arch/powerpc/kernel/dawr.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * DAWR infrastructure
   4  *
   5  * Copyright 2019, Michael Neuling, IBM Corporation.
   6  */
   7
   8 #include <linux/types.h>
   9 #include <linux/export.h>
  10 #include <linux/fs.h>
  11 #include <linux/debugfs.h>
  12 #include <asm/debugfs.h>
  13 #include <asm/machdep.h>
  14 #include <asm/hvcall.h>
  15
  16 bool dawr_force_enable;
  17 EXPORT_SYMBOL_GPL(dawr_force_enable);
  18
  19 int set_dawr(struct arch_hw_breakpoint *brk)
  20 {
  21         unsigned long dawr, dawrx, mrd;
  22
  23         dawr = brk->address;
  24
  25         dawrx  = (brk->type & (HW_BRK_TYPE_READ | HW_BRK_TYPE_WRITE))
  26                 << (63 - 58);
  27         dawrx |= ((brk->type & (HW_BRK_TYPE_TRANSLATE)) >> 2) << (63 - 59);
  28         dawrx |= (brk->type & (HW_BRK_TYPE_PRIV_ALL)) >> 3;
  29         /*
  30          * DAWR length is stored in field MDR bits 48:53.  Matches range in
  31          * doublewords (64 bits) baised by -1 eg. 0b000000=1DW and
  32          * 0b111111=64DW.
  33          * brk->hw_len is in bytes.
  34          * This aligns up to double word size, shifts and does the bias.
  35          */
  36         mrd = ((brk->hw_len + 7) >> 3) - 1;
  37         dawrx |= (mrd & 0x3f) << (63 - 53);
  38
  39         if (ppc_md.set_dawr)
  40                 return ppc_md.set_dawr(dawr, dawrx);
  41
  42         mtspr(SPRN_DAWR, dawr);
  43         mtspr(SPRN_DAWRX, dawrx);
  44
  45         return 0;
  46 }
  47
  48 static void set_dawr_cb(void *info)
  49 {
  50         set_dawr(info);
  51 }
  52
  53 static ssize_t dawr_write_file_bool(struct file *file,
  54                                     const char __user *user_buf,
  55                                     size_t count, loff_t *ppos)
  56 {
  57         struct arch_hw_breakpoint null_brk = {0};
  58         size_t rc;
  59
  60         /* Send error to user if they hypervisor won't allow us to write DAWR */
  61         if (!dawr_force_enable &&
  62             firmware_has_feature(FW_FEATURE_LPAR) &&
  63             set_dawr(&null_brk) != H_SUCCESS)
  64                 return -ENODEV;
  65
  66         rc = debugfs_write_file_bool(file, user_buf, count, ppos);
  67         if (rc)
  68                 return rc;
  69
  70         /* If we are clearing, make sure all CPUs have the DAWR cleared */
  71         if (!dawr_force_enable)
  72                 smp_call_function(set_dawr_cb, &null_brk, 0);
  73
  74         return rc;
  75 }
  76
  77 static const struct file_operations dawr_enable_fops = {
  78         .read =         debugfs_read_file_bool,
  79         .write =        dawr_write_file_bool,
  80         .open =         simple_open,
  81         .llseek =       default_llseek,
  82 };
  83
  84 static int __init dawr_force_setup(void)
  85 {
  86         if (cpu_has_feature(CPU_FTR_DAWR)) {
  87                 /* Don't setup sysfs file for user control on P8 */
  88                 dawr_force_enable = true;
  89                 return 0;
  90         }
  91
  92         if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
  93                 /* Turn DAWR off by default, but allow admin to turn it on */
  94                 debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
  95                                            powerpc_debugfs_root,
  96                                            &dawr_force_enable,
  97                                            &dawr_enable_fops);
  98         }
  99         return 0;
 100 }
 101 arch_initcall(dawr_force_setup);