linux-kernel - [PATCH 20/27] RISC-V: KVM: Redirect nested WFI and WRS traps

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Message-ID: <20260120080013.2153519-21-anup.patel@oss.qualcomm.com>
Date: Tue, 20 Jan 2026 13:30:06 +0530
From: Anup Patel <anup.patel@....qualcomm.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Atish Patra <atish.patra@...ux.dev>
Cc: Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <pjw@...nel.org>,
        Alexandre Ghiti <alex@...ti.fr>, Shuah Khan <shuah@...nel.org>,
        Anup Patel <anup@...infault.org>,
        Andrew Jones <andrew.jones@....qualcomm.com>,
        kvm-riscv@...ts.infradead.org, kvm@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Anup Patel <anup.patel@....qualcomm.com>
Subject: [PATCH 20/27] RISC-V: KVM: Redirect nested WFI and WRS traps

The WFI and WRS virtual instruction traps from Guest VS/VU-mode
(aka L2/nested guest) should be redirected to Guest HS-mode (aka
L1/guest hypervisor).

Signed-off-by: Anup Patel <anup.patel@....qualcomm.com>
---
 arch/riscv/kvm/vcpu_insn.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
index 745cd654df94..ebd0cfc1bf30 100644
--- a/arch/riscv/kvm/vcpu_insn.c
+++ b/arch/riscv/kvm/vcpu_insn.c
@@ -76,6 +76,20 @@ void kvm_riscv_vcpu_wfi(struct kvm_vcpu *vcpu)
 
 static int wfi_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
 {
+	/*
+	 * Trap from virtual-VS/VU modes should be forwarded to
+	 * virtual-HS mode as a virtual instruction trap.
+	 */
+	if (kvm_riscv_vcpu_nested_virt(vcpu))
+		return KVM_INSN_VIRTUAL_TRAP;
+
+	/*
+	 * Trap from virtual-U mode should be forwarded to
+	 * virtual-HS mode as illegal instruction trap.
+	 */
+	if (!(vcpu->arch.guest_context.hstatus & HSTATUS_SPVP))
+		return KVM_INSN_ILLEGAL_TRAP;
+
 	vcpu->stat.wfi_exit_stat++;
 	kvm_riscv_vcpu_wfi(vcpu);
 	return KVM_INSN_CONTINUE_NEXT_SEPC;
@@ -83,6 +97,20 @@ static int wfi_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
 
 static int wrs_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
 {
+	/*
+	 * Trap from virtual-VS/VU modes should be forwarded to
+	 * virtual-HS mode as a virtual instruction trap.
+	 */
+	if (kvm_riscv_vcpu_nested_virt(vcpu))
+		return KVM_INSN_VIRTUAL_TRAP;
+
+	/*
+	 * Trap from virtual-U mode should be forwarded to
+	 * virtual-HS mode as illegal instruction trap.
+	 */
+	if (!(vcpu->arch.guest_context.hstatus & HSTATUS_SPVP))
+		return KVM_INSN_ILLEGAL_TRAP;
+
 	vcpu->stat.wrs_exit_stat++;
 	kvm_vcpu_on_spin(vcpu, vcpu->arch.guest_context.sstatus & SR_SPP);
 	return KVM_INSN_CONTINUE_NEXT_SEPC;
-- 
2.43.0