From: Marc Zyngier <maz@kernel•org>
To: kvmarm@lists•linux.dev, linux-arm-kernel@lists•infradead.org,
kvm@vger•kernel.org
Cc: Steffen Eiden <seiden@linux•ibm.com>,
Joey Gouly <joey.gouly@arm•com>,
Suzuki K Poulose <suzuki.poulose@arm•com>,
Oliver Upton <oupton@kernel•org>,
Zenghui Yu <yuzenghui@huawei•com>,
Mark Rutland <mark.rutland@arm•com>,
Will Deacon <will@kernel•org>, Fuad Tabba <tabba@google•com>
Subject: [PATCH 1/2] KVM: arm64: nv: Track L2 to L1 exception emulation
Date: Tue, 12 May 2026 15:07:54 +0100 [thread overview]
Message-ID: <20260512140755.3676306-2-maz@kernel.org> (raw)
In-Reply-To: <20260512140755.3676306-1-maz@kernel.org>
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 <maz@kernel•org>
---
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
next prev parent reply other threads:[~2026-05-12 14:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 14:07 [PATCH 0/2] KVM: arm64: nv: Reduce FP/SVE overhead on exception/exception return Marc Zyngier
2026-05-12 14:07 ` Marc Zyngier [this message]
2026-05-12 14:07 ` [PATCH 2/2] KVM: arm64: nv: Don't save/restore FP register during a nested ERET or exception Marc Zyngier
2026-05-13 12:28 ` Mark Rutland
2026-05-13 12:49 ` Marc Zyngier
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