[PATCH v3 2/2] RISC-V: KVM: Redirect illegal instruction traps to guest

[Anup Patel]

From: Andy Chiu <andy.chiu at sifive.com>

The M-mode redirects an unhandled illegal instruction trap back
to S-mode. However, KVM running in HS-mode terminates the VS-mode
software when it receives illegal instruction trap. Instead, KVM
should redirect the illegal instruction trap back to VS-mode, and
let VS-mode trap handler decide the next step. This futher allows
guest kernel to implement on-demand enabling of vector extension
for a guest user space process upon first-use.

Signed-off-by: Andy Chiu <andy.chiu at sifive.com>
Signed-off-by: Anup Patel <apatel at ventanamicro.com>
Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
---
 arch/riscv/kvm/vcpu_exit.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
index af7c4bc07929..4ea101a73d8b 100644
--- a/arch/riscv/kvm/vcpu_exit.c
+++ b/arch/riscv/kvm/vcpu_exit.c
@@ -182,6 +182,12 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	ret = -EFAULT;
 	run->exit_reason = KVM_EXIT_UNKNOWN;
 	switch (trap->scause) {
+	case EXC_INST_ILLEGAL:
+		if (vcpu->arch.guest_context.hstatus & HSTATUS_SPV) {
+			kvm_riscv_vcpu_trap_redirect(vcpu, trap);
+			ret = 1;
+		}
+		break;
 	case EXC_VIRTUAL_INST_FAULT:
 		if (vcpu->arch.guest_context.hstatus & HSTATUS_SPV)
 			ret = kvm_riscv_vcpu_virtual_insn(vcpu, run, trap);
-- 
2.34.1