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#include <asm/firmware.h>
15
16bool dawr_force_enable;
17EXPORT_SYMBOL_GPL(dawr_force_enable);
18
19int 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) biased 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
53static 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(nr: i, brk: &null_brk);
60}
61
62static 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(nr: 0, brk: &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(func: disable_dawrs_cb, NULL, wait: 0);
82
83 return rc;
84}
85
86static 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
93static 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(name: "dawr_enable_dangerous", mode: 0600,
104 parent: arch_debugfs_dir,
105 data: &dawr_force_enable,
106 fops: &dawr_enable_fops);
107 }
108 return 0;
109}
110arch_initcall(dawr_force_setup);
111

source code of linux/arch/powerpc/kernel/dawr.c