linux-kernel - Re: VFs go missing with latest kernel

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Date:	Tue, 31 Jan 2012 16:05:00 -0700
From:	David Ahern <daahern@...co.com>
To:	"Rose, Gregory V" <gregory.v.rose@...el.com>
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: VFs go missing with latest kernel

On 01/31/2012 03:58 PM, Rose, Gregory V wrote:
>> Note that all of the even numbered VFs have disappeared. Accordingly,
>> trying to launch the VM to which the VFs are assigned fails. git bisect
>> pointed to this commit:
>>
>> 0224d663063d542b3d829706f3fcbd0f640f19b3 is the first bad commit
>> commit 0224d663063d542b3d829706f3fcbd0f640f19b3
>> Author: Greg Rose <gregory.v.rose@...el.com>
>> Date:   Fri Oct 14 02:57:14 2011 +0000
>>
>>     igb: Check if subordinate VFs are assigned to virtual machines
>>
>>     Kvm and the Xen pci-back driver will set a flag in the virtual
>> function
>>     pci device dev_flags when the VF is assigned to a guest VM.  Before
>>     destroying subordinate VFs check to see if the flag is set and if so
>>     skip the call to pci_disable_sriov() to avoid system crashes.
>>
>>     Copy the maintainer for the Xen pci-back driver.  Also CC'ing
>>     maintainers of all drivers found to call pci_disable_sriov().
>>
>>
>> Sure enough reverting the patch on 3.3.0-rc1 makes the VFs visible again.
>>
>> I am hitting some other problem trying to use the VF on 3.3.0-rc1 -- KVM
>> fails the KVM_CAP_IOMMU check though the server has one (works fine with
>> the older kernel) and it is built into the kernel. Debugging that
>> problem now.
> 
> I'll see if I can reproduce that.  Is this all after a fresh boot with no unloading/reloading of the PF driver?

Build kernel, reboot, run lspci - note missing VFs.

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