linux-kernel - Re: [PATCH v3 02/62] KVM: arm64: WARN if unmapping vLPI fails

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Message-ID: <86tt4lcgs3.wl-maz@kernel.org>
Date: Thu, 12 Jun 2025 12:59:08 +0100
From: Marc Zyngier <maz@...nel.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Oliver Upton <oliver.upton@...ux.dev>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Joerg Roedel <joro@...tes.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Lu Baolu <baolu.lu@...ux.intel.com>,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	kvm@...r.kernel.org,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Sairaj Kodilkar <sarunkod@....com>,
	Vasant Hegde <vasant.hegde@....com>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	Joao Martins <joao.m.martins@...cle.com>,
	Francesco Lavra <francescolavra.fl@...il.com>,
	David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH v3 02/62] KVM: arm64: WARN if unmapping vLPI fails

On Wed, 11 Jun 2025 23:45:05 +0100,
Sean Christopherson <seanjc@...gle.com> wrote:
> 
> WARN if unmapping a vLPI in kvm_vgic_v4_unset_forwarding() fails, as
> failure means an IRTE has likely been left in a bad state, i.e. IRQs
> won't go where they should.

I have no idea what an IRTE is. But not having an VLPI mapping for an
interrupt at the point where we're tearing down the forwarding is
pretty benign. IRQs *still* go where they should, and we don't lose
anything.

What it may mean is that userspace and the guest may have done things
in the wrong order for KVM to accelerate interrupt delivery. That's
silly, but also completely harmless.

	M.


-- 
Without deviation from the norm, progress is not possible.