// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Virtual Processor Dispatch Trace Log
 *
 * (C) Copyright IBM Corporation 2009
 *
 * Author: Jeremy Kerr <jk@ozlabs.org>
 */

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <asm/smp.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <asm/firmware.h>
#include <asm/dtl.h>
#include <asm/lppaca.h>
#include <asm/plpar_wrappers.h>
#include <asm/machdep.h>

struct dtl {
        struct dtl_entry        *buf;
        int                     cpu;
        int                     buf_entries;
        u64                     last_idx;
        spinlock_t              lock;
};
static DEFINE_PER_CPU(struct dtl, cpu_dtl);

static u8 dtl_event_mask = DTL_LOG_ALL;


/*
 * Size of per-cpu log buffers. Firmware requires that the buffer does
 * not cross a 4k boundary.
 */
static int dtl_buf_entries = N_DISPATCH_LOG;

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
struct dtl_ring {
        u64     write_index;
        struct dtl_entry *write_ptr;
        struct dtl_entry *buf;
        struct dtl_entry *buf_end;
};

static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);

static atomic_t dtl_count;

/*
 * The cpu accounting code controls the DTL ring buffer, and we get
 * given entries as they are processed.
 */
static void consume_dtle(struct dtl_entry *dtle, u64 index)
{
        struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
        struct dtl_entry *wp = dtlr->write_ptr;
        struct lppaca *vpa = local_paca->lppaca_ptr;

        if (!wp)
                return;

        *wp = *dtle;
        barrier();

        /* check for hypervisor ring buffer overflow, ignore this entry if so */
        if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
                return;

        ++wp;
        if (wp == dtlr->buf_end)
                wp = dtlr->buf;
        dtlr->write_ptr = wp;

        /* incrementing write_index makes the new entry visible */
        smp_wmb();
        ++dtlr->write_index;
}

static int dtl_start(struct dtl *dtl)
{
        struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);

        dtlr->buf = dtl->buf;
        dtlr->buf_end = dtl->buf + dtl->buf_entries;
        dtlr->write_index = 0;

        /* setting write_ptr enables logging into our buffer */
        smp_wmb();
        dtlr->write_ptr = dtl->buf;

        /* enable event logging */
        lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;

        dtl_consumer = consume_dtle;
        atomic_inc(&dtl_count);
        return 0;
}

static void dtl_stop(struct dtl *dtl)
{
        struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);

        dtlr->write_ptr = NULL;
        smp_wmb();

        dtlr->buf = NULL;

        /* restore dtl_enable_mask */
        lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;

        if (atomic_dec_and_test(&dtl_count))
                dtl_consumer = NULL;
}

static u64 dtl_current_index(struct dtl *dtl)
{
        return per_cpu(dtl_rings, dtl->cpu).write_index;
}

#else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

static int dtl_start(struct dtl *dtl)
{
        unsigned long addr;
        int ret, hwcpu;

        /* Register our dtl buffer with the hypervisor. The HV expects the
         * buffer size to be passed in the second word of the buffer */
        ((u32 *)dtl->buf)[1] = cpu_to_be32(DISPATCH_LOG_BYTES);

        hwcpu = get_hard_smp_processor_id(dtl->cpu);
        addr = __pa(dtl->buf);
        ret = register_dtl(hwcpu, addr);
        if (ret) {
                printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
                       "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
                return -EIO;
        }

        /* set our initial buffer indices */
        lppaca_of(dtl->cpu).dtl_idx = 0;

        /* ensure that our updates to the lppaca fields have occurred before
         * we actually enable the logging */
        smp_wmb();

        /* enable event logging */
        lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;

        return 0;
}

static void dtl_stop(struct dtl *dtl)
{
        int hwcpu = get_hard_smp_processor_id(dtl->cpu);

        lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;

        unregister_dtl(hwcpu);
}

static u64 dtl_current_index(struct dtl *dtl)
{
        return be64_to_cpu(lppaca_of(dtl->cpu).dtl_idx);
}
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

static int dtl_enable(struct dtl *dtl)
{
        long int n_entries;
        long int rc;
        struct dtl_entry *buf = NULL;

        if (!dtl_cache)
                return -ENOMEM;

        /* only allow one reader */
        if (dtl->buf)
                return -EBUSY;

        /* ensure there are no other conflicting dtl users */
        if (!read_trylock(&dtl_access_lock))
                return -EBUSY;

        n_entries = dtl_buf_entries;
        buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
        if (!buf) {
                printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
                                __func__, dtl->cpu);
                read_unlock(&dtl_access_lock);
                return -ENOMEM;
        }

        spin_lock(&dtl->lock);
        rc = -EBUSY;
        if (!dtl->buf) {
                /* store the original allocation size for use during read */
                dtl->buf_entries = n_entries;
                dtl->buf = buf;
                dtl->last_idx = 0;
                rc = dtl_start(dtl);
                if (rc)
                        dtl->buf = NULL;
        }
        spin_unlock(&dtl->lock);

        if (rc) {
                read_unlock(&dtl_access_lock);
                kmem_cache_free(dtl_cache, buf);
        }

        return rc;
}

static void dtl_disable(struct dtl *dtl)
{
        spin_lock(&dtl->lock);
        dtl_stop(dtl);
        kmem_cache_free(dtl_cache, dtl->buf);
        dtl->buf = NULL;
        dtl->buf_entries = 0;
        spin_unlock(&dtl->lock);
        read_unlock(&dtl_access_lock);
}

/* file interface */

static int dtl_file_open(struct inode *inode, struct file *filp)
{
        struct dtl *dtl = inode->i_private;
        int rc;

        rc = dtl_enable(dtl);
        if (rc)
                return rc;

        filp->private_data = dtl;
        return 0;
}

static int dtl_file_release(struct inode *inode, struct file *filp)
{
        struct dtl *dtl = inode->i_private;
        dtl_disable(dtl);
        return 0;
}

static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
                loff_t *pos)
{
        long int rc, n_read, n_req, read_size;
        struct dtl *dtl;
        u64 cur_idx, last_idx, i;

        if ((len % sizeof(struct dtl_entry)) != 0)
                return -EINVAL;

        dtl = filp->private_data;

        /* requested number of entries to read */
        n_req = len / sizeof(struct dtl_entry);

        /* actual number of entries read */
        n_read = 0;

        spin_lock(&dtl->lock);

        cur_idx = dtl_current_index(dtl);
        last_idx = dtl->last_idx;

        if (last_idx + dtl->buf_entries <= cur_idx)
                last_idx = cur_idx - dtl->buf_entries + 1;

        if (last_idx + n_req > cur_idx)
                n_req = cur_idx - last_idx;

        if (n_req > 0)
                dtl->last_idx = last_idx + n_req;

        spin_unlock(&dtl->lock);

        if (n_req <= 0)
                return 0;

        i = last_idx % dtl->buf_entries;

        /* read the tail of the buffer if we've wrapped */
        if (i + n_req > dtl->buf_entries) {
                read_size = dtl->buf_entries - i;

                rc = copy_to_user(buf, &dtl->buf[i],
                                read_size * sizeof(struct dtl_entry));
                if (rc)
                        return -EFAULT;

                i = 0;
                n_req -= read_size;
                n_read += read_size;
                buf += read_size * sizeof(struct dtl_entry);
        }

        /* .. and now the head */
        rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
        if (rc)
                return -EFAULT;

        n_read += n_req;

        return n_read * sizeof(struct dtl_entry);
}

static const struct file_operations dtl_fops = {
        .open           = dtl_file_open,
        .release        = dtl_file_release,
        .read           = dtl_file_read,
        .llseek         = no_llseek,
};

static struct dentry *dtl_dir;

static void dtl_setup_file(struct dtl *dtl)
{
        char name[10];

        sprintf(name, "cpu-%d", dtl->cpu);

        debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
}

static int dtl_init(void)
{
        int i;

        if (!firmware_has_feature(FW_FEATURE_SPLPAR))
                return -ENODEV;

        /* set up common debugfs structure */

        dtl_dir = debugfs_create_dir("dtl", arch_debugfs_dir);

        debugfs_create_x8("dtl_event_mask", 0600, dtl_dir, &dtl_event_mask);
        debugfs_create_u32("dtl_buf_entries", 0400, dtl_dir, &dtl_buf_entries);

        /* set up the per-cpu log structures */
        for_each_possible_cpu(i) {
                struct dtl *dtl = &per_cpu(cpu_dtl, i);
                spin_lock_init(&dtl->lock);
                dtl->cpu = i;

                dtl_setup_file(dtl);
        }

        return 0;
}
machine_arch_initcall(pseries, dtl_init);