[Patch 2/2] Special Memory (mspec) driver.

[Robin Holt]

Introduce the special memory (mspec) driver.  This is used to allow
userland to map fetchop, etc pages

Signed-off-by: holt@xxxxxxx



Index: linux-2.6/arch/ia64/Kconfig
===================================================================
--- linux-2.6.orig/arch/ia64/Kconfig	2005-10-12 10:56:32.557090935 -0500
+++ linux-2.6/arch/ia64/Kconfig	2005-10-12 11:01:48.514666806 -0500
@@ -231,6 +231,16 @@ config IA64_SGI_SN_XP
 	  this feature will allow for direct communication between SSIs
 	  based on a network adapter and DMA messaging.
 
+config MSPEC
+	tristate "Special Memory support"
+	select IA64_UNCACHED_ALLOCATOR
+	help
+	  This driver allows for cached and uncached mappings of memory
+	  to user processes. On SGI SN hardware it will also export the
+	  special fetchop memory facility.
+	  Fetchops are atomic memory operations that are implemented in the
+	  memory controller on SGI SN hardware.
+
 config FORCE_MAX_ZONEORDER
 	int
 	default "18"
Index: linux-2.6/arch/ia64/kernel/Makefile
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/Makefile	2005-10-12 10:56:32.558067400 -0500
+++ linux-2.6/arch/ia64/kernel/Makefile	2005-10-12 11:01:48.520525594 -0500
@@ -23,6 +23,7 @@ obj-$(CONFIG_IA64_CYCLONE)	+= cyclone.o
 obj-$(CONFIG_CPU_FREQ)		+= cpufreq/
 obj-$(CONFIG_IA64_MCA_RECOVERY)	+= mca_recovery.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o jprobes.o
+obj-$(CONFIG_MSPEC)		+= mspec.o
 obj-$(CONFIG_IA64_UNCACHED_ALLOCATOR)	+= uncached.o
 mca_recovery-y			+= mca_drv.o mca_drv_asm.o
 
Index: linux-2.6/arch/ia64/kernel/mspec.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/arch/ia64/kernel/mspec.c	2005-10-12 11:02:50.347333000 -0500
@@ -0,0 +1,498 @@
+/*
+ * Copyright (C) 2001-2005 Silicon Graphics, Inc.  All rights
+ * reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ */
+
+/*
+ * SN Platform Special Memory (mspec) Support
+ *
+ * This driver exports the SN special memory (mspec) facility to user processes.
+ * There are three types of memory made available thru this driver:
+ * fetchops, uncached and cached.
+ *
+ * Fetchops are atomic memory operations that are implemented in the
+ * memory controller on SGI SN hardware.
+ *
+ * Uncached are used for memory write combining feature of the ia64
+ * cpu.
+ *
+ * Cached are used for areas of memory that are used as cached addresses
+ * on our partition and used as uncached addresses from other partitions.
+ * Due to a design constraint of the SN2 Shub, you can not have processors
+ * on the same FSB perform both a cached and uncached reference to the
+ * same cache line.  These special memory cached regions prevent the
+ * kernel from ever dropping in a TLB entry and therefore prevent the
+ * processor from ever speculating a cache line from this page.
+ */
+
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/miscdevice.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/vmalloc.h>
+#include <linux/bitops.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/seq_file.h>
+#include <linux/efi.h>
+#include <asm/page.h>
+#include <asm/pal.h>
+#include <asm/system.h>
+#include <asm/pgtable.h>
+#include <asm/atomic.h>
+#include <asm/tlbflush.h>
+#include <asm/uncached.h>
+#include <asm/sn/addrs.h>
+#include <asm/sn/arch.h>
+#include <asm/sn/mspec.h>
+#include <asm/sn/sn_cpuid.h>
+#include <asm/sn/io.h>
+#include <asm/sn/bte.h>
+#include <asm/sn/shubio.h>
+
+
+#define FETCHOP_ID	"Fetchop,"
+#define CACHED_ID	"Cached,"
+#define UNCACHED_ID	"Uncached"
+#define REVISION	"3.0"
+#define MSPEC_BASENAME	"mspec"
+
+/*
+ * Page types allocated by the device.
+ */
+enum {
+	MSPEC_FETCHOP = 1,
+	MSPEC_CACHED,
+	MSPEC_UNCACHED
+};
+
+/*
+ * One of these structures is allocated when an mspec region is mmaped. The
+ * structure is pointed to by the vma->vm_private_data field in the vma struct.
+ * This structure is used to record the addresses of the mspec pages.
+ */
+struct vma_data {
+	atomic_t refcnt;	/* Number of vmas sharing the data. */
+	spinlock_t lock;	/* Serialize access to the vma. */
+	int count;		/* Number of pages allocated. */
+	int type;		/* Type of pages allocated. */
+	unsigned long maddr[0];	/* Array of MSPEC addresses. */
+};
+
+/*
+ * Memory Special statistics.
+ */
+struct mspec_stats {
+	atomic_t map_count;	/* Number of active mmap's */
+	atomic_t pages_in_use;	/* Number of mspec pages in use */
+	unsigned long pages_total;	/* Total number of mspec pages */
+};
+
+static struct mspec_stats mspec_stats;
+
+static inline int
+mspec_zero_block(unsigned long addr, int len)
+{
+	int status;
+
+	if (ia64_platform_is("sn2"))
+		status = bte_copy(0, addr & ~__IA64_UNCACHED_OFFSET, len,
+				  BTE_WACQUIRE | BTE_ZERO_FILL, NULL);
+	else {
+		memset((char *) addr, 0, len);
+		status = 0;
+	}
+	return status;
+}
+
+/*
+ * mspec_open
+ *
+ * Called when a device mapping is created by a means other than mmap
+ * (via fork, etc.).  Increments the reference count on the underlying
+ * mspec data so it is not freed prematurely.
+ */
+static void
+mspec_open(struct vm_area_struct *vma)
+{
+	struct vma_data *vdata;
+
+	vdata = vma->vm_private_data;
+	atomic_inc(&vdata->refcnt);
+}
+
+/*
+ * mspec_close
+ *
+ * Called when unmapping a device mapping. Frees all mspec pages
+ * belonging to the vma.
+ */
+static void
+mspec_close(struct vm_area_struct *vma)
+{
+	struct vma_data *vdata;
+	int i, pages, result;
+
+	vdata = vma->vm_private_data;
+	if (atomic_dec_and_test(&vdata->refcnt)) {
+		pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+		for (i = 0; i < pages; i++) {
+			if (vdata->maddr[i] != 0) {
+				/*
+				 * Clear the page before sticking it back
+				 * into the pool.
+				 */
+				result =
+				    mspec_zero_block(vdata->maddr[i],
+						     PAGE_SIZE);
+				if (!result) {
+					uncached_free_page(vdata->
+							   maddr[i]);
+					atomic_dec(&mspec_stats.
+						   pages_in_use);
+				} else
+					printk(KERN_WARNING
+					       "mspec_close(): "
+					       "failed to zero page %i\n",
+					       result);
+			}
+		}
+
+		if (vdata->count)
+			atomic_dec(&mspec_stats.map_count);
+		vfree(vdata);
+	}
+}
+
+/*
+ * mspec_get_one_pte
+ *
+ * Return the pte for a given mm and address.
+ */
+static __inline__ int
+mspec_get_one_pte(struct mm_struct *mm, u64 address, pte_t ** page_table)
+{
+	pgd_t *pgd;
+	pmd_t *pmd;
+	pud_t *pud;
+
+	pgd = pgd_offset(mm, address);
+	if (pgd_present(*pgd)) {
+		pud = pud_offset(pgd, address);
+		if (pud_present(*pud)) {
+			pmd = pmd_offset(pud, address);
+			if (pmd_present(*pmd)) {
+				*page_table = pte_offset_map(pmd, address);
+				if (pte_present(**page_table)) {
+					return 0;
+				}
+			}
+		}
+	}
+
+	return -1;
+}
+
+/*
+ * mspec_nopage
+ *
+ * Creates a mspec page and maps it to user space.
+ */
+static struct page *
+mspec_nopage(struct vm_area_struct *vma,
+	     unsigned long address, int *unused)
+{
+	unsigned long paddr, maddr = 0;
+	unsigned long pfn;
+	int index;
+	pte_t *page_table, pte;
+	struct vma_data *vdata = vma->vm_private_data;
+
+	index = (address - vma->vm_start) >> PAGE_SHIFT;
+	if ((volatile unsigned long) vdata->maddr[index] == 0) {
+		maddr = uncached_alloc_page(numa_node_id());
+		if (maddr == 0)
+			return NOPAGE_SIGBUS;	/* NOPAGE_OOM ??? */
+
+		spin_lock(&vdata->lock);
+		if (vdata->maddr[index] == 0) {
+			atomic_inc(&mspec_stats.pages_in_use);
+			vdata->count++;
+
+			vdata->maddr[index] = maddr;
+			maddr = 0;
+		}
+		spin_unlock(&vdata->lock);
+
+		/* Release any unneeded page */
+		if (maddr)
+			uncached_free_page(maddr);
+	}
+
+	spin_lock(&vma->vm_mm->page_table_lock);
+	if (mspec_get_one_pte(vma->vm_mm, address, &page_table) != 0) {
+		if (vdata->type == MSPEC_FETCHOP)
+			paddr = TO_AMO(vdata->maddr[index]);
+		else
+			paddr = __pa(TO_CAC(vdata->maddr[index]));
+
+		pfn = paddr >> PAGE_SHIFT;
+		pte = pfn_pte(pfn, vma->vm_page_prot);
+		pte = pte_mkwrite(pte_mkdirty(pte));
+		set_pte(page_table, pte);
+	}
+	spin_unlock(&vma->vm_mm->page_table_lock);
+
+	return NOPAGE_FAULTED;
+}
+
+static struct vm_operations_struct mspec_vm_ops = {
+	.open mspec_open,
+	.close mspec_close,
+	.nopage mspec_nopage
+};
+
+/*
+ * mspec_mmap
+ *
+ * Called when mmaping the device.  Initializes the vma with a fault handler
+ * and private data structure necessary to allocate, track, and free the
+ * underlying pages.
+ */
+static int
+mspec_mmap(struct file *file, struct vm_area_struct *vma, int type)
+{
+	struct vma_data *vdata;
+	int pages;
+
+	if (vma->vm_pgoff != 0)
+		return -EINVAL;
+
+	if ((vma->vm_flags & VM_WRITE) == 0)
+		return -EPERM;
+
+	pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+	if (!
+	    (vdata =
+	     vmalloc(sizeof(struct vma_data) + pages * sizeof(long))))
+		return -ENOMEM;
+	memset(vdata, 0, sizeof(struct vma_data) + pages * sizeof(long));
+
+	vdata->type = type;
+	spin_lock_init(&vdata->lock);
+	vdata->refcnt = ATOMIC_INIT(1);
+	vma->vm_private_data = vdata;
+
+	vma->vm_flags |= (VM_IO | VM_SHM | VM_LOCKED | VM_RESERVED);
+	if (vdata->type == MSPEC_FETCHOP || vdata->type == MSPEC_UNCACHED)
+		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vma->vm_ops = &mspec_vm_ops;
+
+	atomic_inc(&mspec_stats.map_count);
+	return 0;
+}
+
+static int
+fetchop_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	return mspec_mmap(file, vma, MSPEC_FETCHOP);
+}
+
+static int
+cached_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	return mspec_mmap(file, vma, MSPEC_CACHED);
+}
+
+static int
+uncached_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	return mspec_mmap(file, vma, MSPEC_UNCACHED);
+}
+
+#ifdef CONFIG_PROC_FS
+static void *
+mspec_seq_start(struct seq_file *file, loff_t * offset)
+{
+	if (*offset < MAX_NUMNODES)
+		return offset;
+	return NULL;
+}
+
+static void *
+mspec_seq_next(struct seq_file *file, void *data, loff_t * offset)
+{
+	(*offset)++;
+	if (*offset < MAX_NUMNODES)
+		return offset;
+	return NULL;
+}
+
+static void
+mspec_seq_stop(struct seq_file *file, void *data)
+{
+}
+
+static int
+mspec_seq_show(struct seq_file *file, void *data)
+{
+	int i;
+
+	i = *(loff_t *) data;
+
+	if (!i) {
+		seq_printf(file, "mappings               : %i\n",
+			   atomic_read(&mspec_stats.map_count));
+		seq_printf(file, "current mspec pages    : %i\n",
+			   atomic_read(&mspec_stats.pages_in_use));
+		seq_printf(file, "%4s %7s %7s\n", "node", "total", "free");
+	}
+	return 0;
+}
+
+static struct seq_operations mspec_seq_ops = {
+	.start = mspec_seq_start,
+	.next = mspec_seq_next,
+	.stop = mspec_seq_stop,
+	.show = mspec_seq_show
+};
+
+int
+mspec_proc_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &mspec_seq_ops);
+}
+
+static struct file_operations proc_mspec_operations = {
+	.open = mspec_proc_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release,
+};
+
+static struct proc_dir_entry *proc_mspec;
+
+#endif	/* CONFIG_PROC_FS */
+
+static struct file_operations fetchop_fops = {
+	.owner THIS_MODULE,
+	.mmap fetchop_mmap
+};
+
+static struct miscdevice fetchop_miscdev = {
+	.minor MISC_DYNAMIC_MINOR,
+	.name "sgi_fetchop",
+	.fops & fetchop_fops
+};
+
+static struct file_operations cached_fops = {
+	.owner THIS_MODULE,
+	.mmap cached_mmap
+};
+
+static struct miscdevice cached_miscdev = {
+	.minor MISC_DYNAMIC_MINOR,
+	.name "sgi_cached",
+	.fops & cached_fops
+};
+
+static struct file_operations uncached_fops = {
+	.owner THIS_MODULE,
+	.mmap uncached_mmap
+};
+
+static struct miscdevice uncached_miscdev = {
+	.minor MISC_DYNAMIC_MINOR,
+	.name "sgi_uncached",
+	.fops & uncached_fops
+};
+
+/*
+ * mspec_init
+ *
+ * Called at boot time to initialize the mspec facility.
+ */
+static int __init
+mspec_init(void)
+{
+	int ret;
+
+	/*
+	 * The fetchop device only works on SN2 hardware, uncached and cached
+	 * memory drivers should both be valid on all ia64 hardware
+	 */
+	if (ia64_platform_is("sn2")) {
+		if ((ret = misc_register(&fetchop_miscdev))) {
+			printk(KERN_ERR
+			       "%s: failed to register device %i\n",
+			       FETCHOP_ID, ret);
+			return ret;
+		}
+	}
+	if ((ret = misc_register(&cached_miscdev))) {
+		printk(KERN_ERR "%s: failed to register device %i\n",
+		       CACHED_ID, ret);
+		misc_deregister(&fetchop_miscdev);
+		return ret;
+	}
+	if ((ret = misc_register(&uncached_miscdev))) {
+		printk(KERN_ERR "%s: failed to register device %i\n",
+		       UNCACHED_ID, ret);
+		misc_deregister(&cached_miscdev);
+		misc_deregister(&fetchop_miscdev);
+		return ret;
+	}
+
+	/*
+	 * /proc code needs to be updated to work with the new
+	 * allocation scheme
+	 */
+#ifdef CONFIG_PROC_FS
+	if (!(proc_mspec = create_proc_entry(MSPEC_BASENAME, 0444, NULL))) {
+		printk(KERN_ERR "%s: unable to create proc entry",
+		       MSPEC_BASENAME);
+		misc_deregister(&uncached_miscdev);
+		misc_deregister(&cached_miscdev);
+		misc_deregister(&fetchop_miscdev);
+		return -EINVAL;
+	}
+	proc_mspec->proc_fops = &proc_mspec_operations;
+#endif
+
+	printk(KERN_INFO "%s %s initialized devices: %s %s %s\n",
+	       MSPEC_BASENAME, REVISION,
+	       ia64_platform_is("sn2") ? FETCHOP_ID : "",
+	       CACHED_ID, UNCACHED_ID);
+
+	return 0;
+}
+
+static void __exit
+mspec_exit(void)
+{
+	WARN_ON(atomic_read(&mspec_stats.pages_in_use) > 0);
+
+#ifdef CONFIG_PROC_FS
+	remove_proc_entry(MSPEC_BASENAME, NULL);
+#endif
+	misc_deregister(&uncached_miscdev);
+	misc_deregister(&cached_miscdev);
+	misc_deregister(&fetchop_miscdev);
+}
+
+module_init(mspec_init);
+module_exit(mspec_exit);
+
+MODULE_AUTHOR("Silicon Graphics, Inc.");
+MODULE_DESCRIPTION("Driver for SGI SN special memory operations");
+MODULE_LICENSE("GPL");
-
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