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Date:   Mon, 15 Aug 2022 14:04:37 -0700
From:   Andres Freund <andres@anarazel.de>
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Jens Axboe <axboe@kernel.dk>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Guenter Roeck <linux@roeck-us.net>,
        linux-kernel@vger.kernel.org, Greg KH <gregkh@linuxfoundation.org>,
        c@redhat.com
Subject: Re: upstream kernel crashes
Message-ID: <20220815210437.saptyw6clr7datun@awork3.anarazel.de>
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On 2022-08-15 13:53:31 -0700, Andres Freund wrote:
> The reason the debug patch didn't change anything, and that my debug printk
> didn't show, is that gcp uses the legacy paths...
> 
> If there were a bug in the legacy path, it'd explain why the problem only
> shows on gcp, and not in other situations.
> 
> I'll queue testing the legacy path with the equivalent change.

Booting with the equivalent change, atop 5.19, in the legacy setup_vq()
reliably causes boot to hang:

[    0.718768] ACPI: button: Sleep Button [SLPF]
[    0.721989] ACPI: \_SB_.LNKC: Enabled at IRQ 11
[    0.722688] adebug: use legacy: 0
[    0.722724] virtio-pci 0000:00:03.0: virtio_pci: leaving for legacy driver
[    0.724286] adebug: probe modern: -19
[    0.727353] ACPI: \_SB_.LNKD: Enabled at IRQ 10
[    0.728719] adebug: use legacy: 0
[    0.728766] virtio-pci 0000:00:04.0: virtio_pci: leaving for legacy driver
[    0.730422] adebug: probe modern: -19
[    0.733552] ACPI: \_SB_.LNKA: Enabled at IRQ 10
[    0.734923] adebug: use legacy: 0
[    0.734957] virtio-pci 0000:00:05.0: virtio_pci: leaving for legacy driver
[    0.736426] adebug: probe modern: -19
[    0.739039] ACPI: \_SB_.LNKB: Enabled at IRQ 11
[    0.740350] adebug: use legacy: 0
[    0.740390] virtio-pci 0000:00:06.0: virtio_pci: leaving for legacy driver
[    0.742142] adebug: probe modern: -19
[    0.747627] adebug: legacy setup_vq
[    0.748243] virtio-pci 0000:00:05.0: adebug: legacy: not limiting queue size, only 256
[    0.751081] adebug: legacy setup_vq
[    0.751110] virtio-pci 0000:00:05.0: adebug: legacy: not limiting queue size, only 256
[    0.754028] adebug: legacy setup_vq
[    0.754059] virtio-pci 0000:00:05.0: adebug: legacy: not limiting queue size, only 1
[    0.757760] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[    0.759135] 00:03: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    0.760399] 00:04: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
[    0.761610] 00:05: ttyS2 at I/O 0x3e8 (irq = 6, base_baud = 115200) is a 16550A
[    0.762923] 00:06: ttyS3 at I/O 0x2e8 (irq = 7, base_baud = 115200) is a 16550A
[    0.764222] Non-volatile memory driver v1.3
[    0.768857] adebug: legacy setup_vq
[    0.768882] virtio-pci 0000:00:06.0: adebug: legacy: not limiting queue size, only 256
[    0.773002] Linux agpgart interface v0.103
[    0.775424] loop: module loaded
[    0.780513] adebug: legacy setup_vq
[    0.780538] virtio-pci 0000:00:03.0: adebug: legacy: limiting queue size from 8192 to 1024
[    0.784075] adebug: legacy setup_vq
[    0.784104] virtio-pci 0000:00:03.0: adebug: legacy: limiting queue size from 8192 to 1024
[    0.787073] adebug: legacy setup_vq
[    0.787101] virtio-pci 0000:00:03.0: adebug: legacy: limiting queue size from 8192 to 1024
[    0.790379] scsi host0: Virtio SCSI HBA
[    0.795968] Freeing initrd memory: 7236K

Greetings,

Andres Freund