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

[Jack Steiner <steiner@sgi.com>]

On Wed, Oct 12, 2005 at 02:42:33PM -0500, Robin Holt wrote:
> Introduce the special memory (mspec) driver.  This is used to allow
> userland to map fetchop, etc pages
> 
> Signed-off-by: holt@sgi.com

Robin - 

I think you are missing the shub2 code that is required for flushing the fetchop 
cache. The cache is new in shub2. Take a look at the old PP4 driver - clear_mspec_page();


> 
> 
> 
> 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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-- 
Thanks

Jack Steiner (steiner@sgi.com)          651-683-5302
Principal Engineer                      SGI - Silicon Graphics, Inc.