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From: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
To: dev@dpdk.org
Date: Mon, 7 Sep 2020 22:40:08 +0100
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Subject: [dpdk-dev] [PATCH v2 17/41] pipeline: introduce SWX cksub
instruction
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The cksub (i.e. checksum subtract) instruction is used to update the
1's complement sum commonly used by protocols such as IPv4, TCP or
UDP.
Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
---
lib/librte_pipeline/rte_swx_pipeline.c | 116 +++++++++++++++++++++++++
1 file changed, 116 insertions(+)
diff --git a/lib/librte_pipeline/rte_swx_pipeline.c b/lib/librte_pipeline/rte_swx_pipeline.c
index 96e6c98aa..364c7d75a 100644
--- a/lib/librte_pipeline/rte_swx_pipeline.c
+++ b/lib/librte_pipeline/rte_swx_pipeline.c
@@ -297,6 +297,12 @@ enum instruction_type {
INSTR_ALU_CKADD_FIELD, /* src = H */
INSTR_ALU_CKADD_STRUCT20, /* src = h.header, with sizeof(header) = 20 */
INSTR_ALU_CKADD_STRUCT, /* src = h.hdeader, with any sizeof(header) */
+
+ /* cksub dst src
+ * dst = dst '- src
+ * dst = H, src = H
+ */
+ INSTR_ALU_CKSUB_FIELD,
};
struct instr_operand {
@@ -3034,6 +3040,36 @@ instr_alu_ckadd_translate(struct rte_swx_pipeline *p,
return 0;
}
+static int
+instr_alu_cksub_translate(struct rte_swx_pipeline *p,
+ struct action *action __rte_unused,
+ char **tokens,
+ int n_tokens,
+ struct instruction *instr,
+ struct instruction_data *data __rte_unused)
+{
+ char *dst = tokens[1], *src = tokens[2];
+ struct header *hdst, *hsrc;
+ struct field *fdst, *fsrc;
+
+ CHECK(n_tokens == 3, EINVAL);
+
+ fdst = header_field_parse(p, dst, &hdst);
+ CHECK(fdst && (fdst->n_bits == 16), EINVAL);
+
+ fsrc = header_field_parse(p, src, &hsrc);
+ CHECK(fsrc, EINVAL);
+
+ instr->type = INSTR_ALU_CKSUB_FIELD;
+ instr->alu.dst.struct_id = (uint8_t)hdst->struct_id;
+ instr->alu.dst.n_bits = fdst->n_bits;
+ instr->alu.dst.offset = fdst->offset / 8;
+ instr->alu.src.struct_id = (uint8_t)hsrc->struct_id;
+ instr->alu.src.n_bits = fsrc->n_bits;
+ instr->alu.src.offset = fsrc->offset / 8;
+ return 0;
+}
+
static inline void
instr_alu_add_exec(struct rte_swx_pipeline *p)
{
@@ -3273,6 +3309,77 @@ instr_alu_ckadd_field_exec(struct rte_swx_pipeline *p)
thread_ip_inc(p);
}
+static inline void
+instr_alu_cksub_field_exec(struct rte_swx_pipeline *p)
+{
+ struct thread *t = &p->threads[p->thread_id];
+ struct instruction *ip = t->ip;
+ uint8_t *dst_struct, *src_struct;
+ uint16_t *dst16_ptr, dst;
+ uint64_t *src64_ptr, src64, src64_mask, src;
+ uint64_t r;
+
+ TRACE("[Thread %2u] cksub (field)\n", p->thread_id);
+
+ /* Structs. */
+ dst_struct = t->structs[ip->alu.dst.struct_id];
+ dst16_ptr = (uint16_t *)&dst_struct[ip->alu.dst.offset];
+ dst = *dst16_ptr;
+
+ src_struct = t->structs[ip->alu.src.struct_id];
+ src64_ptr = (uint64_t *)&src_struct[ip->alu.src.offset];
+ src64 = *src64_ptr;
+ src64_mask = UINT64_MAX >> (64 - ip->alu.src.n_bits);
+ src = src64 & src64_mask;
+
+ r = dst;
+ r = ~r & 0xFFFF;
+
+ /* Subtraction in 1's complement arithmetic (i.e. a '- b) is the same as
+ * the following sequence of operations in 2's complement arithmetic:
+ * a '- b = (a - b) % 0xFFFF.
+ *
+ * In order to prevent an underflow for the below subtraction, in which
+ * a 33-bit number (the subtrahend) is taken out of a 16-bit number (the
+ * minuend), we first add a multiple of the 0xFFFF modulus to the
+ * minuend. The number we add to the minuend needs to be a 34-bit number
+ * or higher, so for readability reasons we picked the 36-bit multiple.
+ * We are effectively turning the 16-bit minuend into a 36-bit number:
+ * (a - b) % 0xFFFF = (a + 0xFFFF00000 - b) % 0xFFFF.
+ */
+ r += 0xFFFF00000ULL; /* The output r is a 36-bit number. */
+
+ /* A 33-bit number is subtracted from a 36-bit number (the input r). The
+ * result (the output r) is a 36-bit number.
+ */
+ r -= (src >> 32) + (src & 0xFFFFFFFF);
+
+ /* The first input is a 16-bit number. The second input is a 20-bit
+ * number. Their sum is a 21-bit number.
+ */
+ r = (r & 0xFFFF) + (r >> 16);
+
+ /* The first input is a 16-bit number (0 .. 0xFFFF). The second input is
+ * a 5-bit number (0 .. 31). The sum is a 17-bit number (0 .. 0x1001E).
+ */
+ r = (r & 0xFFFF) + (r >> 16);
+
+ /* When the input r is (0 .. 0xFFFF), the output r is equal to the input
+ * r, so the output is (0 .. 0xFFFF). When the input r is (0x10000 ..
+ * 0x1001E), the output r is (0 .. 31). So no carry bit can be
+ * generated, therefore the output r is always a 16-bit number.
+ */
+ r = (r & 0xFFFF) + (r >> 16);
+
+ r = ~r & 0xFFFF;
+ r = r ? r : 0xFFFF;
+
+ *dst16_ptr = (uint16_t)r;
+
+ /* Thread. */
+ thread_ip_inc(p);
+}
+
static inline void
instr_alu_ckadd_struct20_exec(struct rte_swx_pipeline *p)
{
@@ -3502,6 +3609,14 @@ instr_translate(struct rte_swx_pipeline *p,
instr,
data);
+ if (!strcmp(tokens[tpos], "cksub"))
+ return instr_alu_cksub_translate(p,
+ action,
+ &tokens[tpos],
+ n_tokens - tpos,
+ instr,
+ data);
+
CHECK(0, EINVAL);
}
@@ -3677,6 +3792,7 @@ static instr_exec_t instruction_table[] = {
[INSTR_ALU_CKADD_FIELD] = instr_alu_ckadd_field_exec,
[INSTR_ALU_CKADD_STRUCT] = instr_alu_ckadd_struct_exec,
[INSTR_ALU_CKADD_STRUCT20] = instr_alu_ckadd_struct20_exec,
+ [INSTR_ALU_CKSUB_FIELD] = instr_alu_cksub_field_exec,
};
static inline void
--
2.17.1