/*
   * Xen implementation for transcendent memory (tmem)
   *
   * Copyright (C) 2009-2011 Oracle Corp.  All rights reserved.
   * Author: Dan Magenheimer
   */
  
  #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/types.h>
  #include <linux/init.h>
  #include <linux/pagemap.h>
  #include <linux/cleancache.h>
  #include <linux/frontswap.h>
  
  #include <xen/xen.h>
  #include <xen/interface/xen.h>
  #include <asm/xen/hypercall.h>
  #include <asm/xen/page.h>
  #include <asm/xen/hypervisor.h>
  #include <xen/tmem.h>
  
  #ifndef CONFIG_XEN_TMEM_MODULE
  bool __read_mostly tmem_enabled = false;
  
  static int __init enable_tmem(char *s)
  {
  	tmem_enabled = true;
  	return 1;
  }
  __setup("tmem", enable_tmem);
  #endif
  
  #ifdef CONFIG_CLEANCACHE
  static bool cleancache __read_mostly = true;
  module_param(cleancache, bool, S_IRUGO);
  static bool selfballooning __read_mostly = true;
  module_param(selfballooning, bool, S_IRUGO);
  #endif /* CONFIG_CLEANCACHE */
  
  #ifdef CONFIG_FRONTSWAP
  static bool frontswap __read_mostly = true;
  module_param(frontswap, bool, S_IRUGO);
  #else /* CONFIG_FRONTSWAP */
  #define frontswap (0)
  #endif /* CONFIG_FRONTSWAP */
  
  #ifdef CONFIG_XEN_SELFBALLOONING
  static bool selfshrinking __read_mostly = true;
  module_param(selfshrinking, bool, S_IRUGO);
  #endif /* CONFIG_XEN_SELFBALLOONING */
  
  #define TMEM_CONTROL               0
  #define TMEM_NEW_POOL              1
  #define TMEM_DESTROY_POOL          2
  #define TMEM_NEW_PAGE              3
  #define TMEM_PUT_PAGE              4
  #define TMEM_GET_PAGE              5
  #define TMEM_FLUSH_PAGE            6
  #define TMEM_FLUSH_OBJECT          7
  #define TMEM_READ                  8
  #define TMEM_WRITE                 9
  #define TMEM_XCHG                 10
  
  /* Bits for HYPERVISOR_tmem_op(TMEM_NEW_POOL) */
  #define TMEM_POOL_PERSIST          1
  #define TMEM_POOL_SHARED           2
  #define TMEM_POOL_PAGESIZE_SHIFT   4
  #define TMEM_VERSION_SHIFT        24
  
  
  struct tmem_pool_uuid {
  	u64 uuid_lo;
  	u64 uuid_hi;
  };
  
  struct tmem_oid {
  	u64 oid[3];
  };
  
  #define TMEM_POOL_PRIVATE_UUID	{ 0, 0 }
  
  /* flags for tmem_ops.new_pool */
  #define TMEM_POOL_PERSIST          1
  #define TMEM_POOL_SHARED           2
  
  /* xen tmem foundation ops/hypercalls */
  
  static inline int xen_tmem_op(u32 tmem_cmd, u32 tmem_pool, struct tmem_oid oid,
  	u32 index, unsigned long gmfn, u32 tmem_offset, u32 pfn_offset, u32 len)
  {
  	struct tmem_op op;
  	int rc = 0;
  
  	op.cmd = tmem_cmd;
  	op.pool_id = tmem_pool;
  	op.u.gen.oid[0] = oid.oid[0];
  	op.u.gen.oid[1] = oid.oid[1];
  	op.u.gen.oid[2] = oid.oid[2];
  	op.u.gen.index = index;
  	op.u.gen.tmem_offset = tmem_offset;
  	op.u.gen.pfn_offset = pfn_offset;
  	op.u.gen.len = len;
  	set_xen_guest_handle(op.u.gen.gmfn, (void *)gmfn);
  	rc = HYPERVISOR_tmem_op(&op);
  	return rc;
  }
  
  static int xen_tmem_new_pool(struct tmem_pool_uuid uuid,
  				u32 flags, unsigned long pagesize)
  {
  	struct tmem_op op;
  	int rc = 0, pageshift;
  
  	for (pageshift = 0; pagesize != 1; pageshift++)
  		pagesize >>= 1;
  	flags |= (pageshift - 12) << TMEM_POOL_PAGESIZE_SHIFT;
  	flags |= TMEM_SPEC_VERSION << TMEM_VERSION_SHIFT;
  	op.cmd = TMEM_NEW_POOL;
  	op.u.new.uuid[0] = uuid.uuid_lo;
  	op.u.new.uuid[1] = uuid.uuid_hi;
  	op.u.new.flags = flags;
  	rc = HYPERVISOR_tmem_op(&op);
  	return rc;
  }
  
  /* xen generic tmem ops */
  
  static int xen_tmem_put_page(u32 pool_id, struct tmem_oid oid,
  			     u32 index, unsigned long pfn)
  {
  	unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
  
  	return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
  		gmfn, 0, 0, 0);
  }
  
  static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
  			     u32 index, unsigned long pfn)
  {
  	unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
  
  	return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
  		gmfn, 0, 0, 0);
  }
  
  static int xen_tmem_flush_page(u32 pool_id, struct tmem_oid oid, u32 index)
  {
  	return xen_tmem_op(TMEM_FLUSH_PAGE, pool_id, oid, index,
  		0, 0, 0, 0);
  }
  
  static int xen_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
  {
  	return xen_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0);
  }
  
  
  #ifdef CONFIG_CLEANCACHE
  static int xen_tmem_destroy_pool(u32 pool_id)
  {
  	struct tmem_oid oid = { { 0 } };
  
  	return xen_tmem_op(TMEM_DESTROY_POOL, pool_id, oid, 0, 0, 0, 0, 0);
  }
  
  /* cleancache ops */
  
  static void tmem_cleancache_put_page(int pool, struct cleancache_filekey key,
  				     pgoff_t index, struct page *page)
  {
  	u32 ind = (u32) index;
  	struct tmem_oid oid = *(struct tmem_oid *)&key;
  	unsigned long pfn = page_to_pfn(page);
  
  	if (pool < 0)
  		return;
  	if (ind != index)
  		return;
  	mb(); /* ensure page is quiescent; tmem may address it with an alias */
  	(void)xen_tmem_put_page((u32)pool, oid, ind, pfn);
  }
  
  static int tmem_cleancache_get_page(int pool, struct cleancache_filekey key,
  				    pgoff_t index, struct page *page)
  {
  	u32 ind = (u32) index;
  	struct tmem_oid oid = *(struct tmem_oid *)&key;
  	unsigned long pfn = page_to_pfn(page);
  	int ret;
  
  	/* translate return values to linux semantics */
  	if (pool < 0)
  		return -1;
  	if (ind != index)
  		return -1;
  	ret = xen_tmem_get_page((u32)pool, oid, ind, pfn);
  	if (ret == 1)
  		return 0;
  	else
  		return -1;
  }
  
  static void tmem_cleancache_flush_page(int pool, struct cleancache_filekey key,
  				       pgoff_t index)
  {
  	u32 ind = (u32) index;
  	struct tmem_oid oid = *(struct tmem_oid *)&key;
  
  	if (pool < 0)
  		return;
  	if (ind != index)
  		return;
  	(void)xen_tmem_flush_page((u32)pool, oid, ind);
  }
  
  static void tmem_cleancache_flush_inode(int pool, struct cleancache_filekey key)
  {
  	struct tmem_oid oid = *(struct tmem_oid *)&key;
  
  	if (pool < 0)
  		return;
  	(void)xen_tmem_flush_object((u32)pool, oid);
  }
  
  static void tmem_cleancache_flush_fs(int pool)
  {
  	if (pool < 0)
  		return;
  	(void)xen_tmem_destroy_pool((u32)pool);
  }
  
  static int tmem_cleancache_init_fs(size_t pagesize)
  {
  	struct tmem_pool_uuid uuid_private = TMEM_POOL_PRIVATE_UUID;
  
  	return xen_tmem_new_pool(uuid_private, 0, pagesize);
  }
  
  static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
  {
  	struct tmem_pool_uuid shared_uuid;
  
  	shared_uuid.uuid_lo = *(u64 *)uuid;
  	shared_uuid.uuid_hi = *(u64 *)(&uuid[8]);
  	return xen_tmem_new_pool(shared_uuid, TMEM_POOL_SHARED, pagesize);
  }
  
  static struct cleancache_ops tmem_cleancache_ops = {
  	.put_page = tmem_cleancache_put_page,
  	.get_page = tmem_cleancache_get_page,
  	.invalidate_page = tmem_cleancache_flush_page,
  	.invalidate_inode = tmem_cleancache_flush_inode,
  	.invalidate_fs = tmem_cleancache_flush_fs,
  	.init_shared_fs = tmem_cleancache_init_shared_fs,
  	.init_fs = tmem_cleancache_init_fs
  };
  #endif
  
  #ifdef CONFIG_FRONTSWAP
  /* frontswap tmem operations */
  
  /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
  static int tmem_frontswap_poolid;
  
  /*
   * Swizzling increases objects per swaptype, increasing tmem concurrency
   * for heavy swaploads.  Later, larger nr_cpus -> larger SWIZ_BITS
   */
  #define SWIZ_BITS		4
  #define SWIZ_MASK		((1 << SWIZ_BITS) - 1)
  #define _oswiz(_type, _ind)	((_type << SWIZ_BITS) | (_ind & SWIZ_MASK))
  #define iswiz(_ind)		(_ind >> SWIZ_BITS)
  
  static inline struct tmem_oid oswiz(unsigned type, u32 ind)
  {
  	struct tmem_oid oid = { .oid = { 0 } };
  	oid.oid[0] = _oswiz(type, ind);
  	return oid;
  }
  
  /* returns 0 if the page was successfully put into frontswap, -1 if not */
  static int tmem_frontswap_store(unsigned type, pgoff_t offset,
  				   struct page *page)
  {
  	u64 ind64 = (u64)offset;
  	u32 ind = (u32)offset;
  	unsigned long pfn = page_to_pfn(page);
  	int pool = tmem_frontswap_poolid;
  	int ret;
  
  	if (pool < 0)
  		return -1;
  	if (ind64 != ind)
  		return -1;
  	mb(); /* ensure page is quiescent; tmem may address it with an alias */
  	ret = xen_tmem_put_page(pool, oswiz(type, ind), iswiz(ind), pfn);
  	/* translate Xen tmem return values to linux semantics */
  	if (ret == 1)
  		return 0;
  	else
  		return -1;
  }
  
  /*
   * returns 0 if the page was successfully gotten from frontswap, -1 if
   * was not present (should never happen!)
   */
  static int tmem_frontswap_load(unsigned type, pgoff_t offset,
  				   struct page *page)
  {
  	u64 ind64 = (u64)offset;
  	u32 ind = (u32)offset;
  	unsigned long pfn = page_to_pfn(page);
  	int pool = tmem_frontswap_poolid;
  	int ret;
  
  	if (pool < 0)
  		return -1;
  	if (ind64 != ind)
  		return -1;
  	ret = xen_tmem_get_page(pool, oswiz(type, ind), iswiz(ind), pfn);
  	/* translate Xen tmem return values to linux semantics */
  	if (ret == 1)
  		return 0;
  	else
  		return -1;
  }
  
  /* flush a single page from frontswap */
  static void tmem_frontswap_flush_page(unsigned type, pgoff_t offset)
  {
  	u64 ind64 = (u64)offset;
  	u32 ind = (u32)offset;
  	int pool = tmem_frontswap_poolid;
  
  	if (pool < 0)
  		return;
  	if (ind64 != ind)
  		return;
  	(void) xen_tmem_flush_page(pool, oswiz(type, ind), iswiz(ind));
  }
  
  /* flush all pages from the passed swaptype */
  static void tmem_frontswap_flush_area(unsigned type)
  {
  	int pool = tmem_frontswap_poolid;
  	int ind;
  
  	if (pool < 0)
  		return;
  	for (ind = SWIZ_MASK; ind >= 0; ind--)
  		(void)xen_tmem_flush_object(pool, oswiz(type, ind));
  }
  
  static void tmem_frontswap_init(unsigned ignored)
  {
  	struct tmem_pool_uuid private = TMEM_POOL_PRIVATE_UUID;
  
  	/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
  	if (tmem_frontswap_poolid < 0)
  		tmem_frontswap_poolid =
  		    xen_tmem_new_pool(private, TMEM_POOL_PERSIST, PAGE_SIZE);
  }
  
  static struct frontswap_ops tmem_frontswap_ops = {
  	.store = tmem_frontswap_store,
  	.load = tmem_frontswap_load,
  	.invalidate_page = tmem_frontswap_flush_page,
  	.invalidate_area = tmem_frontswap_flush_area,
  	.init = tmem_frontswap_init
  };
  #endif
  
  static int xen_tmem_init(void)
  {
  	if (!xen_domain())
  		return 0;
  #ifdef CONFIG_FRONTSWAP
  	if (tmem_enabled && frontswap) {
  		char *s = "";
  		struct frontswap_ops *old_ops;
  
  		tmem_frontswap_poolid = -1;
  		old_ops = frontswap_register_ops(&tmem_frontswap_ops);
  		if (IS_ERR(old_ops) || old_ops) {
  			if (IS_ERR(old_ops))
  				return PTR_ERR(old_ops);
  			s = " (WARNING: frontswap_ops overridden)";
  		}
  		pr_info("frontswap enabled, RAM provided by Xen Transcendent Memory%s
  ",
  			s);
  	}
  #endif
  #ifdef CONFIG_CLEANCACHE
  	BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
  	if (tmem_enabled && cleancache) {
  		char *s = "";
  		struct cleancache_ops *old_ops =
  			cleancache_register_ops(&tmem_cleancache_ops);
  		if (old_ops)
  			s = " (WARNING: cleancache_ops overridden)";
  		pr_info("cleancache enabled, RAM provided by Xen Transcendent Memory%s
  ",
  			s);
  	}
  #endif
  #ifdef CONFIG_XEN_SELFBALLOONING
  	/*
  	 * There is no point of driving pages to the swap system if they
  	 * aren't going anywhere in tmem universe.
  	 */
  	if (!frontswap) {
  		selfshrinking = false;
  		selfballooning = false;
  	}
  	xen_selfballoon_init(selfballooning, selfshrinking);
  #endif
  	return 0;
  }
  
  module_init(xen_tmem_init)
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Dan Magenheimer <dan.magenheimer@oracle.com>");
  MODULE_DESCRIPTION("Shim to Xen transcendent memory");