[ovs-dev] [PATCH v6 4/6] dpdk: enable cpu feature detection.

[Harry van Haaren]

This commit implements a method to retrieve the CPU ISA capabilities.
These ISA capabilities can be used in OVS to at runtime select a function
implementation to make the best use of the available ISA on the CPU.

Signed-off-by: Harry van Haaren <harry.van.haaren at intel.com>

---

v6:
- Add #if around RTE_CPUFLAG_AVX512F as it is not defined on CPU
  architectures that don't support the ISA. This check fixes compilation
  on those CPUs, as previously it had an undefined RTE_CPUFLAG_* error.
  (Reported by Travis, thanks Ian & William for running checks)

v5:
- Change API to return bool, and return to true/false (William Tu)
- Change error log to VLOG_ERR_ONCE instead of manual impl. (William Tu)

v4:
- Improve commit title and message
---
 lib/dpdk-stub.c |  9 +++++++++
 lib/dpdk.c      | 30 ++++++++++++++++++++++++++++++
 lib/dpdk.h      |  2 ++
 3 files changed, 41 insertions(+)

diff --git a/lib/dpdk-stub.c b/lib/dpdk-stub.c
index c332c217c..b7d577870 100644
--- a/lib/dpdk-stub.c
+++ b/lib/dpdk-stub.c
@@ -79,6 +79,15 @@ print_dpdk_version(void)
 {
 }
 
+bool
+dpdk_get_cpu_has_isa(const char *arch OVS_UNUSED,
+                     const char *feature OVS_UNUSED)
+{
+    VLOG_ERR_ONCE("DPDK not supported in this version of Open vSwitch, "
+                  "cannot use CPU flag based optimizations");
+    return false;
+}
+
 void
 dpdk_status(const struct ovsrec_open_vswitch *cfg)
 {
diff --git a/lib/dpdk.c b/lib/dpdk.c
index 31450d470..64a0d43e8 100644
--- a/lib/dpdk.c
+++ b/lib/dpdk.c
@@ -22,6 +22,7 @@
 #include <sys/stat.h>
 #include <getopt.h>
 
+#include <rte_cpuflags.h>
 #include <rte_errno.h>
 #include <rte_log.h>
 #include <rte_memzone.h>
@@ -513,6 +514,35 @@ print_dpdk_version(void)
     puts(rte_version());
 }
 
+#define CHECK_CPU_FEATURE(feature, name_str, RTE_CPUFLAG)               \
+    do {                                                                \
+        if (strncmp(feature, name_str, strlen(name_str)) == 0) {        \
+            int has_isa = rte_cpu_get_flag_enabled(RTE_CPUFLAG);        \
+            VLOG_DBG("CPU flag %s, available %s\n", name_str,           \
+                      has_isa ? "yes" : "no");                          \
+            return true;                                                \
+        }                                                               \
+    } while (0)
+
+bool
+dpdk_get_cpu_has_isa(const char *arch, const char *feature)
+{
+    /* Ensure Arch is x86_64 */
+    if (strncmp(arch, "x86_64", 6) != 0) {
+        return false;
+    }
+
+#if __x86_64__
+    /* CPU flags only defined for the architecture that support it */
+    CHECK_CPU_FEATURE(feature, "avx512f", RTE_CPUFLAG_AVX512F);
+    CHECK_CPU_FEATURE(feature, "bmi2", RTE_CPUFLAG_BMI2);
+#endif
+
+    VLOG_WARN("Unknown CPU arch,feature: %s,%s. Returning not supported.\n",
+              arch, feature);
+    return false;
+}
+
 void
 dpdk_status(const struct ovsrec_open_vswitch *cfg)
 {
diff --git a/lib/dpdk.h b/lib/dpdk.h
index 736a64279..445a51d06 100644
--- a/lib/dpdk.h
+++ b/lib/dpdk.h
@@ -44,4 +44,6 @@ bool dpdk_per_port_memory(void);
 bool dpdk_available(void);
 void print_dpdk_version(void);
 void dpdk_status(const struct ovsrec_open_vswitch *);
+bool dpdk_get_cpu_has_isa(const char *arch, const char *feature);
+
 #endif /* dpdk.h */
-- 
2.17.1