1// SPDX-License-Identifier: GPL-2.0
2/*
3 * RAID-6 data recovery in dual failure mode based on the XC instruction.
4 *
5 * Copyright IBM Corp. 2016
6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
7 */
8
9#include <linux/export.h>
10#include <linux/raid/pq.h>
11
12static inline void xor_block(u8 *p1, u8 *p2)
13{
14	typedef struct { u8 _[256]; } addrtype;
15
16	asm volatile(
17		"	xc	0(256,%[p1]),0(%[p2])\n"
18		: "+m" (*(addrtype *) p1) : "m" (*(addrtype *) p2),
19		  [p1] "a" (p1), [p2] "a" (p2) : "cc");
20}
21
22/* Recover two failed data blocks. */
23static void raid6_2data_recov_s390xc(int disks, size_t bytes, int faila,
24		int failb, void **ptrs)
25{
26	u8 *p, *q, *dp, *dq;
27	const u8 *pbmul;	/* P multiplier table for B data */
28	const u8 *qmul;		/* Q multiplier table (for both) */
29	int i;
30
31	p = (u8 *)ptrs[disks-2];
32	q = (u8 *)ptrs[disks-1];
33
34	/* Compute syndrome with zero for the missing data pages
35	   Use the dead data pages as temporary storage for
36	   delta p and delta q */
37	dp = (u8 *)ptrs[faila];
38	ptrs[faila] = (void *)raid6_empty_zero_page;
39	ptrs[disks-2] = dp;
40	dq = (u8 *)ptrs[failb];
41	ptrs[failb] = (void *)raid6_empty_zero_page;
42	ptrs[disks-1] = dq;
43
44	raid6_call.gen_syndrome(disks, bytes, ptrs);
45
46	/* Restore pointer table */
47	ptrs[faila]   = dp;
48	ptrs[failb]   = dq;
49	ptrs[disks-2] = p;
50	ptrs[disks-1] = q;
51
52	/* Now, pick the proper data tables */
53	pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
54	qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];
55
56	/* Now do it... */
57	while (bytes) {
58		xor_block(dp, p);
59		xor_block(dq, q);
60		for (i = 0; i < 256; i++)
61			dq[i] = pbmul[dp[i]] ^ qmul[dq[i]];
62		xor_block(dp, dq);
63		p += 256;
64		q += 256;
65		dp += 256;
66		dq += 256;
67		bytes -= 256;
68	}
69}
70
71/* Recover failure of one data block plus the P block */
72static void raid6_datap_recov_s390xc(int disks, size_t bytes, int faila,
73		void **ptrs)
74{
75	u8 *p, *q, *dq;
76	const u8 *qmul;		/* Q multiplier table */
77	int i;
78
79	p = (u8 *)ptrs[disks-2];
80	q = (u8 *)ptrs[disks-1];
81
82	/* Compute syndrome with zero for the missing data page
83	   Use the dead data page as temporary storage for delta q */
84	dq = (u8 *)ptrs[faila];
85	ptrs[faila] = (void *)raid6_empty_zero_page;
86	ptrs[disks-1] = dq;
87
88	raid6_call.gen_syndrome(disks, bytes, ptrs);
89
90	/* Restore pointer table */
91	ptrs[faila]   = dq;
92	ptrs[disks-1] = q;
93
94	/* Now, pick the proper data tables */
95	qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];
96
97	/* Now do it... */
98	while (bytes) {
99		xor_block(dq, q);
100		for (i = 0; i < 256; i++)
101			dq[i] = qmul[dq[i]];
102		xor_block(p, dq);
103		p += 256;
104		q += 256;
105		dq += 256;
106		bytes -= 256;
107	}
108}
109
110
111const struct raid6_recov_calls raid6_recov_s390xc = {
112	.data2 = raid6_2data_recov_s390xc,
113	.datap = raid6_datap_recov_s390xc,
114	.valid = NULL,
115	.name = "s390xc",
116	.priority = 1,
117};
118