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

Robin Holt
2005-10-12T19:42:33Z

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

Signed-off-by: holt@sgi.com

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");