linux-kernel - Re: [PATCH 00/67] KVM: iommu: Overhaul device posted IRQs support

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Message-ID: <CALzav=dMSLy7kt6sJtRqAK8tOZwFz9Ktp3vzqggdD+J_aPVycg@mail.gmail.com>
Date: Tue, 8 Apr 2025 10:13:05 -0700
From: David Matlack <dmatlack@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Joerg Roedel <joro@...tes.org>, 
	David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>, kvm@...r.kernel.org, 
	iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Maxim Levitsky <mlevitsk@...hat.com>, Joao Martins <joao.m.martins@...cle.com>
Subject: Re: [PATCH 00/67] KVM: iommu: Overhaul device posted IRQs support

On Fri, Apr 4, 2025 at 12:39 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> This series is well tested except for one notable gap: I was not able to
> fully test the AMD IOMMU changes.  Long story short, getting upstream
> kernels into our full test environments is practically infeasible.  And
> exposing a device or VF on systems that are available to developers is a
> bit of a mess.
>
> The device the selftest (see the last patch) uses is an internel test VF
> that's hosted on a smart NIC using non-production (test-only) firmware.
> Unfortunately, only some of our developer systems have the right NIC, and
> for unknown reasons I couldn't get the test firmware to install cleanly on
> Rome systems.  I was able to get it functional on Milan (and Intel CPUs),
> but APIC virtualization is disabled on Milan.  Thanks to KVM's force_avic
> I could test the KVM flows, but the IOMMU was having none of my attempts
> to force enable APIC virtualization against its will.

(Sean already knows this but just sharing for the broader visibility.)

I am working on a VFIO selftests framework and helper library that we
can link into the KVM selftests to make this kind of testing much
easier. It will support a driver framework so we can support testing
against different devices in a common way. Developers/companies can
carry their own out-of-tree drivers for non-standard/custom test
devices, e.g. the "Mercury device" used in this series.

I will send an RFC in the coming weeks. If/when my proposal is merged,
then I think we'll have a clean way to get the vfio_irq_test merged
upstream as well.