Subject: [PATCH 1/2] KVM: arm64: nv: Track L2 to L1 exception emulation

From: Marc Zyngier <[email-masked]>
Date: Tue, 12 May 2026 15:07:54 +0100

While we currently track that we are emulating a nested ERET from
L1 to L2, we currently don't track the reverse direction (an exception
going from L2 to L1).

Add a new vcpu state flag for this purpose, which will see some
use shortly.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/include/asm/kvm_host.h | 3 ++-
 arch/arm64/kvm/emulate-nested.c   | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 65eead8362e0b..c79747d5f4dd1 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1112,7 +1112,8 @@ struct kvm_vcpu_arch {
 #define IN_NESTED_ERET		__vcpu_single_flag(sflags, BIT(7))
 /* SError pending for nested guest */
 #define NESTED_SERROR_PENDING	__vcpu_single_flag(sflags, BIT(8))
-
+/* KVM is currently emulating an L2 to L1 exception */
+#define IN_NESTED_EXCEPTION	__vcpu_single_flag(sflags, BIT(9))
 
 /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
 #define vcpu_sve_pffr(vcpu) (kern_hyp_va((vcpu)->arch.sve_state) +	\
diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index dba7ced74ca5e..15c691a6266d5 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -2862,6 +2862,8 @@ static int kvm_inject_nested(struct kvm_vcpu *vcpu, u64 esr_el2,
 
 	preempt_disable();
 
+	vcpu_set_flag(vcpu, IN_NESTED_EXCEPTION);
+
 	/*
 	 * We may have an exception or PC update in the EL0/EL1 context.
 	 * Commit it before entering EL2.
@@ -2884,6 +2886,8 @@ static int kvm_inject_nested(struct kvm_vcpu *vcpu, u64 esr_el2,
 	__kvm_adjust_pc(vcpu);
 
 	kvm_arch_vcpu_load(vcpu, smp_processor_id());
+	vcpu_clear_flag(vcpu, IN_NESTED_EXCEPTION);
+
 	preempt_enable();
 
 	if (kvm_vcpu_has_pmu(vcpu))
-- 
2.47.3