linux-kernel - Re: [PATCH v4] sparc/PCI: Fix for panic while enabling SR-IOV

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Date:	Wed, 30 Mar 2016 10:31:18 -0500
From:	Babu Moger <babu.moger@...cle.com>
To:	David Miller <davem@...emloft.net>
Cc:	bhelgaas@...gle.com, wangyijing@...wei.com,
	sowmini.varadhan@...cle.com, jiang.liu@...ux.intel.com,
	eric.snowberg@...cle.com, yinghai@...nel.org,
	dan.j.williams@...el.com, sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	ethan.zhao@...cle.com
Subject: Re: [PATCH v4] sparc/PCI: Fix for panic while enabling SR-IOV

Hi David,

On 3/29/2016 7:57 PM, David Miller wrote:
> From: Babu Moger <babu.moger@...cle.com>
> Date: Thu, 24 Mar 2016 13:02:22 -0700
> 
>> We noticed this panic while enabling SR-IOV in sparc.
>  ...
>> SR-IOV code looks for arch specific data while enabling
>> VFs. When VF device is added, driver probe function makes set
>> of calls to initialize the pci device. Because the VF device is
>> added different way than the normal PF device(which happens via
>> of_create_pci_dev for sparc), some of the arch specific initialization
>> does not happen for VF device.  That causes panic when archdata is
>> accessed.
>>
>> To fix this, I have used already defined weak function
>> pcibios_setup_device to copy archdata from PF to VF.
>> Also verified the fix.
>>
>> Signed-off-by: Babu Moger <babu.moger@...cle.com>
>> Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
>> Reviewed-by: Ethan Zhao <ethan.zhao@...cle.com>
> 
> Looks good, applied and queued up for -stable, thanks.

Thanks.

> 
> Just a note, I am assuming that the VFs are not instantiated in the
> device tree.  Because when you just memcpy the arch data over from the
> PF, one thing we end up doing is using the device node of the PF.

No. VFs are not instantiated in device tree(/proc/device-tree)

> 
> I slightly cringed at the memcpy, because at least one of these
> pointers are to objects which are reference counted, the OF device.
> 
> Generally speaking we don't really support hot-plug for OF probed
> devices, but if we did all of the device tree pointers have to be
> refcounted properly.
> 
> So in the long term that whole sequence where we go:
> 
> 	struct dev_archdata *sd;
>  ...
> 	sd = &dev->dev.archdata;
> 	sd->iommu = pbm->iommu;
> 	sd->stc = &pbm->stc;
> 	sd->host_controller = pbm;
> 	sd->op = op = of_find_device_by_node(node);
> 	sd->numa_node = pbm->numa_node;
> 
> should be encapsulated into a helper function, and both
> of_create_pci_dev() and this new pcibios_setup_device() can
> invoke it.
> 

Yes. Agree. We need to refactor the whole of_create_pci_dev path to support
hot-plug for the long term. I will start looking at it. For now we should be
fine with the current patch. thanks