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(i, &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(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
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("dawr_enable_dangerous", 0600,
104					   arch_debugfs_dir,
105					   &dawr_force_enable,
106					   &dawr_enable_fops);
107	}
108	return 0;
109}
110arch_initcall(dawr_force_setup);
111