linux-kernel - [PATCH] RISC-V: KVM: make CY, TM, and IR counters accessible in VU mode

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Date:   Mon, 31 Jan 2022 16:33:07 +0530
From:   Mayuresh Chitale <mchitale@...tanamicro.com>
To:     anup@...infault.org
Cc:     atishp@...shpatra.org, palmer@...belt.com,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Mayuresh Chitale <mchitale@...tanamicro.com>
Subject: [PATCH] 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: a33c72faf2d73 ("RISC-V: KVM: Implement VCPU create, init and
destroy functions")
Cc:stable@...r.kernel.org
Signed-off-by: Mayuresh Chitale <mchitale@...tanamicro.com>
---
 arch/riscv/kvm/vcpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 0c5239e05721..caaf824347b9 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/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);
 
-- 
2.25.1