RISC-V: KVM: make CY, TM, and IR counters accessible in VU mode

Those applications that run in VU mode and access the time CSR cause
a virtual instruction trap as Guest kernel currently does not
initialize the scounteren CSR.

To fix this, we should make CY, TM, and IR counters accessibile
by default in VU mode (similar to OpenSBI).

Fixes: a33c72f ("RISC-V: KVM: Implement VCPU create, init and
destroy functions")
Cc: [email protected]
Signed-off-by: Mayuresh Chitale <[email protected]>
Signed-off-by: Anup Patel <[email protected]>

Author: mdchitale

arch/riscv/kvm/vcpu.c

@@ -90,6 +90,7 @@ int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
 int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *cntx;
+	struct kvm_vcpu_csr *reset_csr = &vcpu->arch.guest_reset_csr;
 
 	/* Mark this VCPU never ran */
 	vcpu->arch.ran_atleast_once = false;
@@ -106,6 +107,9 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	cntx->hstatus |= HSTATUS_SPVP;
 	cntx->hstatus |= HSTATUS_SPV;
 
+	/* By default, make CY, TM, and IR counters accessible in VU mode */
+	reset_csr->scounteren = 0x7;
+
 	/* Setup VCPU timer */
 	kvm_riscv_vcpu_timer_init(vcpu);