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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 
xor_block(u8 * p1,u8 * p2)12 static 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. */
raid6_2data_recov_s390xc(int disks,size_t bytes,int faila,int failb,void ** ptrs)23 static 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 */
raid6_datap_recov_s390xc(int disks,size_t bytes,int faila,void ** ptrs)72 static 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 
111 const 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