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arch: qemu-rv: Fix high CPU usage in SMP mode

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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 <Masayuki.Ishikawa@jp.sony.com>
This commit is contained in:
Masayuki Ishikawa 2022-08-13 22:33:52 +09:00 committed by Xiang Xiao
parent 00296c1ef3
commit d32555f3e0
1 changed files with 12 additions and 4 deletions
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16
arch/risc-v/src/qemu-rv/qemu_rv_head.S
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@ -52,13 +52,21 @@ __start:
j 2f j 2f
1: 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
csrw mie, zero li t1, CONFIG_SMP_NCPUS
wfi #else
li t1, 1
#endif #endif
/* If a0 (mhartid) >= t1 (the number of CPUs), stop here */
blt a0, t1, 3f
csrw mie, zero
wfi
3:
/* To get g_cpu_basestack[mhartid], must get g_cpu_basestack first */ /* To get g_cpu_basestack[mhartid], must get g_cpu_basestack first */
la t0, g_cpu_basestack la t0, g_cpu_basestack