Commit 5bc40978 authored May 15, 2025 by Atish Patra Committed by Anup Patel May 21, 2025

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 <atishp@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20250515-fix_scounteren_vs-v3-1-729dc088943e@rivosinc.com


Signed-off-by: Anup Patel <anup@brainfault.org>

parent 9f0e6b98

arch/riscv/kernel/head.S

+10 −0

Original line number	Diff line number	Diff line
		@@ -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

+0 −3

Original line number	Diff line number	Diff line
		@@ -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)