From: Shubing Guo <guo.shubing@zte.com.cn>
Date: Tue, 1 Jul 2025 02:36:50 +0000 (+0800)
Subject: vppinfra: fix cpu time on riscv
X-Git-Tag: v26.02-rc0~112
X-Git-Url: https://gerrit.fd.io/r/gitweb?a=commitdiff_plain;h=refs%2Fchanges%2F77%2F43377%2F3;p=vpp.git

vppinfra: fix cpu time on riscv

Starting with Linux 6.6 [1], RDCYCLE is a privileged instruction on
RISC-V and can't be used directly from userland.Use RDTIME instead,
which while less accurate has the advantage of being synchronized
between CPU (and thus monotonic) and of constant frequency.

Type: fix
Change-Id: I53ab9cd1d0fcdd8f0e88d189840ba1d3b5ddd67a
Signed-off-by: Shubing Guo <guo.shubing@zte.com.cn>
---

diff --git a/src/vppinfra/time.h b/src/vppinfra/time.h
index 761dbed3fe8..05e82f8895f 100644
--- a/src/vppinfra/time.h
+++ b/src/vppinfra/time.h
@@ -192,13 +192,13 @@ clib_cpu_time_now (void)
   return result;
 }
 
-#elif defined(__riscv)
+#elif defined(__riscv) && defined(__riscv_xlen) && (__riscv_xlen == 64)
 
 always_inline u64
 clib_cpu_time_now (void)
 {
   u64 result;
-  asm volatile("rdcycle %0\n" : "=r"(result));
+  asm volatile ("rdtime %0\n" : "=r"(result));
   return result;
 }
 #else