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(int nr, 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(nr, dawr, dawrx);
  41
  42         if (nr == 0) {
  43                 mtspr(SPRN_DAWR0, dawr);
  44                 mtspr(SPRN_DAWRX0, dawrx);
  45         } else {
  46                 mtspr(SPRN_DAWR1, dawr);
  47                 mtspr(SPRN_DAWRX1, dawrx);
  48         }
  49
  50         return 0;
  51 }
  52
  53 static void disable_dawrs_cb(void *info)
  54 {
  55         struct arch_hw_breakpoint null_brk = {0};
  56         int i;
  57
  58         for (i = 0; i < nr_wp_slots(); i++)
  59                 set_dawr(i, &null_brk);
  60 }
  61
  62 static ssize_t dawr_write_file_bool(struct file *file,
  63                                     const char __user *user_buf,
  64                                     size_t count, loff_t *ppos)
  65 {
  66         struct arch_hw_breakpoint null_brk = {0};
  67         size_t rc;
  68
  69         /* Send error to user if they hypervisor won't allow us to write DAWR */
  70         if (!dawr_force_enable &&
  71             firmware_has_feature(FW_FEATURE_LPAR) &&
  72             set_dawr(0, &null_brk) != H_SUCCESS)
  73                 return -ENODEV;
  74
  75         rc = debugfs_write_file_bool(file, user_buf, count, ppos);
  76         if (rc)
  77                 return rc;
  78
  79         /* If we are clearing, make sure all CPUs have the DAWR cleared */
  80         if (!dawr_force_enable)
  81                 smp_call_function(disable_dawrs_cb, NULL, 0);
  82
  83         return rc;
  84 }
  85
  86 static const struct file_operations dawr_enable_fops = {
  87         .read =         debugfs_read_file_bool,
  88         .write =        dawr_write_file_bool,
  89         .open =         simple_open,
  90         .llseek =       default_llseek,
  91 };
  92
  93 static int __init dawr_force_setup(void)
  94 {
  95         if (cpu_has_feature(CPU_FTR_DAWR)) {
  96                 /* Don't setup sysfs file for user control on P8 */
  97                 dawr_force_enable = true;
  98                 return 0;
  99         }
 100
 101         if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
 102                 /* Turn DAWR off by default, but allow admin to turn it on */
 103                 debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
 104                                            powerpc_debugfs_root,
 105                                            &dawr_force_enable,
 106                                            &dawr_enable_fops);
 107         }
 108         return 0;
 109 }
 110 arch_initcall(dawr_force_setup);