From: Vincent Donnefort <vdonnefort@google•com>
To: maz@kernel•org, oliver.upton@linux•dev, joey.gouly@arm•com,
suzuki.poulose@arm•com, yuzenghui@huawei•com,
catalin.marinas@arm•com, will@kernel•org
Cc: linux-arm-kernel@lists•infradead.org, kvmarm@lists•linux.dev,
kernel-team@android•com, tabba@google•com,
Vincent Donnefort <vdonnefort@google•com>
Subject: [PATCH] KVM: arm64: Set a linux errno on SMCCC error in kvm_call_hyp_nvhe()
Date: Wed, 3 Jun 2026 12:03:12 +0100 [thread overview]
Message-ID: <20260603110312.2909844-1-vdonnefort@google.com> (raw)
If the HVC called in kvm_call_hyp_nvhe() fails with an SMCCC error code,
we WARN. However, the returned value isn't initialized and the caller
might get garbage or 0 which is likely to be interpreted as success.
Set a default -EPERM error value, ensuring all callers get the message
when SMCCC calls fail.
Signed-off-by: Vincent Donnefort <vdonnefort@google•com>
---
I have encountered this issue while working on a follow-up contribution to the
hypervisor tracing. In that case it completely crashed the kernel because
IS_ERR() failed on that res.a1 value.
Now, if it makes that function more robust, I do not believe it is fixing any
existing bug which is why I haven't added a "Fixes:" tag.
In case we want to stick one, here it is:
Fixes: 054698316d87 ("KVM: arm64: nVHE: Migrate hyp interface to SMCCC")
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a49042bfa801..6b8fd494792c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1273,13 +1273,14 @@ void kvm_arm_resume_guest(struct kvm *kvm);
#define vcpu_has_run_once(vcpu) (!!READ_ONCE((vcpu)->pid))
#ifndef __KVM_NVHE_HYPERVISOR__
-#define kvm_call_hyp_nvhe(f, ...) \
+#define kvm_call_hyp_nvhe(f, ...) \
({ \
struct arm_smccc_res res; \
\
arm_smccc_1_1_hvc(KVM_HOST_SMCCC_FUNC(f), \
##__VA_ARGS__, &res); \
- WARN_ON(res.a0 != SMCCC_RET_SUCCESS); \
+ if (WARN_ON(res.a0 != SMCCC_RET_SUCCESS)) \
+ res.a1 = -EPERM; \
\
res.a1; \
})
base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
--
2.54.0.1032.g2f8565e1d1-goog
next reply other threads:[~2026-06-03 11:03 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-03 11:03 Vincent Donnefort [this message]
2026-06-03 11:22 ` [PATCH] KVM: arm64: Set a linux errno on SMCCC error in kvm_call_hyp_nvhe() Fuad Tabba
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