linux-kernel - Re: [RFC PATCH] KVM: arm/arm64: GICv4: Support shared VLPI

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Message-ID: <86edh228xx.wl-maz@kernel.org>
Date:   Mon, 06 Nov 2023 15:33:14 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Kunkun Jiang <jiangkunkun@...wei.com>
Cc:     Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Gavin Shan <gshan@...hat.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "open list:IRQCHIP DRIVERS" <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <kvmarm@...ts.linux.dev>,
        <wanghaibin.wang@...wei.com>
Subject: Re: [RFC PATCH] KVM: arm/arm64: GICv4: Support shared VLPI

On Mon, 06 Nov 2023 14:59:01 +0000,
Kunkun Jiang <jiangkunkun@...wei.com> wrote:
> 
> The virtio-pci driver write entry1-6
> massage.data in the msix-table and trap to QEMU for processing. The
> massage.data is as follow:
> > entry-0 0
> > entry-1 1
> > entry-2 1
> > entry-3 1
> > entry-4 1
> > entry-5 1
> > entry-6 1

Urgh... is vp_modern_queue_vector() used in your configuration? This
is ... terrible.

I wonder if PCIe actually allows this sort of thing.

In any case, this sort of behaviour breaks so many thing in KVM's
implementation that I'd recommend you disable GICv4 until we have a
good solution for that.

	M.

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