RISC-V: KVM: Remove scounteren initialization

Scounteren CSR controls the direct access the hpmcounters and cycle/
instret/time from the userspace. It's the supervisor's responsibility
to set it up correctly for it's user space. They hypervisor doesn't
need to decide the policy on behalf of the supervisor.

Signed-off-by: Atish Patra <[email protected]>
Reviewed-by: Andrew Jones <[email protected]>
Reviewed-by: Anup Patel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Anup Patel <[email protected]>

Author: atishp04

arch/riscv/kernel/head.S

@@ -131,6 +131,12 @@ secondary_start_sbi:
 	csrw CSR_IE, zero
 	csrw CSR_IP, zero
 
+#ifndef CONFIG_RISCV_M_MODE
+	/* Enable time CSR */
+	li t0, 0x2
+	csrw CSR_SCOUNTEREN, t0
+#endif
+
 	/* Load the global pointer */
 	load_global_pointer
 
@@ -226,6 +232,10 @@ SYM_CODE_START(_start_kernel)
 	 * to hand it to us.
 	 */
 	csrr a0, CSR_MHARTID
+#else
+	/* Enable time CSR */
+	li t0, 0x2
+	csrw CSR_SCOUNTEREN, t0
 #endif /* CONFIG_RISCV_M_MODE */
 
 	/* Load the global pointer */

arch/riscv/kvm/vcpu.c

@@ -79,9 +79,6 @@ static void kvm_riscv_vcpu_context_reset(struct kvm_vcpu *vcpu)
 	cntx->hstatus |= HSTATUS_VTW;
 	cntx->hstatus |= HSTATUS_SPVP;
 	cntx->hstatus |= HSTATUS_SPV;
-
-	/* By default, make CY, TM, and IR counters accessible in VU mode */
-	csr->scounteren = 0x7;
 }
 
 static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)