drivers/misc/sgi-xp/xpc_partition.c - linux - Git at Google

 /*
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
  * (C) Copyright 2020 Hewlett Packard Enterprise Development LP
  * Copyright (c) 2004-2008 Silicon Graphics, Inc.  All Rights Reserved.
  */

 /*
  * Cross Partition Communication (XPC) partition support.
  *
  *	This is the part of XPC that detects the presence/absence of
  *	other partitions. It provides a heartbeat and monitors the
  *	heartbeats of other partitions.
  *
  */

 #include <linux/device.h>
 #include <linux/hardirq.h>
 #include <linux/slab.h>
 #include "xpc.h"
 #include <asm/uv/uv_hub.h>

 /* XPC is exiting flag */
 int xpc_exiting;

 /* this partition's reserved page pointers */
 struct xpc_rsvd_page *xpc_rsvd_page;
 static unsigned long *xpc_part_nasids;
 unsigned long *xpc_mach_nasids;

 static int xpc_nasid_mask_nbytes;	/* #of bytes in nasid mask */
 int xpc_nasid_mask_nlongs;	/* #of longs in nasid mask */

 struct xpc_partition *xpc_partitions;

 /*
  * Guarantee that the kmalloc'd memory is cacheline aligned.
  */
 void *
 xpc_kmalloc_cacheline_aligned(size_t size, gfp_t flags, void **base)
 {
 	/* see if kmalloc will give us cachline aligned memory by default */
 	*base = kmalloc(size, flags);
 	if (*base == NULL)
 		return NULL;

 	if ((u64)*base == L1_CACHE_ALIGN((u64)*base))
 		return *base;

 	kfree(*base);

 	/* nope, we'll have to do it ourselves */
 	*base = kmalloc(size + L1_CACHE_BYTES, flags);
 	if (*base == NULL)
 		return NULL;

 	return (void *)L1_CACHE_ALIGN((u64)*base);
 }

 /*
  * Given a nasid, get the physical address of the  partition's reserved page
  * for that nasid. This function returns 0 on any error.
  */
 static unsigned long
 xpc_get_rsvd_page_pa(int nasid)
 {
 	enum xp_retval ret;
 	u64 cookie = 0;
 	unsigned long rp_pa = nasid;	/* seed with nasid */
 	size_t len = 0;
 	size_t buf_len = 0;
 	void *buf = NULL;
 	void *buf_base = NULL;
 	enum xp_retval (*get_partition_rsvd_page_pa)
 		(void *, u64 *, unsigned long *, size_t *) =
 		xpc_arch_ops.get_partition_rsvd_page_pa;

 	while (1) {

 		/* !!! rp_pa will need to be _gpa on UV.
 		 * ??? So do we save it into the architecture specific parts
 		 * ??? of the xpc_partition structure? Do we rename this
 		 * ??? function or have two versions? Rename rp_pa for UV to
 		 * ??? rp_gpa?
 		 */
 		ret = get_partition_rsvd_page_pa(buf, &cookie, &rp_pa, &len);

 		dev_dbg(xpc_part, "SAL returned with ret=%d, cookie=0x%016lx, "
 			"address=0x%016lx, len=0x%016lx\n", ret,
 			(unsigned long)cookie, rp_pa, len);

 		if (ret != xpNeedMoreInfo)
 			break;

 		if (len > buf_len) {
 			kfree(buf_base);
 			buf_len = L1_CACHE_ALIGN(len);
 			buf = xpc_kmalloc_cacheline_aligned(buf_len, GFP_KERNEL,
 							    &buf_base);
 			if (buf_base == NULL) {
 				dev_err(xpc_part, "unable to kmalloc "
 					"len=0x%016lx\n", buf_len);
 				ret = xpNoMemory;
 				break;
 			}
 		}

 		ret = xp_remote_memcpy(xp_pa(buf), rp_pa, len);
 		if (ret != xpSuccess) {
 			dev_dbg(xpc_part, "xp_remote_memcpy failed %d\n", ret);
 			break;
 		}
 	}

 	kfree(buf_base);

 	if (ret != xpSuccess)
 		rp_pa = 0;

 	dev_dbg(xpc_part, "reserved page at phys address 0x%016lx\n", rp_pa);
 	return rp_pa;
 }

 /*
  * Fill the partition reserved page with the information needed by
  * other partitions to discover we are alive and establish initial
  * communications.
  */
 int
 xpc_setup_rsvd_page(void)
 {
 	int ret;
 	struct xpc_rsvd_page *rp;
 	unsigned long rp_pa;
 	unsigned long new_ts_jiffies;

 	/* get the local reserved page's address */

 	preempt_disable();
 	rp_pa = xpc_get_rsvd_page_pa(xp_cpu_to_nasid(smp_processor_id()));
 	preempt_enable();
 	if (rp_pa == 0) {
 		dev_err(xpc_part, "SAL failed to locate the reserved page\n");
 		return -ESRCH;
 	}
 	rp = (struct xpc_rsvd_page *)__va(xp_socket_pa(rp_pa));

 	if (rp->SAL_version < 3) {
 		/* SAL_versions < 3 had a SAL_partid defined as a u8 */
 		rp->SAL_partid &= 0xff;
 	}
 	BUG_ON(rp->SAL_partid != xp_partition_id);

 	if (rp->SAL_partid < 0 || rp->SAL_partid >= xp_max_npartitions) {
 		dev_err(xpc_part, "the reserved page's partid of %d is outside "
 			"supported range (< 0 || >= %d)\n", rp->SAL_partid,
 			xp_max_npartitions);
 		return -EINVAL;
 	}

 	rp->version = XPC_RP_VERSION;
 	rp->max_npartitions = xp_max_npartitions;

 	/* establish the actual sizes of the nasid masks */
 	if (rp->SAL_version == 1) {
 		/* SAL_version 1 didn't set the nasids_size field */
 		rp->SAL_nasids_size = 128;
 	}
 	xpc_nasid_mask_nbytes = rp->SAL_nasids_size;
 	xpc_nasid_mask_nlongs = BITS_TO_LONGS(rp->SAL_nasids_size *
 					      BITS_PER_BYTE);

 	/* setup the pointers to the various items in the reserved page */
 	xpc_part_nasids = XPC_RP_PART_NASIDS(rp);
 	xpc_mach_nasids = XPC_RP_MACH_NASIDS(rp);

 	ret = xpc_arch_ops.setup_rsvd_page(rp);
 	if (ret != 0)
 		return ret;

 	/*
 	 * Set timestamp of when reserved page was setup by XPC.
 	 * This signifies to the remote partition that our reserved
 	 * page is initialized.
 	 */
 	new_ts_jiffies = jiffies;
 	if (new_ts_jiffies == 0 || new_ts_jiffies == rp->ts_jiffies)
 		new_ts_jiffies++;
 	rp->ts_jiffies = new_ts_jiffies;

 	xpc_rsvd_page = rp;
 	return 0;
 }

 void
 xpc_teardown_rsvd_page(void)
 {
 	/* a zero timestamp indicates our rsvd page is not initialized */
 	xpc_rsvd_page->ts_jiffies = 0;
 }

 /*
  * Get a copy of a portion of the remote partition's rsvd page.
  *
  * remote_rp points to a buffer that is cacheline aligned for BTE copies and
  * is large enough to contain a copy of their reserved page header and
  * part_nasids mask.
  */
 enum xp_retval
 xpc_get_remote_rp(int nasid, unsigned long *discovered_nasids,
 		  struct xpc_rsvd_page *remote_rp, unsigned long *remote_rp_pa)
 {
 	int l;
 	enum xp_retval ret;

 	/* get the reserved page's physical address */

 	*remote_rp_pa = xpc_get_rsvd_page_pa(nasid);
 	if (*remote_rp_pa == 0)
 		return xpNoRsvdPageAddr;

 	/* pull over the reserved page header and part_nasids mask */
 	ret = xp_remote_memcpy(xp_pa(remote_rp), *remote_rp_pa,
 			       XPC_RP_HEADER_SIZE + xpc_nasid_mask_nbytes);
 	if (ret != xpSuccess)
 		return ret;

 	if (discovered_nasids != NULL) {
 		unsigned long *remote_part_nasids =
 		    XPC_RP_PART_NASIDS(remote_rp);

 		for (l = 0; l < xpc_nasid_mask_nlongs; l++)
 			discovered_nasids[l] |= remote_part_nasids[l];
 	}

 	/* zero timestamp indicates the reserved page has not been setup */
 	if (remote_rp->ts_jiffies == 0)
 		return xpRsvdPageNotSet;

 	if (XPC_VERSION_MAJOR(remote_rp->version) !=
 	    XPC_VERSION_MAJOR(XPC_RP_VERSION)) {
 		return xpBadVersion;
 	}

 	/* check that both remote and local partids are valid for each side */
 	if (remote_rp->SAL_partid < 0 ||
 	    remote_rp->SAL_partid >= xp_max_npartitions ||
 	    remote_rp->max_npartitions <= xp_partition_id) {
 		return xpInvalidPartid;
 	}

 	if (remote_rp->SAL_partid == xp_partition_id)
 		return xpLocalPartid;

 	return xpSuccess;
 }

 /*
  * See if the other side has responded to a partition deactivate request
  * from us. Though we requested the remote partition to deactivate with regard
  * to us, we really only need to wait for the other side to disengage from us.
  */
 static int __xpc_partition_disengaged(struct xpc_partition *part,
 				      bool from_timer)
 {
 	short partid = XPC_PARTID(part);
 	int disengaged;

 	disengaged = !xpc_arch_ops.partition_engaged(partid);
 	if (part->disengage_timeout) {
 		if (!disengaged) {
 			if (time_is_after_jiffies(part->disengage_timeout)) {
 				/* timelimit hasn't been reached yet */
 				return 0;
 			}

 			/*
 			 * Other side hasn't responded to our deactivate
 			 * request in a timely fashion, so assume it's dead.
 			 */

 			dev_info(xpc_part, "deactivate request to remote "
 				 "partition %d timed out\n", partid);
 			xpc_disengage_timedout = 1;
 			xpc_arch_ops.assume_partition_disengaged(partid);
 			disengaged = 1;
 		}
 		part->disengage_timeout = 0;

 		/* Cancel the timer function if not called from it */
 		if (!from_timer)
 			del_timer_sync(&part->disengage_timer);

 		DBUG_ON(part->act_state != XPC_P_AS_DEACTIVATING &&
 			part->act_state != XPC_P_AS_INACTIVE);
 		if (part->act_state != XPC_P_AS_INACTIVE)
 			xpc_wakeup_channel_mgr(part);

 		xpc_arch_ops.cancel_partition_deactivation_request(part);
 	}
 	return disengaged;
 }

 int xpc_partition_disengaged(struct xpc_partition *part)
 {
 	return __xpc_partition_disengaged(part, false);
 }

 int xpc_partition_disengaged_from_timer(struct xpc_partition *part)
 {
 	return __xpc_partition_disengaged(part, true);
 }

 /*
  * Mark specified partition as active.
  */
 enum xp_retval
 xpc_mark_partition_active(struct xpc_partition *part)
 {
 	unsigned long irq_flags;
 	enum xp_retval ret;

 	dev_dbg(xpc_part, "setting partition %d to ACTIVE\n", XPC_PARTID(part));

 	spin_lock_irqsave(&part->act_lock, irq_flags);
 	if (part->act_state == XPC_P_AS_ACTIVATING) {
 		part->act_state = XPC_P_AS_ACTIVE;
 		ret = xpSuccess;
 	} else {
 		DBUG_ON(part->reason == xpSuccess);
 		ret = part->reason;
 	}
 	spin_unlock_irqrestore(&part->act_lock, irq_flags);

 	return ret;
 }

 /*
  * Start the process of deactivating the specified partition.
  */
 void
 xpc_deactivate_partition(const int line, struct xpc_partition *part,
 			 enum xp_retval reason)
 {
 	unsigned long irq_flags;

 	spin_lock_irqsave(&part->act_lock, irq_flags);

 	if (part->act_state == XPC_P_AS_INACTIVE) {
 		XPC_SET_REASON(part, reason, line);
 		spin_unlock_irqrestore(&part->act_lock, irq_flags);
 		if (reason == xpReactivating) {
 			/* we interrupt ourselves to reactivate partition */
 			xpc_arch_ops.request_partition_reactivation(part);
 		}
 		return;
 	}
 	if (part->act_state == XPC_P_AS_DEACTIVATING) {
 		if ((part->reason == xpUnloading && reason != xpUnloading) ||
 		    reason == xpReactivating) {
 			XPC_SET_REASON(part, reason, line);
 		}
 		spin_unlock_irqrestore(&part->act_lock, irq_flags);
 		return;
 	}

 	part->act_state = XPC_P_AS_DEACTIVATING;
 	XPC_SET_REASON(part, reason, line);

 	spin_unlock_irqrestore(&part->act_lock, irq_flags);

 	/* ask remote partition to deactivate with regard to us */
 	xpc_arch_ops.request_partition_deactivation(part);

 	/* set a timelimit on the disengage phase of the deactivation request */
 	part->disengage_timeout = jiffies + (xpc_disengage_timelimit * HZ);
 	part->disengage_timer.expires = part->disengage_timeout;
 	add_timer(&part->disengage_timer);

 	dev_dbg(xpc_part, "bringing partition %d down, reason = %d\n",
 		XPC_PARTID(part), reason);

 	xpc_partition_going_down(part, reason);
 }

 /*
  * Mark specified partition as inactive.
  */
 void
 xpc_mark_partition_inactive(struct xpc_partition *part)
 {
 	unsigned long irq_flags;

 	dev_dbg(xpc_part, "setting partition %d to INACTIVE\n",
 		XPC_PARTID(part));

 	spin_lock_irqsave(&part->act_lock, irq_flags);
 	part->act_state = XPC_P_AS_INACTIVE;
 	spin_unlock_irqrestore(&part->act_lock, irq_flags);
 	part->remote_rp_pa = 0;
 }

 /*
  * SAL has provided a partition and machine mask.  The partition mask
  * contains a bit for each even nasid in our partition.  The machine
  * mask contains a bit for each even nasid in the entire machine.
  *
  * Using those two bit arrays, we can determine which nasids are
  * known in the machine.  Each should also have a reserved page
  * initialized if they are available for partitioning.
  */
 void
 xpc_discovery(void)
 {
 	void *remote_rp_base;
 	struct xpc_rsvd_page *remote_rp;
 	unsigned long remote_rp_pa;
 	int region;
 	int region_size;
 	int max_regions;
 	int nasid;
 	unsigned long *discovered_nasids;
 	enum xp_retval ret;

 	remote_rp = xpc_kmalloc_cacheline_aligned(XPC_RP_HEADER_SIZE +
 						  xpc_nasid_mask_nbytes,
 						  GFP_KERNEL, &remote_rp_base);
 	if (remote_rp == NULL)
 		return;

 	discovered_nasids = kcalloc(xpc_nasid_mask_nlongs, sizeof(long),
 				    GFP_KERNEL);
 	if (discovered_nasids == NULL) {
 		kfree(remote_rp_base);
 		return;
 	}

 	/*
 	 * The term 'region' in this context refers to the minimum number of
 	 * nodes that can comprise an access protection grouping. The access
 	 * protection is in regards to memory, IOI and IPI.
 	 */
 	region_size = xp_region_size;

 	if (is_uv_system())
 		max_regions = 256;
 	else {
 		max_regions = 64;

 		switch (region_size) {
 		case 128:
 			max_regions *= 2;
 			fallthrough;
 		case 64:
 			max_regions *= 2;
 			fallthrough;
 		case 32:
 			max_regions *= 2;
 			region_size = 16;
 		}
 	}

 	for (region = 0; region < max_regions; region++) {

 		if (xpc_exiting)
 			break;

 		dev_dbg(xpc_part, "searching region %d\n", region);

 		for (nasid = (region * region_size * 2);
 		     nasid < ((region + 1) * region_size * 2); nasid += 2) {

 			if (xpc_exiting)
 				break;

 			dev_dbg(xpc_part, "checking nasid %d\n", nasid);

 			if (test_bit(nasid / 2, xpc_part_nasids)) {
 				dev_dbg(xpc_part, "PROM indicates Nasid %d is "
 					"part of the local partition; skipping "
 					"region\n", nasid);
 				break;
 			}

 			if (!(test_bit(nasid / 2, xpc_mach_nasids))) {
 				dev_dbg(xpc_part, "PROM indicates Nasid %d was "
 					"not on Numa-Link network at reset\n",
 					nasid);
 				continue;
 			}

 			if (test_bit(nasid / 2, discovered_nasids)) {
 				dev_dbg(xpc_part, "Nasid %d is part of a "
 					"partition which was previously "
 					"discovered\n", nasid);
 				continue;
 			}

 			/* pull over the rsvd page header & part_nasids mask */

 			ret = xpc_get_remote_rp(nasid, discovered_nasids,
 						remote_rp, &remote_rp_pa);
 			if (ret != xpSuccess) {
 				dev_dbg(xpc_part, "unable to get reserved page "
 					"from nasid %d, reason=%d\n", nasid,
 					ret);

 				if (ret == xpLocalPartid)
 					break;

 				continue;
 			}

 			xpc_arch_ops.request_partition_activation(remote_rp,
 							 remote_rp_pa, nasid);
 		}
 	}

 	kfree(discovered_nasids);
 	kfree(remote_rp_base);
 }

 /*
  * Given a partid, get the nasids owned by that partition from the
  * remote partition's reserved page.
  */
 enum xp_retval
 xpc_initiate_partid_to_nasids(short partid, void *nasid_mask)
 {
 	struct xpc_partition *part;
 	unsigned long part_nasid_pa;

 	part = &xpc_partitions[partid];
 	if (part->remote_rp_pa == 0)
 		return xpPartitionDown;

 	memset(nasid_mask, 0, xpc_nasid_mask_nbytes);

 	part_nasid_pa = (unsigned long)XPC_RP_PART_NASIDS(part->remote_rp_pa);

 	return xp_remote_memcpy(xp_pa(nasid_mask), part_nasid_pa,
 				xpc_nasid_mask_nbytes);
 }
	/*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*
	* (C) Copyright 2020 Hewlett Packard Enterprise Development LP
	* Copyright (c) 2004-2008 Silicon Graphics, Inc. All Rights Reserved.
	*/

	/*
	* Cross Partition Communication (XPC) partition support.
	*
	* This is the part of XPC that detects the presence/absence of
	* other partitions. It provides a heartbeat and monitors the
	* heartbeats of other partitions.
	*
	*/

	#include <linux/device.h>
	#include <linux/hardirq.h>
	#include <linux/slab.h>
	#include "xpc.h"
	#include <asm/uv/uv_hub.h>

	/* XPC is exiting flag */
	int xpc_exiting;

	/* this partition's reserved page pointers */
	struct xpc_rsvd_page *xpc_rsvd_page;
	static unsigned long *xpc_part_nasids;
	unsigned long *xpc_mach_nasids;

	static int xpc_nasid_mask_nbytes; /* #of bytes in nasid mask */
	int xpc_nasid_mask_nlongs; /* #of longs in nasid mask */

	struct xpc_partition *xpc_partitions;

	/*
	* Guarantee that the kmalloc'd memory is cacheline aligned.
	*/
	void *
	xpc_kmalloc_cacheline_aligned(size_t size, gfp_t flags, void **base)
	{
	/* see if kmalloc will give us cachline aligned memory by default */
	*base = kmalloc(size, flags);
	if (*base == NULL)
	return NULL;

	if ((u64)base == L1_CACHE_ALIGN((u64)base))
	return *base;

	kfree(*base);

	/* nope, we'll have to do it ourselves */
	*base = kmalloc(size + L1_CACHE_BYTES, flags);
	if (*base == NULL)
	return NULL;

	return (void )L1_CACHE_ALIGN((u64)base);
	}

	/*
	* Given a nasid, get the physical address of the partition's reserved page
	* for that nasid. This function returns 0 on any error.
	*/
	static unsigned long
	xpc_get_rsvd_page_pa(int nasid)
	{
	enum xp_retval ret;
	u64 cookie = 0;
	unsigned long rp_pa = nasid; /* seed with nasid */
	size_t len = 0;
	size_t buf_len = 0;
	void *buf = NULL;
	void *buf_base = NULL;
	enum xp_retval (*get_partition_rsvd_page_pa)
	(void , u64 , unsigned long , size_t ) =
	xpc_arch_ops.get_partition_rsvd_page_pa;

	while (1) {

	/* !!! rp_pa will need to be _gpa on UV.
	* ??? So do we save it into the architecture specific parts
	* ??? of the xpc_partition structure? Do we rename this
	* ??? function or have two versions? Rename rp_pa for UV to
	* ??? rp_gpa?
	*/
	ret = get_partition_rsvd_page_pa(buf, &cookie, &rp_pa, &len);

	dev_dbg(xpc_part, "SAL returned with ret=%d, cookie=0x%016lx, "
	"address=0x%016lx, len=0x%016lx\n", ret,
	(unsigned long)cookie, rp_pa, len);

	if (ret != xpNeedMoreInfo)
	break;

	if (len > buf_len) {
	kfree(buf_base);
	buf_len = L1_CACHE_ALIGN(len);
	buf = xpc_kmalloc_cacheline_aligned(buf_len, GFP_KERNEL,
	&buf_base);
	if (buf_base == NULL) {
	dev_err(xpc_part, "unable to kmalloc "
	"len=0x%016lx\n", buf_len);
	ret = xpNoMemory;
	break;
	}
	}

	ret = xp_remote_memcpy(xp_pa(buf), rp_pa, len);
	if (ret != xpSuccess) {
	dev_dbg(xpc_part, "xp_remote_memcpy failed %d\n", ret);
	break;
	}
	}

	kfree(buf_base);

	if (ret != xpSuccess)
	rp_pa = 0;

	dev_dbg(xpc_part, "reserved page at phys address 0x%016lx\n", rp_pa);
	return rp_pa;
	}

	/*
	* Fill the partition reserved page with the information needed by
	* other partitions to discover we are alive and establish initial
	* communications.
	*/
	int
	xpc_setup_rsvd_page(void)
	{
	int ret;
	struct xpc_rsvd_page *rp;
	unsigned long rp_pa;
	unsigned long new_ts_jiffies;

	/* get the local reserved page's address */

	preempt_disable();
	rp_pa = xpc_get_rsvd_page_pa(xp_cpu_to_nasid(smp_processor_id()));
	preempt_enable();
	if (rp_pa == 0) {
	dev_err(xpc_part, "SAL failed to locate the reserved page\n");
	return -ESRCH;
	}
	rp = (struct xpc_rsvd_page *)__va(xp_socket_pa(rp_pa));

	if (rp->SAL_version < 3) {
	/* SAL_versions < 3 had a SAL_partid defined as a u8 */
	rp->SAL_partid &= 0xff;
	}
	BUG_ON(rp->SAL_partid != xp_partition_id);

	if (rp->SAL_partid < 0 \|\| rp->SAL_partid >= xp_max_npartitions) {
	dev_err(xpc_part, "the reserved page's partid of %d is outside "
	"supported range (< 0 \|\| >= %d)\n", rp->SAL_partid,
	xp_max_npartitions);
	return -EINVAL;
	}

	rp->version = XPC_RP_VERSION;
	rp->max_npartitions = xp_max_npartitions;

	/* establish the actual sizes of the nasid masks */
	if (rp->SAL_version == 1) {
	/* SAL_version 1 didn't set the nasids_size field */
	rp->SAL_nasids_size = 128;
	}
	xpc_nasid_mask_nbytes = rp->SAL_nasids_size;
	xpc_nasid_mask_nlongs = BITS_TO_LONGS(rp->SAL_nasids_size *
	BITS_PER_BYTE);

	/* setup the pointers to the various items in the reserved page */
	xpc_part_nasids = XPC_RP_PART_NASIDS(rp);
	xpc_mach_nasids = XPC_RP_MACH_NASIDS(rp);

	ret = xpc_arch_ops.setup_rsvd_page(rp);
	if (ret != 0)
	return ret;

	/*
	* Set timestamp of when reserved page was setup by XPC.
	* This signifies to the remote partition that our reserved
	* page is initialized.
	*/
	new_ts_jiffies = jiffies;
	if (new_ts_jiffies == 0 \|\| new_ts_jiffies == rp->ts_jiffies)
	new_ts_jiffies++;
	rp->ts_jiffies = new_ts_jiffies;

	xpc_rsvd_page = rp;
	return 0;
	}

	void
	xpc_teardown_rsvd_page(void)
	{
	/* a zero timestamp indicates our rsvd page is not initialized */
	xpc_rsvd_page->ts_jiffies = 0;
	}

	/*
	* Get a copy of a portion of the remote partition's rsvd page.
	*
	* remote_rp points to a buffer that is cacheline aligned for BTE copies and
	* is large enough to contain a copy of their reserved page header and
	* part_nasids mask.
	*/
	enum xp_retval
	xpc_get_remote_rp(int nasid, unsigned long *discovered_nasids,
	struct xpc_rsvd_page remote_rp, unsigned long remote_rp_pa)
	{
	int l;
	enum xp_retval ret;

	/* get the reserved page's physical address */

	*remote_rp_pa = xpc_get_rsvd_page_pa(nasid);
	if (*remote_rp_pa == 0)
	return xpNoRsvdPageAddr;

	/* pull over the reserved page header and part_nasids mask */
	ret = xp_remote_memcpy(xp_pa(remote_rp), *remote_rp_pa,
	XPC_RP_HEADER_SIZE + xpc_nasid_mask_nbytes);
	if (ret != xpSuccess)
	return ret;

	if (discovered_nasids != NULL) {
	unsigned long *remote_part_nasids =
	XPC_RP_PART_NASIDS(remote_rp);

	for (l = 0; l < xpc_nasid_mask_nlongs; l++)
	discovered_nasids[l] \|= remote_part_nasids[l];
	}

	/* zero timestamp indicates the reserved page has not been setup */
	if (remote_rp->ts_jiffies == 0)
	return xpRsvdPageNotSet;

	if (XPC_VERSION_MAJOR(remote_rp->version) !=
	XPC_VERSION_MAJOR(XPC_RP_VERSION)) {
	return xpBadVersion;
	}

	/* check that both remote and local partids are valid for each side */
	if (remote_rp->SAL_partid < 0 \|\|
	remote_rp->SAL_partid >= xp_max_npartitions \|\|
	remote_rp->max_npartitions <= xp_partition_id) {
	return xpInvalidPartid;
	}

	if (remote_rp->SAL_partid == xp_partition_id)
	return xpLocalPartid;

	return xpSuccess;
	}

	/*
	* See if the other side has responded to a partition deactivate request
	* from us. Though we requested the remote partition to deactivate with regard
	* to us, we really only need to wait for the other side to disengage from us.
	*/
	static int __xpc_partition_disengaged(struct xpc_partition *part,
	bool from_timer)
	{
	short partid = XPC_PARTID(part);
	int disengaged;

	disengaged = !xpc_arch_ops.partition_engaged(partid);
	if (part->disengage_timeout) {
	if (!disengaged) {
	if (time_is_after_jiffies(part->disengage_timeout)) {
	/* timelimit hasn't been reached yet */
	return 0;
	}

	/*
	* Other side hasn't responded to our deactivate
	* request in a timely fashion, so assume it's dead.
	*/

	dev_info(xpc_part, "deactivate request to remote "
	"partition %d timed out\n", partid);
	xpc_disengage_timedout = 1;
	xpc_arch_ops.assume_partition_disengaged(partid);
	disengaged = 1;
	}
	part->disengage_timeout = 0;

	/* Cancel the timer function if not called from it */
	if (!from_timer)
	del_timer_sync(&part->disengage_timer);

	DBUG_ON(part->act_state != XPC_P_AS_DEACTIVATING &&
	part->act_state != XPC_P_AS_INACTIVE);
	if (part->act_state != XPC_P_AS_INACTIVE)
	xpc_wakeup_channel_mgr(part);

	xpc_arch_ops.cancel_partition_deactivation_request(part);
	}
	return disengaged;
	}

	int xpc_partition_disengaged(struct xpc_partition *part)
	{
	return __xpc_partition_disengaged(part, false);
	}

	int xpc_partition_disengaged_from_timer(struct xpc_partition *part)
	{
	return __xpc_partition_disengaged(part, true);
	}

	/*
	* Mark specified partition as active.
	*/
	enum xp_retval
	xpc_mark_partition_active(struct xpc_partition *part)
	{
	unsigned long irq_flags;
	enum xp_retval ret;

	dev_dbg(xpc_part, "setting partition %d to ACTIVE\n", XPC_PARTID(part));

	spin_lock_irqsave(&part->act_lock, irq_flags);
	if (part->act_state == XPC_P_AS_ACTIVATING) {
	part->act_state = XPC_P_AS_ACTIVE;
	ret = xpSuccess;
	} else {
	DBUG_ON(part->reason == xpSuccess);
	ret = part->reason;
	}
	spin_unlock_irqrestore(&part->act_lock, irq_flags);

	return ret;
	}

	/*
	* Start the process of deactivating the specified partition.
	*/
	void
	xpc_deactivate_partition(const int line, struct xpc_partition *part,
	enum xp_retval reason)
	{
	unsigned long irq_flags;

	spin_lock_irqsave(&part->act_lock, irq_flags);

	if (part->act_state == XPC_P_AS_INACTIVE) {
	XPC_SET_REASON(part, reason, line);
	spin_unlock_irqrestore(&part->act_lock, irq_flags);
	if (reason == xpReactivating) {
	/* we interrupt ourselves to reactivate partition */
	xpc_arch_ops.request_partition_reactivation(part);
	}
	return;
	}
	if (part->act_state == XPC_P_AS_DEACTIVATING) {
	if ((part->reason == xpUnloading && reason != xpUnloading) \|\|
	reason == xpReactivating) {
	XPC_SET_REASON(part, reason, line);
	}
	spin_unlock_irqrestore(&part->act_lock, irq_flags);
	return;
	}

	part->act_state = XPC_P_AS_DEACTIVATING;
	XPC_SET_REASON(part, reason, line);

	spin_unlock_irqrestore(&part->act_lock, irq_flags);

	/* ask remote partition to deactivate with regard to us */
	xpc_arch_ops.request_partition_deactivation(part);

	/* set a timelimit on the disengage phase of the deactivation request */
	part->disengage_timeout = jiffies + (xpc_disengage_timelimit * HZ);
	part->disengage_timer.expires = part->disengage_timeout;
	add_timer(&part->disengage_timer);

	dev_dbg(xpc_part, "bringing partition %d down, reason = %d\n",
	XPC_PARTID(part), reason);

	xpc_partition_going_down(part, reason);
	}

	/*
	* Mark specified partition as inactive.
	*/
	void
	xpc_mark_partition_inactive(struct xpc_partition *part)
	{
	unsigned long irq_flags;

	dev_dbg(xpc_part, "setting partition %d to INACTIVE\n",
	XPC_PARTID(part));

	spin_lock_irqsave(&part->act_lock, irq_flags);
	part->act_state = XPC_P_AS_INACTIVE;
	spin_unlock_irqrestore(&part->act_lock, irq_flags);
	part->remote_rp_pa = 0;
	}

	/*
	* SAL has provided a partition and machine mask. The partition mask
	* contains a bit for each even nasid in our partition. The machine
	* mask contains a bit for each even nasid in the entire machine.
	*
	* Using those two bit arrays, we can determine which nasids are
	* known in the machine. Each should also have a reserved page
	* initialized if they are available for partitioning.
	*/
	void
	xpc_discovery(void)
	{
	void *remote_rp_base;
	struct xpc_rsvd_page *remote_rp;
	unsigned long remote_rp_pa;
	int region;
	int region_size;
	int max_regions;
	int nasid;
	unsigned long *discovered_nasids;
	enum xp_retval ret;

	remote_rp = xpc_kmalloc_cacheline_aligned(XPC_RP_HEADER_SIZE +
	xpc_nasid_mask_nbytes,
	GFP_KERNEL, &remote_rp_base);
	if (remote_rp == NULL)
	return;

	discovered_nasids = kcalloc(xpc_nasid_mask_nlongs, sizeof(long),
	GFP_KERNEL);
	if (discovered_nasids == NULL) {
	kfree(remote_rp_base);
	return;
	}

	/*
	* The term 'region' in this context refers to the minimum number of
	* nodes that can comprise an access protection grouping. The access
	* protection is in regards to memory, IOI and IPI.
	*/
	region_size = xp_region_size;

	if (is_uv_system())
	max_regions = 256;
	else {
	max_regions = 64;

	switch (region_size) {
	case 128:
	max_regions *= 2;
	fallthrough;
	case 64:
	max_regions *= 2;
	fallthrough;
	case 32:
	max_regions *= 2;
	region_size = 16;
	}
	}

	for (region = 0; region < max_regions; region++) {

	if (xpc_exiting)
	break;

	dev_dbg(xpc_part, "searching region %d\n", region);

	for (nasid = (region * region_size * 2);
	nasid < ((region + 1) * region_size * 2); nasid += 2) {

	if (xpc_exiting)
	break;

	dev_dbg(xpc_part, "checking nasid %d\n", nasid);

	if (test_bit(nasid / 2, xpc_part_nasids)) {
	dev_dbg(xpc_part, "PROM indicates Nasid %d is "
	"part of the local partition; skipping "
	"region\n", nasid);
	break;
	}

	if (!(test_bit(nasid / 2, xpc_mach_nasids))) {
	dev_dbg(xpc_part, "PROM indicates Nasid %d was "
	"not on Numa-Link network at reset\n",
	nasid);
	continue;
	}

	if (test_bit(nasid / 2, discovered_nasids)) {
	dev_dbg(xpc_part, "Nasid %d is part of a "
	"partition which was previously "
	"discovered\n", nasid);
	continue;
	}

	/* pull over the rsvd page header & part_nasids mask */

	ret = xpc_get_remote_rp(nasid, discovered_nasids,
	remote_rp, &remote_rp_pa);
	if (ret != xpSuccess) {
	dev_dbg(xpc_part, "unable to get reserved page "
	"from nasid %d, reason=%d\n", nasid,
	ret);

	if (ret == xpLocalPartid)
	break;

	continue;
	}

	xpc_arch_ops.request_partition_activation(remote_rp,
	remote_rp_pa, nasid);
	}
	}

	kfree(discovered_nasids);
	kfree(remote_rp_base);
	}

	/*
	* Given a partid, get the nasids owned by that partition from the
	* remote partition's reserved page.
	*/
	enum xp_retval
	xpc_initiate_partid_to_nasids(short partid, void *nasid_mask)
	{
	struct xpc_partition *part;
	unsigned long part_nasid_pa;

	part = &xpc_partitions[partid];
	if (part->remote_rp_pa == 0)
	return xpPartitionDown;

	memset(nasid_mask, 0, xpc_nasid_mask_nbytes);

	part_nasid_pa = (unsigned long)XPC_RP_PART_NASIDS(part->remote_rp_pa);

	return xp_remote_memcpy(xp_pa(nasid_mask), part_nasid_pa,
	xpc_nasid_mask_nbytes);
	}