From f5b55fa1f81d518925d68b50d2316850c525d1ad Mon Sep 17 00:00:00 2001
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Wed, 31 Aug 2016 09:27:35 +0200
Subject: RAID/s390: provide raid6 recovery optimization

The XC instruction can be used to improve the speed of the raid6
recovery. The loops now operate on blocks of 256 bytes.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 lib/raid6/recov_s390xc.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)
 create mode 100644 lib/raid6/recov_s390xc.c

(limited to 'lib/raid6/recov_s390xc.c')

diff --git a/lib/raid6/recov_s390xc.c b/lib/raid6/recov_s390xc.c
new file mode 100644
index 000000000000..b042dac826cc
--- /dev/null
+++ b/lib/raid6/recov_s390xc.c
@@ -0,0 +1,116 @@
+/*
+ * 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/export.h>
+#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] = (void *)raid6_empty_zero_page;
+	ptrs[disks-2] = dp;
+	dq = (u8 *)ptrs[failb];
+	ptrs[failb] = (void *)raid6_empty_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] = (void *)raid6_empty_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,
+};
-- 
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