1 files changed, 399 insertions, 0 deletions
diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c
new file mode 100644
index 000000000000..27f49f5fd358
--- /dev/null
+++ b/drivers/s390/char/sclp_mem.c
@@ -0,0 +1,399 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Memory hotplug support via sclp
+ *
+ * Copyright IBM Corp. 2025
+ */
+
+#define KMSG_COMPONENT "sclp_mem"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/cpufeature.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/memory.h>
+#include <linux/memory_hotplug.h>
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/slab.h>
+#include <asm/facility.h>
+#include <asm/page.h>
+#include <asm/page-states.h>
+#include <asm/sclp.h>
+
+#include "sclp.h"
+
+#define SCLP_CMDW_ASSIGN_STORAGE		0x000d0001
+#define SCLP_CMDW_UNASSIGN_STORAGE		0x000c0001
+
+static DEFINE_MUTEX(sclp_mem_mutex);
+static LIST_HEAD(sclp_mem_list);
+static u8 sclp_max_storage_id;
+static DECLARE_BITMAP(sclp_storage_ids, 256);
+
+struct memory_increment {
+	struct list_head list;
+	u16 rn;
+	int standby;
+};
+
+struct assign_storage_sccb {
+	struct sccb_header header;
+	u16 rn;
+} __packed;
+
+struct attach_storage_sccb {
+	struct sccb_header header;
+	u16 :16;
+	u16 assigned;
+	u32 :32;
+	u32 entries[];
+} __packed;
+
+int arch_get_memory_phys_device(unsigned long start_pfn)
+{
+	if (!sclp.rzm)
+		return 0;
+	return PFN_PHYS(start_pfn) >> ilog2(sclp.rzm);
+}
+
+static unsigned long rn2addr(u16 rn)
+{
+	return (unsigned long)(rn - 1) * sclp.rzm;
+}
+
+static int do_assign_storage(sclp_cmdw_t cmd, u16 rn)
+{
+	struct assign_storage_sccb *sccb;
+	int rc;
+
+	sccb = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+	if (!sccb)
+		return -ENOMEM;
+	sccb->header.length = PAGE_SIZE;
+	sccb->rn = rn;
+	rc = sclp_sync_request_timeout(cmd, sccb, SCLP_QUEUE_INTERVAL);
+	if (rc)
+		goto out;
+	switch (sccb->header.response_code) {
+	case 0x0020:
+	case 0x0120:
+		break;
+	default:
+		pr_warn("assign storage failed (cmd=0x%08x, response=0x%04x, rn=0x%04x)\n",
+			cmd, sccb->header.response_code, rn);
+		rc = -EIO;
+		break;
+	}
+out:
+	free_page((unsigned long)sccb);
+	return rc;
+}
+
+static int sclp_assign_storage(u16 rn)
+{
+	unsigned long start;
+	int rc;
+
+	rc = do_assign_storage(SCLP_CMDW_ASSIGN_STORAGE, rn);
+	if (rc)
+		return rc;
+	start = rn2addr(rn);
+	storage_key_init_range(start, start + sclp.rzm);
+	return 0;
+}
+
+static int sclp_unassign_storage(u16 rn)
+{
+	return do_assign_storage(SCLP_CMDW_UNASSIGN_STORAGE, rn);
+}
+
+static int sclp_attach_storage(u8 id)
+{
+	struct attach_storage_sccb *sccb;
+	int rc, i;
+
+	sccb = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+	if (!sccb)
+		return -ENOMEM;
+	sccb->header.length = PAGE_SIZE;
+	sccb->header.function_code = 0x40;
+	rc = sclp_sync_request_timeout(0x00080001 | id << 8, sccb,
+				       SCLP_QUEUE_INTERVAL);
+	if (rc)
+		goto out;
+	switch (sccb->header.response_code) {
+	case 0x0020:
+		set_bit(id, sclp_storage_ids);
+		for (i = 0; i < sccb->assigned; i++) {
+			if (sccb->entries[i])
+				sclp_unassign_storage(sccb->entries[i] >> 16);
+		}
+		break;
+	default:
+		rc = -EIO;
+		break;
+	}
+out:
+	free_page((unsigned long)sccb);
+	return rc;
+}
+
+static int sclp_mem_change_state(unsigned long start, unsigned long size,
+				 int online)
+{
+	struct memory_increment *incr;
+	unsigned long istart;
+	int rc = 0;
+
+	list_for_each_entry(incr, &sclp_mem_list, list) {
+		istart = rn2addr(incr->rn);
+		if (start + size - 1 < istart)
+			break;
+		if (start > istart + sclp.rzm - 1)
+			continue;
+		if (online)
+			rc |= sclp_assign_storage(incr->rn);
+		else
+			sclp_unassign_storage(incr->rn);
+		if (rc == 0)
+			incr->standby = online ? 0 : 1;
+	}
+	return rc ? -EIO : 0;
+}
+
+static bool contains_standby_increment(unsigned long start, unsigned long end)
+{
+	struct memory_increment *incr;
+	unsigned long istart;
+
+	list_for_each_entry(incr, &sclp_mem_list, list) {
+		istart = rn2addr(incr->rn);
+		if (end - 1 < istart)
+			continue;
+		if (start > istart + sclp.rzm - 1)
+			continue;
+		if (incr->standby)
+			return true;
+	}
+	return false;
+}
+
+static int sclp_mem_notifier(struct notifier_block *nb,
+			     unsigned long action, void *data)
+{
+	unsigned long start, size;
+	struct memory_notify *arg;
+	unsigned char id;
+	int rc = 0;
+
+	arg = data;
+	start = arg->start_pfn << PAGE_SHIFT;
+	size = arg->nr_pages << PAGE_SHIFT;
+	mutex_lock(&sclp_mem_mutex);
+	for_each_clear_bit(id, sclp_storage_ids, sclp_max_storage_id + 1)
+		sclp_attach_storage(id);
+	switch (action) {
+	case MEM_GOING_OFFLINE:
+		/*
+		 * Do not allow to set memory blocks offline that contain
+		 * standby memory. This is done to simplify the "memory online"
+		 * case.
+		 */
+		if (contains_standby_increment(start, start + size))
+			rc = -EPERM;
+		break;
+	case MEM_PREPARE_ONLINE:
+		/*
+		 * Access the altmap_start_pfn and altmap_nr_pages fields
+		 * within the struct memory_notify specifically when dealing
+		 * with only MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers.
+		 *
+		 * When altmap is in use, take the specified memory range
+		 * online, which includes the altmap.
+		 */
+		if (arg->altmap_nr_pages) {
+			start = PFN_PHYS(arg->altmap_start_pfn);
+			size += PFN_PHYS(arg->altmap_nr_pages);
+		}
+		rc = sclp_mem_change_state(start, size, 1);
+		if (rc || !arg->altmap_nr_pages)
+			break;
+		/*
+		 * Set CMMA state to nodat here, since the struct page memory
+		 * at the beginning of the memory block will not go through the
+		 * buddy allocator later.
+		 */
+		__arch_set_page_nodat((void *)__va(start), arg->altmap_nr_pages);
+		break;
+	case MEM_FINISH_OFFLINE:
+		/*
+		 * When altmap is in use, take the specified memory range
+		 * offline, which includes the altmap.
+		 */
+		if (arg->altmap_nr_pages) {
+			start = PFN_PHYS(arg->altmap_start_pfn);
+			size += PFN_PHYS(arg->altmap_nr_pages);
+		}
+		sclp_mem_change_state(start, size, 0);
+		break;
+	default:
+		break;
+	}
+	mutex_unlock(&sclp_mem_mutex);
+	return rc ? NOTIFY_BAD : NOTIFY_OK;
+}
+
+static struct notifier_block sclp_mem_nb = {
+	.notifier_call = sclp_mem_notifier,
+};
+
+static void __init align_to_block_size(unsigned long *start,
+				       unsigned long *size,
+				       unsigned long alignment)
+{
+	unsigned long start_align, size_align;
+
+	start_align = roundup(*start, alignment);
+	size_align = rounddown(*start + *size, alignment) - start_align;
+
+	pr_info("Standby memory at 0x%lx (%luM of %luM usable)\n",
+		*start, size_align >> 20, *size >> 20);
+	*start = start_align;
+	*size = size_align;
+}
+
+static void __init add_memory_merged(u16 rn)
+{
+	unsigned long start, size, addr, block_size;
+	static u16 first_rn, num;
+
+	if (rn && first_rn && (first_rn + num == rn)) {
+		num++;
+		return;
+	}
+	if (!first_rn)
+		goto skip_add;
+	start = rn2addr(first_rn);
+	size = (unsigned long)num * sclp.rzm;
+	if (start >= ident_map_size)
+		goto skip_add;
+	if (start + size > ident_map_size)
+		size = ident_map_size - start;
+	block_size = memory_block_size_bytes();
+	align_to_block_size(&start, &size, block_size);
+	if (!size)
+		goto skip_add;
+	for (addr = start; addr < start + size; addr += block_size) {
+		add_memory(0, addr, block_size,
+			   cpu_has_edat1() ?
+			   MHP_MEMMAP_ON_MEMORY | MHP_OFFLINE_INACCESSIBLE : MHP_NONE);
+	}
+skip_add:
+	first_rn = rn;
+	num = 1;
+}
+
+static void __init sclp_add_standby_memory(void)
+{
+	struct memory_increment *incr;
+
+	list_for_each_entry(incr, &sclp_mem_list, list) {
+		if (incr->standby)
+			add_memory_merged(incr->rn);
+	}
+	add_memory_merged(0);
+}
+
+static void __init insert_increment(u16 rn, int standby, int assigned)
+{
+	struct memory_increment *incr, *new_incr;
+	struct list_head *prev;
+	u16 last_rn;
+
+	new_incr = kzalloc(sizeof(*new_incr), GFP_KERNEL);
+	if (!new_incr)
+		return;
+	new_incr->rn = rn;
+	new_incr->standby = standby;
+	last_rn = 0;
+	prev = &sclp_mem_list;
+	list_for_each_entry(incr, &sclp_mem_list, list) {
+		if (assigned && incr->rn > rn)
+			break;
+		if (!assigned && incr->rn - last_rn > 1)
+			break;
+		last_rn = incr->rn;
+		prev = &incr->list;
+	}
+	if (!assigned)
+		new_incr->rn = last_rn + 1;
+	if (new_incr->rn > sclp.rnmax) {
+		kfree(new_incr);
+		return;
+	}
+	list_add(&new_incr->list, prev);
+}
+
+static int __init sclp_detect_standby_memory(void)
+{
+	struct read_storage_sccb *sccb;
+	int i, id, assigned, rc;
+
+	/* No standby memory in kdump mode */
+	if (oldmem_data.start)
+		return 0;
+	if ((sclp.facilities & 0xe00000000000UL) != 0xe00000000000UL)
+		return 0;
+	rc = -ENOMEM;
+	sccb = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
+	if (!sccb)
+		goto out;
+	assigned = 0;
+	for (id = 0; id <= sclp_max_storage_id; id++) {
+		memset(sccb, 0, PAGE_SIZE);
+		sccb->header.length = PAGE_SIZE;
+		rc = sclp_sync_request(SCLP_CMDW_READ_STORAGE_INFO | id << 8, sccb);
+		if (rc)
+			goto out;
+		switch (sccb->header.response_code) {
+		case 0x0010:
+			set_bit(id, sclp_storage_ids);
+			for (i = 0; i < sccb->assigned; i++) {
+				if (!sccb->entries[i])
+					continue;
+				assigned++;
+				insert_increment(sccb->entries[i] >> 16, 0, 1);
+			}
+			break;
+		case 0x0310:
+			break;
+		case 0x0410:
+			for (i = 0; i < sccb->assigned; i++) {
+				if (!sccb->entries[i])
+					continue;
+				assigned++;
+				insert_increment(sccb->entries[i] >> 16, 1, 1);
+			}
+			break;
+		default:
+			rc = -EIO;
+			break;
+		}
+		if (!rc)
+			sclp_max_storage_id = sccb->max_id;
+	}
+	if (rc || list_empty(&sclp_mem_list))
+		goto out;
+	for (i = 1; i <= sclp.rnmax - assigned; i++)
+		insert_increment(0, 1, 0);
+	rc = register_memory_notifier(&sclp_mem_nb);
+	if (rc)
+		goto out;
+	sclp_add_standby_memory();
+out:
+	free_page((unsigned long)sccb);
+	return rc;
+}
+__initcall(sclp_detect_standby_memory);