// 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);