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