Btrfs: Add support for HW assisted crc32c

Intel doesn't yet ship hardware to the public with this enabled, but when they
do, they will be ready.  Original code from:

Austin Zhang <austin_zhang@linux.intel.com>

It is currently disabled, but edit crc32c.h to turn it on.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 93 insertions, 2 deletions

diff --git a/fs/btrfs/crc32c.h b/fs/btrfs/crc32c.h
index a93255b4ee27..bf6c12e85730 100644
--- a/fs/btrfs/crc32c.h
+++ b/fs/btrfs/crc32c.h
@@ -1,7 +1,95 @@
+#ifndef __BTRFS_CRC32C__
+#define __BTRFS_CRC32C__
 #include <asm/byteorder.h>
 #include <linux/crc32c.h>
 #include <linux/version.h>
 
+/* #define CONFIG_BTRFS_HW_SUM 1 */
+
+#ifdef CONFIG_BTRFS_HW_SUM
+#ifdef CONFIG_X86
+/*
+ * Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
+ * CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
+ * CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
+ * http://www.intel.com/products/processor/manuals/
+ * Intel(R) 64 and IA-32 Architectures Software Developer's Manual
+ * Volume 2A: Instruction Set Reference, A-M
+ */
+
+#include <asm/cpufeature.h>
+#include <asm/processor.h>
+
+#define X86_FEATURE_XMM4_2     (4*32+20) /* Streaming SIMD Extensions-4.2 */
+#define cpu_has_xmm4_2         boot_cpu_has(X86_FEATURE_XMM4_2)
+
+#ifdef CONFIG_X86_64
+#define REX_PRE "0x48, "
+#define SCALE_F 8
+#else
+#define REX_PRE
+#define SCALE_F 4
+#endif
+
+static inline u32 btrfs_crc32c_le_hw_byte(u32 crc, unsigned char const *data,
+                                   size_t length)
+{
+        while (length--) {
+                __asm__ __volatile__(
+                        ".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
+                        :"=S"(crc)
+                        :"0"(crc), "c"(*data)
+                );
+                data++;
+        }
+
+        return crc;
+}
+
+static inline u32 __pure btrfs_crc32c_le_hw(u32 crc, unsigned char const *p,
+                                     size_t len)
+{
+        unsigned int iquotient = len / SCALE_F;
+        unsigned int iremainder = len % SCALE_F;
+#ifdef CONFIG_X86_64
+        u64 *ptmp = (u64 *)p;
+#else
+        u32 *ptmp = (u32 *)p;
+#endif
+
+        while (iquotient--) {
+                __asm__ __volatile__(
+                        ".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
+                        :"=S"(crc)
+                        :"0"(crc), "c"(*ptmp)
+                );
+                ptmp++;
+        }
+
+        if (iremainder)
+                crc = btrfs_crc32c_le_hw_byte(crc, (unsigned char *)ptmp,
+                                              iremainder);
+
+        return crc;
+}
+#endif /* CONFIG_BTRFS_HW_SUM */
+
+static inline u32 __btrfs_crc32c(u32 crc, unsigned char const *address,
+                                 size_t len)
+{
+#ifdef CONFIG_BTRFS_HW_SUM
+        if (cpu_has_xmm4_2)
+                return btrfs_crc32c_le_hw(crc, address, len);
+#endif
+        return crc32c_le(crc, address, len);
+}
+
+#else
+
+#define __btrfs_crc32c(seed, data, length) crc32c(seed, data, length)
+
+#endif /* CONFIG_X86 */
+
 /**
  * implementation of crc32c_le() changed in linux-2.6.23,
  * has of v0.13 btrfs-progs is using the latest version.
@@ -10,8 +98,11 @@
  */
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,23)
 #define btrfs_crc32c(seed, data, length) \
-        __cpu_to_le32( crc32c( __le32_to_cpu(seed), data, length) )
+        __cpu_to_le32( __btrfs_crc32c( __le32_to_cpu(seed), \
+                                      (unsigned char const *)data, length) )
 #else
 #define btrfs_crc32c(seed, data, length) \
-        crc32c(seed, data, length)
+        __btrfs_crc32c(seed, (unsigned char const *)data, length)
+#endif
 #endif
+