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/machdep.h>
  13 #include <asm/hvcall.h>
  14
  15 bool dawr_force_enable;
  16 EXPORT_SYMBOL_GPL(dawr_force_enable);
  17
  18 int set_dawr(int nr, struct arch_hw_breakpoint *brk)
  19 {
  20         unsigned long dawr, dawrx, mrd;
  21
  22         dawr = brk->address;
  23
  24         dawrx  = (brk->type & (HW_BRK_TYPE_READ | HW_BRK_TYPE_WRITE))
  25                 << (63 - 58);
  26         dawrx |= ((brk->type & (HW_BRK_TYPE_TRANSLATE)) >> 2) << (63 - 59);
  27         dawrx |= (brk->type & (HW_BRK_TYPE_PRIV_ALL)) >> 3;
  28         /*
  29          * DAWR length is stored in field MDR bits 48:53.  Matches range in
  30          * doublewords (64 bits) baised by -1 eg. 0b000000=1DW and
  31          * 0b111111=64DW.
  32          * brk->hw_len is in bytes.
  33          * This aligns up to double word size, shifts and does the bias.
  34          */
  35         mrd = ((brk->hw_len + 7) >> 3) - 1;
  36         dawrx |= (mrd & 0x3f) << (63 - 53);
  37
  38         if (ppc_md.set_dawr)
  39                 return ppc_md.set_dawr(nr, dawr, dawrx);
  40
  41         if (nr == 0) {
  42                 mtspr(SPRN_DAWR0, dawr);
  43                 mtspr(SPRN_DAWRX0, dawrx);
  44         } else {
  45                 mtspr(SPRN_DAWR1, dawr);
  46                 mtspr(SPRN_DAWRX1, dawrx);
  47         }
  48
  49         return 0;
  50 }
  51
  52 static void disable_dawrs_cb(void *info)
  53 {
  54         struct arch_hw_breakpoint null_brk = {0};
  55         int i;
  56
  57         for (i = 0; i < nr_wp_slots(); i++)
  58                 set_dawr(i, &null_brk);
  59 }
  60
  61 static ssize_t dawr_write_file_bool(struct file *file,
  62                                     const char __user *user_buf,
  63                                     size_t count, loff_t *ppos)
  64 {
  65         struct arch_hw_breakpoint null_brk = {0};
  66         size_t rc;
  67
  68         /* Send error to user if they hypervisor won't allow us to write DAWR */
  69         if (!dawr_force_enable &&
  70             firmware_has_feature(FW_FEATURE_LPAR) &&
  71             set_dawr(0, &null_brk) != H_SUCCESS)
  72                 return -ENODEV;
  73
  74         rc = debugfs_write_file_bool(file, user_buf, count, ppos);
  75         if (rc)
  76                 return rc;
  77
  78         /* If we are clearing, make sure all CPUs have the DAWR cleared */
  79         if (!dawr_force_enable)
  80                 smp_call_function(disable_dawrs_cb, NULL, 0);
  81
  82         return rc;
  83 }
  84
  85 static const struct file_operations dawr_enable_fops = {
  86         .read =         debugfs_read_file_bool,
  87         .write =        dawr_write_file_bool,
  88         .open =         simple_open,
  89         .llseek =       default_llseek,
  90 };
  91
  92 static int __init dawr_force_setup(void)
  93 {
  94         if (cpu_has_feature(CPU_FTR_DAWR)) {
  95                 /* Don't setup sysfs file for user control on P8 */
  96                 dawr_force_enable = true;
  97                 return 0;
  98         }
  99
 100         if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
 101                 /* Turn DAWR off by default, but allow admin to turn it on */
 102                 debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
 103                                            arch_debugfs_dir,
 104                                            &dawr_force_enable,
 105                                            &dawr_enable_fops);
 106         }
 107         return 0;
 108 }
 109 arch_initcall(dawr_force_setup);