[incubator-nuttx] branch master updated: arch: qemu-rv: Fix high CPU usage in SMP mode

[pk...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

pkarashchenko pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 548540eb13 arch: qemu-rv: Fix high CPU usage in SMP mode
548540eb13 is described below

commit 548540eb13345e4cca9af7b25daae94fa6374fe2
Author: Masayuki Ishikawa <ma...@gmail.com>
AuthorDate: Sat Aug 13 22:33:52 2022 +0900

    arch: qemu-rv: Fix high CPU usage in SMP mode
    
    Summary:
    - I noticed that QEMU shows high CPU usage if the number of
      CPUs does not match the kernel configuration. (e.g. -smp 8
      and CONFIG_SMP_NCPUS=2)
    - This commit fixes this issue.
    
    Impact:
    - qemu-rv only
    
    Testing:
    - Tested with the following configs
      - rv-virt:smp64 (CONFIG_NCPUS=1/2/8)
      - rv-virt:nsh64
    
    Signed-off-by: Masayuki Ishikawa <Ma...@jp.sony.com>
---
 arch/risc-v/src/qemu-rv/qemu_rv_head.S | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/risc-v/src/qemu-rv/qemu_rv_head.S b/arch/risc-v/src/qemu-rv/qemu_rv_head.S
index ebfe5d1c68..f55ec9a30b 100644
--- a/arch/risc-v/src/qemu-rv/qemu_rv_head.S
+++ b/arch/risc-v/src/qemu-rv/qemu_rv_head.S
@@ -52,13 +52,21 @@ __start:
   j    2f
 1:
 
-  /* In case of single CPU config, stop here */
+  /* Load the number of CPUs that the kernel supports */
 
-#if !defined(CONFIG_SMP) || (CONFIG_SMP_NCPUS == 1)
+#ifdef CONFIG_SMP
+  li   t1, CONFIG_SMP_NCPUS
+#else
+  li   t1, 1
+#endif
+
+  /* If a0 (mhartid) >= t1 (the number of CPUs), stop here */
+
+  blt  a0, t1, 3f
   csrw mie, zero
   wfi
-#endif
 
+3:
   /* To get g_cpu_basestack[mhartid], must get g_cpu_basestack first */
 
   la   t0, g_cpu_basestack