linux-kernel - [PATCH v2 2/6] KVM: arm64: Set FnV for VCPU when FAR

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Message-ID: <20250604050902.3944054-3-jiaqiyan@google.com>
Date: Wed,  4 Jun 2025 05:08:57 +0000
From: Jiaqi Yan <jiaqiyan@...gle.com>
To: maz@...nel.org, oliver.upton@...ux.dev
Cc: joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com, 
	catalin.marinas@....com, will@...nel.org, pbonzini@...hat.com, corbet@....net, 
	shuah@...nel.org, kvm@...r.kernel.org, kvmarm@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	duenwen@...gle.com, rananta@...gle.com, jthoughton@...gle.com, 
	Jiaqi Yan <jiaqiyan@...gle.com>
Subject: [PATCH v2 2/6] KVM: arm64: Set FnV for VCPU when FAR_EL2 is invalid

Certain microarchitectures (e.g. Neoverse V2) do not keep track of
the faulting address for a memory load that consumes poisoned data
and results in a synchronous external abort (SEA). IOW, both
FAR_EL2 register and kvm_vcpu_get_hfar holds a garbage value.

In case VMM later totally relies on KVM to synchronously inject a
SEA into the guest, KVM should set FnV bit in VCPU's
- ESR_EL1 to let guest kernel know FAR_EL1 is invalid
- ESR_EL2 to let nested virtualization know FAR_EL2 is invalid

Signed-off-by: Jiaqi Yan <jiaqiyan@...gle.com>
---
 arch/arm64/kvm/inject_fault.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index a640e839848e6..b4f9a09952ead 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -81,6 +81,9 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
 	if (!is_iabt)
 		esr |= ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT;
 
+	if (!kvm_vcpu_sea_far_valid(vcpu))
+		esr |= ESR_ELx_FnV;
+
 	esr |= ESR_ELx_FSC_EXTABT;
 
 	if (match_target_el(vcpu, unpack_vcpu_flag(EXCEPT_AA64_EL1_SYNC))) {
-- 
2.49.0.1266.g31b7d2e469-goog