netdev - Re: [PATCH V8 9/9] virtio: Intel IFC VF driver for VDPA

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Date:   Thu, 26 Mar 2020 21:56:48 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jason Gunthorpe <jgg@...lanox.com>
Cc:     mst@...hat.com, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        maxime.coquelin@...hat.com, cunming.liang@...el.com,
        zhihong.wang@...el.com, rob.miller@...adcom.com,
        xiao.w.wang@...el.com, lingshan.zhu@...el.com, eperezma@...hat.com,
        lulu@...hat.com, parav@...lanox.com, kevin.tian@...el.com,
        stefanha@...hat.com, rdunlap@...radead.org, hch@...radead.org,
        aadam@...hat.com, jiri@...lanox.com, shahafs@...lanox.com,
        hanand@...inx.com, mhabets@...arflare.com, gdawar@...inx.com,
        saugatm@...inx.com, vmireyno@...vell.com,
        Bie Tiwei <tiwei.bie@...el.com>
Subject: Re: [PATCH V8 9/9] virtio: Intel IFC VF driver for VDPA


On 2020/3/26 下午8:17, Jason Gunthorpe wrote:
> On Thu, Mar 26, 2020 at 01:50:53PM +0800, Jason Wang wrote:
>
>>>> +	adapter->vdpa.dma_dev = dev;
>>>> +	ret = vdpa_register_device(&adapter->vdpa);
>>>> +	if (ret) {
>>>> +		IFCVF_ERR(adapter->dev, "Failed to register ifcvf to vdpa bus");
>>>> +		goto err_msix;
>>>> +	}
>>>> +
>>>> +	return 0;
>>>> +
>>>> +err_msix:
>>>> +	put_device(&adapter->vdpa.dev);
>>>> +	return ret;
>>>> +err_alloc:
>>>> +	pci_free_irq_vectors(pdev);
>>>> +err_vectors:
>>>> +	pci_release_regions(pdev);
>>>> +err_regions:
>>>> +	pci_disable_device(pdev);
>>>> +err_enable:
>>>> +	return ret;
>>>> +}
>>> I personally don't like seeing goto unwinds with multiple returns, and
>>> here I think it is actually a tiny bug.
>>>
>>> All touches to the PCI device must stop before the driver core
>>> remove() returns - so these pci function cannot be in the kref put
>>> release function anyhow.
>>
>> I'm not sure I get here. IFCVF held refcnt of its PCI parent, so it looks to
>> me it's safe to free PCI resources in vDPA free callback?
> The refcnt doesn't prevent the driver core from re-binding the
> pci_device to another driver. Then the refcount put would do a
> pci_disable_device() after another driver has started
>
> For this reason all touches to a struct pci_device must stop before
> remove returns.
>
> Jason


Ok, will send a new version shortly.

Thanks


>