From: no-reply@sashiko.virtuozzo.com
To: devel@openvz.org, Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Subject: Re: [Devel] [PATCH hci-8.1 1/2] vfio: take the kvm reference only for drivers that read device->kvm
Date: Thu, 5 Nov 2026 12:23:01 +0000 [thread overview]
Message-ID: <010701a1aba99aaf-e4ecf006-1801-455a-acdf-b734bcc9ad40-000000@eu-central-1.amazonses.com> (raw)
In-Reply-To: <20261105121733.643754-2-andrey.drobyshev@virtuozzo.com>
> A device takes a reference to its group's kvm at the first open and
> drops it at the last close, so that device->kvm stays valid for the
> driver in between. QEMU's cpr-exec and cpr-transfer keep the device
> open while the VM is re-created, so the first VM stays referenced for
> as long as the device is: its vcpus, mm and in-kernel PIT thread with
> it. Seen as a second KVM instance in debugfs after a live update of a
> vGPU VM.
>
> Only three drivers read device->kvm after open_device(): KVMGT,
> vfio_ap and vfio-pci's zdev support. Let them say so with
> needs_kvm_ref, and take no reference for the others, which then can't
> keep a VM alive. Tested with nvidia-vgpu-vfio 595.71.03 on RTX 6000
> Ada SR-IOV VFs, a vfio-pci variant driver that doesn't read the
> pointer.
>
> Fixes: 2b48f52f2bff ("vfio: fix deadlock between group lock and kvm lock")
> https://virtuozzo.atlassian.net/browse/VSTOR-150597
> Feature: fix ms/vfio
>
> Assisted-by: LLM
> Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261105121733.643754-1-andrey.drobyshev@virtuozzo.com?part=1
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next prev parent reply other threads:[~2026-11-05 12:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 12:17 [Devel] [PATCH hci-8.1 v2 0/2] vfio, KVM: kvm reference leak and debugfs clash on live update Andrey Drobyshev
2026-11-05 12:17 ` [Devel] [PATCH hci-8.1 1/2] vfio: take the kvm reference only for drivers that read device->kvm Andrey Drobyshev
2026-11-05 12:23 ` no-reply [this message]
2026-11-05 12:54 ` Konstantin Khorenko
2026-11-05 12:17 ` [Devel] [PATCH hci-8.1 2/2] KVM: remove the VM's debugfs directory when its fd is released Andrey Drobyshev
2026-11-05 12:24 ` no-reply
2026-11-05 12:54 ` Konstantin Khorenko
2026-11-05 12:54 ` [Devel] [PATCH hci-8.1 v2 0/2] vfio, KVM: kvm reference leak and debugfs clash on live update Konstantin Khorenko
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