linux-kernel - [PATCH v3] RISC-V: KVM: Remove scounteren initialization

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Message-Id: <20250515-fix_scounteren_vs-v3-1-729dc088943e@rivosinc.com>
Date: Thu, 15 May 2025 16:11:18 -0700
From: Atish Patra <atishp@...osinc.com>
To: Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Alexandre Ghiti <alex@...ti.fr>
Cc: kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Atish Patra <atishp@...osinc.com>
Subject: [PATCH v3] 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@...osinc.com>
---
Changes in v3:
- Removed the redundant declaration 
- Link to v2: https://lore.kernel.org/r/20250515-fix_scounteren_vs-v2-1-1fd8dc0693e8@rivosinc.com

Changes in v2:
- Remove the scounteren initialization instead of just setting the TM bit. 
- Link to v1: https://lore.kernel.org/r/20250513-fix_scounteren_vs-v1-1-c1f52af93c79@rivosinc.com
---
 arch/riscv/kvm/vcpu.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 60d684c76c58..9bfaae9a11ea 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -111,7 +111,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 {
 	int rc;
 	struct kvm_cpu_context *cntx;
-	struct kvm_vcpu_csr *reset_csr = &vcpu->arch.guest_reset_csr;
 
 	spin_lock_init(&vcpu->arch.mp_state_lock);
 
@@ -146,9 +145,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	if (kvm_riscv_vcpu_alloc_vector_context(vcpu, cntx))
 		return -ENOMEM;
 
-	/* 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);
 

---
base-commit: 01f95500a162fca88cefab9ed64ceded5afabc12
change-id: 20250513-fix_scounteren_vs-fdd86255c7b7
--
Regards,
Atish patra