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-rw-r--r--arch/x86/lib/csum-partial_64.c199
1 files changed, 87 insertions, 112 deletions
diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
index 9845371c5c36..c9dae65ac01b 100644
--- a/arch/x86/lib/csum-partial_64.c
+++ b/arch/x86/lib/csum-partial_64.c
@@ -1,140 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
/*
* arch/x86_64/lib/csum-partial.c
*
* This file contains network checksum routines that are better done
* in an architecture-specific manner due to speed.
*/
-
+
#include <linux/compiler.h>
-#include <linux/module.h>
+#include <linux/export.h>
#include <asm/checksum.h>
+#include <asm/word-at-a-time.h>
+
+static inline __wsum csum_finalize_sum(u64 temp64)
+{
+ return (__force __wsum)((temp64 + ror64(temp64, 32)) >> 32);
+}
-static inline unsigned short from32to16(unsigned a)
+static inline unsigned long update_csum_40b(unsigned long sum, const unsigned long m[5])
{
- unsigned short b = a >> 16;
- asm("addw %w2,%w0\n\t"
- "adcw $0,%w0\n"
- : "=r" (b)
- : "0" (b), "r" (a));
- return b;
+ asm("addq %1,%0\n\t"
+ "adcq %2,%0\n\t"
+ "adcq %3,%0\n\t"
+ "adcq %4,%0\n\t"
+ "adcq %5,%0\n\t"
+ "adcq $0,%0"
+ :"+r" (sum)
+ :"m" (m[0]), "m" (m[1]), "m" (m[2]),
+ "m" (m[3]), "m" (m[4]));
+ return sum;
}
/*
- * Do a 64-bit checksum on an arbitrary memory area.
+ * Do a checksum on an arbitrary memory area.
* Returns a 32bit checksum.
*
* This isn't as time critical as it used to be because many NICs
* do hardware checksumming these days.
- *
- * Things tried and found to not make it faster:
- * Manual Prefetching
- * Unrolling to an 128 bytes inner loop.
- * Using interleaving with more registers to break the carry chains.
+ *
+ * Still, with CHECKSUM_COMPLETE this is called to compute
+ * checksums on IPv6 headers (40 bytes) and other small parts.
+ * it's best to have buff aligned on a 64-bit boundary
*/
-static unsigned do_csum(const unsigned char *buff, unsigned len)
+__wsum csum_partial(const void *buff, int len, __wsum sum)
{
- unsigned odd, count;
- unsigned long result = 0;
+ u64 temp64 = (__force u64)sum;
- if (unlikely(len == 0))
- return result;
- odd = 1 & (unsigned long) buff;
- if (unlikely(odd)) {
- result = *buff << 8;
- len--;
- buff++;
- }
- count = len >> 1; /* nr of 16-bit words.. */
- if (count) {
- if (2 & (unsigned long) buff) {
- result += *(unsigned short *)buff;
- count--;
- len -= 2;
- buff += 2;
- }
- count >>= 1; /* nr of 32-bit words.. */
- if (count) {
- unsigned long zero;
- unsigned count64;
- if (4 & (unsigned long) buff) {
- result += *(unsigned int *) buff;
- count--;
- len -= 4;
- buff += 4;
- }
- count >>= 1; /* nr of 64-bit words.. */
+ /* Do two 40-byte chunks in parallel to get better ILP */
+ if (likely(len >= 80)) {
+ u64 temp64_2 = 0;
+ do {
+ temp64 = update_csum_40b(temp64, buff);
+ temp64_2 = update_csum_40b(temp64_2, buff + 40);
+ buff += 80;
+ len -= 80;
+ } while (len >= 80);
- /* main loop using 64byte blocks */
- zero = 0;
- count64 = count >> 3;
- while (count64) {
- asm("addq 0*8(%[src]),%[res]\n\t"
- "adcq 1*8(%[src]),%[res]\n\t"
- "adcq 2*8(%[src]),%[res]\n\t"
- "adcq 3*8(%[src]),%[res]\n\t"
- "adcq 4*8(%[src]),%[res]\n\t"
- "adcq 5*8(%[src]),%[res]\n\t"
- "adcq 6*8(%[src]),%[res]\n\t"
- "adcq 7*8(%[src]),%[res]\n\t"
- "adcq %[zero],%[res]"
- : [res] "=r" (result)
- : [src] "r" (buff), [zero] "r" (zero),
- "[res]" (result));
- buff += 64;
- count64--;
- }
+ asm("addq %1,%0\n\t"
+ "adcq $0,%0"
+ :"+r" (temp64): "r" (temp64_2));
+ }
- /* last up to 7 8byte blocks */
- count %= 8;
- while (count) {
- asm("addq %1,%0\n\t"
- "adcq %2,%0\n"
- : "=r" (result)
- : "m" (*(unsigned long *)buff),
- "r" (zero), "0" (result));
- --count;
- buff += 8;
- }
- result = add32_with_carry(result>>32,
- result&0xffffffff);
+ /*
+ * len == 40 is the hot case due to IPv6 headers, so return
+ * early for that exact case without checking the tail bytes.
+ */
+ if (len >= 40) {
+ temp64 = update_csum_40b(temp64, buff);
+ len -= 40;
+ if (!len)
+ return csum_finalize_sum(temp64);
+ buff += 40;
+ }
- if (len & 4) {
- result += *(unsigned int *) buff;
- buff += 4;
- }
- }
- if (len & 2) {
- result += *(unsigned short *) buff;
- buff += 2;
- }
+ if (len & 32) {
+ asm("addq 0*8(%[src]),%[res]\n\t"
+ "adcq 1*8(%[src]),%[res]\n\t"
+ "adcq 2*8(%[src]),%[res]\n\t"
+ "adcq 3*8(%[src]),%[res]\n\t"
+ "adcq $0,%[res]"
+ : [res] "+r"(temp64)
+ : [src] "r"(buff), "m"(*(const char(*)[32])buff));
+ buff += 32;
}
- if (len & 1)
- result += *buff;
- result = add32_with_carry(result>>32, result & 0xffffffff);
- if (unlikely(odd)) {
- result = from32to16(result);
- result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+ if (len & 16) {
+ asm("addq 0*8(%[src]),%[res]\n\t"
+ "adcq 1*8(%[src]),%[res]\n\t"
+ "adcq $0,%[res]"
+ : [res] "+r"(temp64)
+ : [src] "r"(buff), "m"(*(const char(*)[16])buff));
+ buff += 16;
}
- return result;
-}
+ if (len & 8) {
+ asm("addq 0*8(%[src]),%[res]\n\t"
+ "adcq $0,%[res]"
+ : [res] "+r"(temp64)
+ : [src] "r"(buff), "m"(*(const char(*)[8])buff));
+ buff += 8;
+ }
+ if (len & 7) {
+ unsigned int shift = (-len << 3) & 63;
+ unsigned long trail;
-/*
- * computes the checksum of a memory block at buff, length len,
- * and adds in "sum" (32-bit)
- *
- * returns a 32-bit number suitable for feeding into itself
- * or csum_tcpudp_magic
- *
- * this function must be called with even lengths, except
- * for the last fragment, which may be odd
- *
- * it's best to have buff aligned on a 64-bit boundary
- */
-__wsum csum_partial(const void *buff, int len, __wsum sum)
-{
- return (__force __wsum)add32_with_carry(do_csum(buff, len),
- (__force u32)sum);
+ trail = (load_unaligned_zeropad(buff) << shift) >> shift;
+
+ asm("addq %[trail],%[res]\n\t"
+ "adcq $0,%[res]"
+ : [res] "+r"(temp64)
+ : [trail] "r"(trail));
+ }
+ return csum_finalize_sum(temp64);
}
+EXPORT_SYMBOL(csum_partial);
/*
* this routine is used for miscellaneous IP-like checksums, mainly
@@ -142,7 +118,6 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
*/
__sum16 ip_compute_csum(const void *buff, int len)
{
- return csum_fold(csum_partial(buff,len,0));
+ return csum_fold(csum_partial(buff, len, 0));
}
EXPORT_SYMBOL(ip_compute_csum);
-
generated by cgit (git 2.34.1) at 2025-12-25 03:42:12 +0000