// SPDX-License-Identifier: GPL-2.0
/*
 * RAID-6 data recovery in dual failure mode based on the XC instruction.
 *
 * Copyright IBM Corp. 2016
 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/raid/pq.h>

static inline void xor_block(u8 *p1, u8 *p2)
{
        typedef struct { u8 _[256]; } addrtype;

        asm volatile(
                "       xc      0(256,%[p1]),0(%[p2])\n"
                : "+m" (*(addrtype *) p1) : "m" (*(addrtype *) p2),
                  [p1] "a" (p1), [p2] "a" (p2) : "cc");
}

/* Recover two failed data blocks. */
static void raid6_2data_recov_s390xc(int disks, size_t bytes, int faila,
                int failb, void **ptrs)
{
        u8 *p, *q, *dp, *dq;
        const u8 *pbmul;        /* P multiplier table for B data */
        const u8 *qmul;         /* Q multiplier table (for both) */
        int i;

        p = (u8 *)ptrs[disks-2];
        q = (u8 *)ptrs[disks-1];

        /* Compute syndrome with zero for the missing data pages
           Use the dead data pages as temporary storage for
           delta p and delta q */
        dp = (u8 *)ptrs[faila];
        ptrs[faila] = raid6_get_zero_page();
        ptrs[disks-2] = dp;
        dq = (u8 *)ptrs[failb];
        ptrs[failb] = raid6_get_zero_page();
        ptrs[disks-1] = dq;

        raid6_call.gen_syndrome(disks, bytes, ptrs);

        /* Restore pointer table */
        ptrs[faila]   = dp;
        ptrs[failb]   = dq;
        ptrs[disks-2] = p;
        ptrs[disks-1] = q;

        /* Now, pick the proper data tables */
        pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
        qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];

        /* Now do it... */
        while (bytes) {
                xor_block(dp, p);
                xor_block(dq, q);
                for (i = 0; i < 256; i++)
                        dq[i] = pbmul[dp[i]] ^ qmul[dq[i]];
                xor_block(dp, dq);
                p += 256;
                q += 256;
                dp += 256;
                dq += 256;
                bytes -= 256;
        }
}

/* Recover failure of one data block plus the P block */
static void raid6_datap_recov_s390xc(int disks, size_t bytes, int faila,
                void **ptrs)
{
        u8 *p, *q, *dq;
        const u8 *qmul;         /* Q multiplier table */
        int i;

        p = (u8 *)ptrs[disks-2];
        q = (u8 *)ptrs[disks-1];

        /* Compute syndrome with zero for the missing data page
           Use the dead data page as temporary storage for delta q */
        dq = (u8 *)ptrs[faila];
        ptrs[faila] = raid6_get_zero_page();
        ptrs[disks-1] = dq;

        raid6_call.gen_syndrome(disks, bytes, ptrs);

        /* Restore pointer table */
        ptrs[faila]   = dq;
        ptrs[disks-1] = q;

        /* Now, pick the proper data tables */
        qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];

        /* Now do it... */
        while (bytes) {
                xor_block(dq, q);
                for (i = 0; i < 256; i++)
                        dq[i] = qmul[dq[i]];
                xor_block(p, dq);
                p += 256;
                q += 256;
                dq += 256;
                bytes -= 256;
        }
}


const struct raid6_recov_calls raid6_recov_s390xc = {
        .data2 = raid6_2data_recov_s390xc,
        .datap = raid6_datap_recov_s390xc,
        .valid = NULL,
        .name = "s390xc",
        .priority = 1,
};