linux-kernel - [PATCH] KVM: arm64: nv: Forward hvc traps if originated from nested VM

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Message-ID: <20250410070743.1072583-1-gankulkarni@os.amperecomputing.com>
Date: Thu, 10 Apr 2025 00:07:43 -0700
From: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
To: linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Cc: maz@...nel.org,
	oliver.upton@...ux.dev,
	joey.gouly@....com,
	suzuki.poulose@....com,
	yuzenghui@...wei.com,
	darren@...amperecomputing.com,
	gankulkarni@...amperecomputing.com
Subject: [PATCH] KVM: arm64: nv: Forward hvc traps if originated from nested VM

It was discovered while trying selftest(smccc_filter) that the
hvc trap is getting forwarded to guest hypervisor even if it is
originated from itself.

HVC traps from guest hypervisor should be handled by the host
hypervisor and traps originating from nested VM should be
forwarded. Adding check to forward only if the hvc is trapped
from the nested VM.

Signed-off-by: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
---
 arch/arm64/kvm/handle_exit.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 80218f62773b..894f92693ed9 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -40,8 +40,8 @@ static int handle_hvc(struct kvm_vcpu *vcpu)
 			    kvm_vcpu_hvc_get_imm(vcpu));
 	vcpu->stat.hvc_exit_stat++;
 
-	/* Forward hvc instructions to the virtual EL2 if the guest has EL2. */
-	if (vcpu_has_nv(vcpu)) {
+	/* Forward hvc instructions to the virtual EL2, if it is from nested VM. */
+	if (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)) {
 		if (vcpu_read_sys_reg(vcpu, HCR_EL2) & HCR_HCD)
 			kvm_inject_undefined(vcpu);
 		else
-- 
2.48.1