PHYS_MASK	(pdt_type != PDT_PDC ? ~0x3f : ~0x0f)
+#define PDT_ADDR_PERM_ERR	(pdt_type != PDT_PDC ? 2UL : 0UL)
+#define PDT_ADDR_SINGLE_ERR	1UL
 
 /* report PDT entries via /proc/meminfo */
 void arch_report_meminfo(struct seq_file *m)
@@ -49,6 +70,68 @@ void arch_report_meminfo(struct seq_file *m)
 			pdt_status.pdt_entries);
 }
 
+static int get_info_pat_new(void)
+{
+	struct pdc_pat_mem_retinfo pat_rinfo;
+	int ret;
+
+	/* newer PAT machines like C8000 report info for all cells */
+	if (is_pdc_pat())
+		ret = pdc_pat_mem_pdt_info(&pat_rinfo);
+	else
+		return PDC_BAD_PROC;
+
+	pdt_status.pdt_size = pat_rinfo.max_pdt_entries;
+	pdt_status.pdt_entries = pat_rinfo.current_pdt_entries;
+	pdt_status.pdt_status = 0;
+	pdt_status.first_dbe_loc = pat_rinfo.first_dbe_loc;
+	pdt_status.good_mem = pat_rinfo.good_mem;
+
+	return ret;
+}
+
+static int get_info_pat_cell(void)
+{
+	struct pdc_pat_mem_cell_pdt_retinfo cell_rinfo;
+	int ret;
+
+	/* older PAT machines like rp5470 report cell info only */
+	if (is_pdc_pat())
+		ret = pdc_pat_mem_pdt_cell_info(&cell_rinfo, parisc_cell_num);
+	else
+		return PDC_BAD_PROC;
+
+	pdt_status.pdt_size = cell_rinfo.max_pdt_entries;
+	pdt_status.pdt_entries = cell_rinfo.current_pdt_entries;
+	pdt_status.pdt_status = 0;
+	pdt_status.first_dbe_loc = cell_rinfo.first_dbe_loc;
+	pdt_status.good_mem = cell_rinfo.good_mem;
+
+	return ret;
+}
+
+static void report_mem_err(unsigned long pde)
+{
+	struct pdc_pat_mem_phys_mem_location loc;
+	unsigned long addr;
+	char dimm_txt[32];
+
+	addr = pde & PDT_ADDR_PHYS_MASK;
+
+	/* show DIMM slot description on PAT machines */
+	if (is_pdc_pat()) {
+		pdc_pat_mem_get_dimm_phys_location(&loc, addr);
+		sprintf(dimm_txt, "DIMM slot %02x, ", loc.dimm_slot);
+	} else
+		dimm_txt[0] = 0;
+
+	pr_warn("PDT: BAD MEMORY at 0x%08lx, %s%s%s-bit error.\n",
+		addr, dimm_txt,
+		pde & PDT_ADDR_PERM_ERR ? "permanent ":"",
+		pde & PDT_ADDR_SINGLE_ERR ? "single":"multi");
+}
+
+
 /*
  * pdc_pdt_init()
  *
@@ -63,18 +146,17 @@ void __init pdc_pdt_init(void)
 	unsigned long entries;
 	struct pdc_mem_read_pdt pdt_read_ret;
 
-	if (is_pdc_pat()) {
-		struct pdc_pat_mem_retinfo pat_rinfo;
-
 	pdt_type = PDT_PAT_NEW;
-		ret = pdc_pat_mem_pdt_info(&pat_rinfo);
-		pdt_status.pdt_size = pat_rinfo.max_pdt_entries;
-		pdt_status.pdt_entries = pat_rinfo.current_pdt_entries;
-		pdt_status.pdt_status = 0;
-		pdt_status.first_dbe_loc = pat_rinfo.first_dbe_loc;
-		pdt_status.good_mem = pat_rinfo.good_mem;
-	} else {
+	ret = get_info_pat_new();
+
+	if (ret != PDC_OK) {
+		pdt_type = PDT_PAT_CELL;
+		ret = get_info_pat_cell();
+	}
+
+	if (ret != PDC_OK) {
 		pdt_type = PDT_PDC;
+		/* non-PAT machines provide the standard PDC call */
 		ret = pdc_mem_pdt_info(&pdt_status);
 	}
 
@@ -86,13 +168,17 @@ void __init pdc_pdt_init(void)
 	}
 
 	entries = pdt_status.pdt_entries;
-	WARN_ON(entries > MAX_PDT_ENTRIES);
+	if (WARN_ON(entries > MAX_PDT_ENTRIES))
+		entries = pdt_status.pdt_entries = MAX_PDT_ENTRIES;
 
-	pr_info("PDT: size %lu, entries %lu, status %lu, dbe_loc 0x%lx,"
-		" good_mem %lu\n",
+	pr_info("PDT: type %s, size %lu, entries %lu, status %lu, dbe_loc 0x%lx,"
+		" good_mem %lu MB\n",
+			pdt_type == PDT_PDC ? __stringify(PDT_PDC) :
+			pdt_type == PDT_PAT_CELL ? __stringify(PDT_PAT_CELL)
+						 : __stringify(PDT_PAT_NEW),
 			pdt_status.pdt_size, pdt_status.pdt_entries,
 			pdt_status.pdt_status, pdt_status.first_dbe_loc,
-			pdt_status.good_mem);
+			pdt_status.good_mem / 1024 / 1024);
 
 	if (entries == 0) {
 		pr_info("PDT: Firmware reports all memory OK.\n");
@@ -112,15 +198,12 @@ void __init pdc_pdt_init(void)
 #ifdef CONFIG_64BIT
 		struct pdc_pat_mem_read_pd_retinfo pat_pret;
 
-		/* try old obsolete PAT firmware function first */
-		pdt_type = PDT_PAT_OLD;
+		if (pdt_type == PDT_PAT_CELL)
 			ret = pdc_pat_mem_read_cell_pdt(&pat_pret, pdt_entry,
 				MAX_PDT_ENTRIES);
-		if (ret != PDC_OK) {
-			pdt_type = PDT_PAT_NEW;
+		else
 			ret = pdc_pat_mem_read_pd_pdt(&pat_pret, pdt_entry,
 				MAX_PDT_TABLE_SIZE, 0);
-		}
 #else
 		ret = PDC_BAD_PROC;
 #endif
@@ -128,27 +211,142 @@ void __init pdc_pdt_init(void)
 
 	if (ret != PDC_OK) {
 		pdt_type = PDT_NONE;
-		pr_debug("PDT type %d, retval = %d\n", pdt_type, ret);
+		pr_warn("PDT: Get PDT entries failed with %d\n", ret);
 		return;
 	}
 
 	for (i = 0; i < pdt_status.pdt_entries; i++) {
-		struct pdc_pat_mem_phys_mem_location loc;
+		report_mem_err(pdt_entry[i]);
+
+		/* mark memory page bad */
+		memblock_reserve(pdt_entry[i] & PAGE_MASK, PAGE_SIZE);
+	}
+}
+
+
+/*
+ * This is the PDT kernel thread main loop.
+ */
+
+static int pdt_mainloop(void *unused)
+{
+	struct pdc_mem_read_pdt pdt_read_ret;
+	struct pdc_pat_mem_read_pd_retinfo pat_pret __maybe_unused;
+	unsigned long old_num_entries;
+	unsigned long *bad_mem_ptr;
+	int num, ret;
+
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		old_num_entries = pdt_status.pdt_entries;
+
+		schedule_timeout(pdt_poll_interval);
+		if (kthread_should_stop())
+			break;
+
+		/* Do we have new PDT entries? */
+		switch (pdt_type) {
+		case PDT_PAT_NEW:
+			ret = get_info_pat_new();
+			break;
+		case PDT_PAT_CELL:
+			ret = get_info_pat_cell();
+			break;
+		default:
+			ret = pdc_mem_pdt_info(&pdt_status);
+			break;
+		}
+
+		if (ret != PDC_OK) {
+			pr_warn("PDT: unexpected failure %d\n", ret);
+			return -EINVAL;
+		}
+
+		/* if no new PDT entries, just wait again */
+		num = pdt_status.pdt_entries - old_num_entries;
+		if (num <= 0)
+			continue;
+
+		/* decrease poll interval in case we found memory errors */
+		if (pdt_status.pdt_entries &&
+			pdt_poll_interval == PDT_POLL_INTERVAL_DEFAULT)
+			pdt_poll_interval = PDT_POLL_INTERVAL_SHORT;
 
-		/* get DIMM slot number */
-		loc.dimm_slot = 0xff;
+		/* limit entries to get */
+		if (num > MAX_PDT_ENTRIES) {
+			num = MAX_PDT_ENTRIES;
+			pdt_status.pdt_entries = old_num_entries + num;
+		}
+
+		/* get new entries */
+		switch (pdt_type) {
 #ifdef CONFIG_64BIT
-		pdc_pat_mem_get_dimm_phys_location(&loc, pdt_entry[i]);
+		case PDT_PAT_CELL:
+			if (pdt_status.pdt_entries > MAX_PDT_ENTRIES) {
+				pr_crit("PDT: too many entries.\n");
+				return -ENOMEM;
+			}
+			ret = pdc_pat_mem_read_cell_pdt(&pat_pret, pdt_entry,
+				MAX_PDT_ENTRIES);
+			bad_mem_ptr = &pdt_entry[old_num_entries];
+			break;
+		case PDT_PAT_NEW:
+			ret = pdc_pat_mem_read_pd_pdt(&pat_pret,
+				pdt_entry,
+				num * sizeof(unsigned long),
+				old_num_entries * sizeof(unsigned long));
+			bad_mem_ptr = &pdt_entry[0];
+			break;
 #endif
+		default:
+			ret = pdc_mem_pdt_read_entries(&pdt_read_ret,
+				pdt_entry);
+			bad_mem_ptr = &pdt_entry[old_num_entries];
+			break;
+		}
 
-		pr_warn("PDT: BAD PAGE #%d at 0x%08lx, "
-			"DIMM slot %02x (error_type = %lu)\n",
-			i,
-			pdt_entry[i] & PAGE_MASK,
-			loc.dimm_slot,
-			pdt_entry[i] & 1);
+		/* report and mark memory broken */
+		while (num--) {
+			unsigned long pde = *bad_mem_ptr++;
+
+			report_mem_err(pde);
+
+#ifdef CONFIG_MEMORY_FAILURE
+			if ((pde & PDT_ADDR_PERM_ERR) ||
+			    ((pde & PDT_ADDR_SINGLE_ERR) == 0))
+				memory_failure(pde >> PAGE_SHIFT, 0, 0);
+			else
+				soft_offline_page(
+					pfn_to_page(pde >> PAGE_SHIFT), 0);
+#else
+			pr_crit("PDT: memory error at 0x%lx ignored.\n"
+				"Rebuild kernel with CONFIG_MEMORY_FAILURE=y "
+				"for real handling.\n",
+				pde & PDT_ADDR_PHYS_MASK);
+#endif
 
-		/* mark memory page bad */
-		memblock_reserve(pdt_entry[i] & PAGE_MASK, PAGE_SIZE);
 		}
+	}
+
+	return 0;
+}
+
+
+static int __init pdt_initcall(void)
+{
+	struct task_struct *kpdtd_task;
+
+	if (pdt_type == PDT_NONE)
+		return -ENODEV;
+
+	kpdtd_task = kthread_create(pdt_mainloop, NULL, "kpdtd");
+	if (IS_ERR(kpdtd_task))
+		return PTR_ERR(kpdtd_task);
+
+	wake_up_process(kpdtd_task);
+
+	return 0;
 }
+
+late_initcall(pdt_initcall);