[v1, 6/6] riscv: vector: enable preemptive kernel-mode Vector to be built

[Andy Chiu]

Add a Kconfig to let user decides whether kernel-mode Vector in a
preemptive kernel should also run with preemption. If the config is 'N',
then all kernel-mode Vector code are run with preemption disabled.

Signed-off-by: Andy Chiu <andy.chiu at sifive.com>
---
 arch/riscv/Kconfig | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a9e8b697fefb..da6a45ea42ec 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -500,6 +500,16 @@ config RISCV_ISA_V_DEFAULT_ENABLE
 
 	  If you don't know what to do here, say Y.
 
+config RISCV_ISA_V_PREEMPTIVE_KMV
+	bool "Run kernel-mode Vector with kernel preemption"
+	depends on PREEMPTION
+	depends on RISCV_ISA_V
+	default y
+	help
+	  Ordinarily the kernel disables preemption before running in-kernel
+	  Vector code. This config frees the kernel from disabling preemption
+	  by adding meory on demand for tracking kernel's V-context.
+
 config TOOLCHAIN_HAS_ZBB
 	bool
 	default y
-- 
2.17.1