powerpc: Add virtual processor dispatch trace log
pseries SPLPAR machines are able to retrieve a log of dispatch and preempt events from the hypervisor. With this information, we can see when and why each dispatch & preempt is occuring. This change adds a set of debugfs files allowing userspace to read this dispatch log. Based on initial patches from Nishanth Aravamudan <nacc@us.ibm.com>. Signed-off-by: Jeremy Kerr <jk@ozlabs.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Jeremy Kerr
Benjamin Herrenschmidt
parent
098e8957af
commit
fc59a3fc8e
4 changed files with 295 additions and 0 deletions
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@ -68,3 +68,13 @@ config CMM
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makes sense for a system running in an LPAR where the unused pages
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will be reused for other LPARs. The interface allows firmware to
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balance memory across many LPARs.
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config DTL
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bool "Dispatch Trace Log"
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depends on PPC_SPLPAR && DEBUG_FS
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help
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SPLPAR machines can log hypervisor preempt & dispatch events to a
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kernel buffer. Saying Y here will enable logging these events,
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which are accessible through a debugfs file.
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Say N if you are unsure.
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@ -25,3 +25,4 @@ obj-$(CONFIG_HVCS) += hvcserver.o
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obj-$(CONFIG_HCALL_STATS) += hvCall_inst.o
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obj-$(CONFIG_PHYP_DUMP) += phyp_dump.o
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obj-$(CONFIG_CMM) += cmm.o
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obj-$(CONFIG_DTL) += dtl.o
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274
arch/powerpc/platforms/pseries/dtl.c
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274
arch/powerpc/platforms/pseries/dtl.c
Normal file
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@ -0,0 +1,274 @@
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/*
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* Virtual Processor Dispatch Trace Log
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*
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* (C) Copyright IBM Corporation 2009
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*
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* Author: Jeremy Kerr <jk@ozlabs.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/init.h>
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#include <linux/debugfs.h>
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#include <asm/smp.h>
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#include <asm/system.h>
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#include <asm/uaccess.h>
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#include "plpar_wrappers.h"
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/*
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* Layout of entries in the hypervisor's DTL buffer. Although we don't
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* actually access the internals of an entry (we only need to know the size),
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* we might as well define it here for reference.
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*/
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struct dtl_entry {
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u8 dispatch_reason;
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u8 preempt_reason;
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u16 processor_id;
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u32 enqueue_to_dispatch_time;
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u32 ready_to_enqueue_time;
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u32 waiting_to_ready_time;
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u64 timebase;
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u64 fault_addr;
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u64 srr0;
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u64 srr1;
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};
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struct dtl {
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struct dtl_entry *buf;
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struct dentry *file;
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int cpu;
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int buf_entries;
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u64 last_idx;
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};
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static DEFINE_PER_CPU(struct dtl, dtl);
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/*
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* Dispatch trace log event mask:
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* 0x7: 0x1: voluntary virtual processor waits
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* 0x2: time-slice preempts
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* 0x4: virtual partition memory page faults
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*/
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static u8 dtl_event_mask = 0x7;
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/*
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* Size of per-cpu log buffers. Default is just under 16 pages worth.
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*/
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static int dtl_buf_entries = (16 * 85);
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static int dtl_enable(struct dtl *dtl)
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{
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unsigned long addr;
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int ret, hwcpu;
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/* only allow one reader */
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if (dtl->buf)
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return -EBUSY;
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/* we need to store the original allocation size for use during read */
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dtl->buf_entries = dtl_buf_entries;
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dtl->buf = kmalloc_node(dtl->buf_entries * sizeof(struct dtl_entry),
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GFP_KERNEL, cpu_to_node(dtl->cpu));
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if (!dtl->buf) {
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printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
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__func__, dtl->cpu);
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return -ENOMEM;
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}
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/* Register our dtl buffer with the hypervisor. The HV expects the
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* buffer size to be passed in the second word of the buffer */
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((u32 *)dtl->buf)[1] = dtl->buf_entries * sizeof(struct dtl_entry);
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hwcpu = get_hard_smp_processor_id(dtl->cpu);
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addr = __pa(dtl->buf);
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ret = register_dtl(hwcpu, addr);
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if (ret) {
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printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
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"failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
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kfree(dtl->buf);
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return -EIO;
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}
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/* set our initial buffer indices */
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dtl->last_idx = lppaca[dtl->cpu].dtl_idx = 0;
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/* enable event logging */
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lppaca[dtl->cpu].dtl_enable_mask = dtl_event_mask;
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return 0;
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}
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static void dtl_disable(struct dtl *dtl)
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{
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int hwcpu = get_hard_smp_processor_id(dtl->cpu);
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lppaca[dtl->cpu].dtl_enable_mask = 0x0;
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unregister_dtl(hwcpu, __pa(dtl->buf));
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kfree(dtl->buf);
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dtl->buf = NULL;
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dtl->buf_entries = 0;
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}
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/* file interface */
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static int dtl_file_open(struct inode *inode, struct file *filp)
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{
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struct dtl *dtl = inode->i_private;
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int rc;
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rc = dtl_enable(dtl);
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if (rc)
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return rc;
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filp->private_data = dtl;
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return 0;
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}
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static int dtl_file_release(struct inode *inode, struct file *filp)
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{
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struct dtl *dtl = inode->i_private;
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dtl_disable(dtl);
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return 0;
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}
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static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
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loff_t *pos)
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{
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int rc, cur_idx, last_idx, n_read, n_req, read_size;
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struct dtl *dtl;
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if ((len % sizeof(struct dtl_entry)) != 0)
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return -EINVAL;
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dtl = filp->private_data;
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/* requested number of entries to read */
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n_req = len / sizeof(struct dtl_entry);
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/* actual number of entries read */
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n_read = 0;
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cur_idx = lppaca[dtl->cpu].dtl_idx;
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last_idx = dtl->last_idx;
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if (cur_idx - last_idx > dtl->buf_entries) {
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pr_debug("%s: hv buffer overflow for cpu %d, samples lost\n",
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__func__, dtl->cpu);
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}
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cur_idx %= dtl->buf_entries;
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last_idx %= dtl->buf_entries;
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/* read the tail of the buffer if we've wrapped */
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if (last_idx > cur_idx) {
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read_size = min(n_req, dtl->buf_entries - last_idx);
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rc = copy_to_user(buf, &dtl->buf[last_idx],
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read_size * sizeof(struct dtl_entry));
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if (rc)
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return -EFAULT;
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last_idx = 0;
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n_req -= read_size;
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n_read += read_size;
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buf += read_size * sizeof(struct dtl_entry);
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}
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/* .. and now the head */
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read_size = min(n_req, cur_idx - last_idx);
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rc = copy_to_user(buf, &dtl->buf[last_idx],
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read_size * sizeof(struct dtl_entry));
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if (rc)
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return -EFAULT;
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n_read += read_size;
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dtl->last_idx += n_read;
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return n_read * sizeof(struct dtl_entry);
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}
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static struct file_operations dtl_fops = {
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.open = dtl_file_open,
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.release = dtl_file_release,
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.read = dtl_file_read,
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.llseek = no_llseek,
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};
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static struct dentry *dtl_dir;
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static int dtl_setup_file(struct dtl *dtl)
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{
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char name[10];
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sprintf(name, "cpu-%d", dtl->cpu);
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dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
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if (!dtl->file)
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return -ENOMEM;
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return 0;
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}
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static int dtl_init(void)
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{
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struct dentry *event_mask_file, *buf_entries_file;
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int rc, i;
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if (!firmware_has_feature(FW_FEATURE_SPLPAR))
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return -ENODEV;
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/* set up common debugfs structure */
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rc = -ENOMEM;
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dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
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if (!dtl_dir) {
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printk(KERN_WARNING "%s: can't create dtl root dir\n",
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__func__);
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goto err;
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}
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event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
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dtl_dir, &dtl_event_mask);
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buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0600,
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dtl_dir, &dtl_buf_entries);
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if (!event_mask_file || !buf_entries_file) {
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printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
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goto err_remove_dir;
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}
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/* set up the per-cpu log structures */
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for_each_possible_cpu(i) {
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struct dtl *dtl = &per_cpu(dtl, i);
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dtl->cpu = i;
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rc = dtl_setup_file(dtl);
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if (rc)
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goto err_remove_dir;
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}
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return 0;
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err_remove_dir:
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debugfs_remove_recursive(dtl_dir);
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err:
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return rc;
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}
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arch_initcall(dtl_init);
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@ -43,6 +43,16 @@ static inline long register_slb_shadow(unsigned long cpu, unsigned long vpa)
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return vpa_call(0x3, cpu, vpa);
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}
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static inline long unregister_dtl(unsigned long cpu, unsigned long vpa)
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{
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return vpa_call(0x6, cpu, vpa);
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}
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static inline long register_dtl(unsigned long cpu, unsigned long vpa)
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{
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return vpa_call(0x2, cpu, vpa);
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}
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static inline long plpar_page_set_loaned(unsigned long vpa)
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{
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unsigned long cmo_page_sz = cmo_get_page_size();
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