linux-kernel - Re: [PATCH 2/4] virtio-mem: Fix probe failed when modprobe virtio

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Date:   Mon, 28 Nov 2022 09:22:40 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Li Zetao <lizetao1@...wei.com>, mst@...hat.com,
        jasowang@...hat.com, pbonzini@...hat.com, stefanha@...hat.com,
        axboe@...nel.dk, kraxel@...hat.com, ericvh@...il.com,
        lucho@...kov.net, asmadeus@...ewreck.org, linux_oss@...debyte.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, rusty@...tcorp.com.au
Cc:     virtualization@...ts.linux-foundation.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: Re: [PATCH 2/4] virtio-mem: Fix probe failed when modprobe virtio_mem

On 28.11.22 03:10, Li Zetao wrote:
> When doing the following test steps, an error was found:
>    step 1: modprobe virtio_mem succeeded
>      # modprobe virtio_mem      <-- OK
> 
>    step 2: fault injection in virtio_mem_init()
>      # modprobe -r virtio_mem   <-- OK
>      # ...
>        CPU: 0 PID: 1837 Comm: modprobe Not tainted
>        6.1.0-rc6-00285-g6a1e40c4b995-dirty
>        Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>        Call Trace:
>         <TASK>
>         should_fail.cold+0x5/0x1f
>         ...
>         virtio_mem_init_hotplug+0x9ae/0xe57 [virtio_mem]
>         virtio_mem_init.cold+0x327/0x339 [virtio_mem]
>         virtio_mem_probe+0x48e/0x910 [virtio_mem]
>         virtio_dev_probe+0x608/0xae0
>         ...
>         </TASK>
>        virtio_mem virtio4: could not reserve device region
>        virtio_mem: probe of virtio4 failed with error -16
> 
>    step 3: modprobe virtio_net failed

virtio_net ?

>      # modprobe virtio_mem       <-- failed
>        virtio_mem: probe of virtio4 failed with error -16
> 
> The root cause of the problem is that the virtqueues are not
> stopped on the error handling path when virtio_mem_init()
> fails in virtio_mem_probe(), resulting in an error "-ENOENT"
> returned in the next modprobe call in setup_vq().
> 
> virtio_pci_modern_device uses virtqueues to send or
> receive message, and "queue_enable" records whether the
> queues are available. In vp_modern_find_vqs(), all queues
> will be selected and activated, but once queues are enabled
> there is no way to go back except reset.
> 
> Fix it by reset virtio device on error handling path. After
> virtio_mem_init_vq() succeeded, all virtqueues should be
> stopped on error handling path.
> 
> Fixes: 1fcf0512c9c8 ("virtio_pci: modern driver")

That commit is from 2014. virtio-mem was merged in 2020

Fixes: 5f1f79bbc9e2 ("virtio-mem: Paravirtualized memory hotplug")

> Signed-off-by: Li Zetao <lizetao1@...wei.com>
> ---
>   drivers/virtio/virtio_mem.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
> index 0c2892ec6817..c7f09c2ce982 100644
> --- a/drivers/virtio/virtio_mem.c
> +++ b/drivers/virtio/virtio_mem.c
> @@ -2793,6 +2793,7 @@ static int virtio_mem_probe(struct virtio_device *vdev)
>   
>   	return 0;
>   out_del_vq:
> +	virtio_reset_device(vdev);
>   	vdev->config->del_vqs(vdev);
>   out_free_vm:
>   	kfree(vm);


Apart from that

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb