linux-kernel - Re: [Xen-devel] [PATCH 2/5] xen/pciback: Support pci_reset

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Message-ID: <4F072717.8090006@redhat.com>
Date:	Fri, 06 Jan 2012 11:53:43 -0500
From:	Don Dutile <ddutile@...hat.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Ian Campbell <Ian.Campbell@...rix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [Xen-devel] [PATCH 2/5] xen/pciback: Support pci_reset_function,
 aka FLR or D3 support.

On 01/05/2012 04:34 PM, Konrad Rzeszutek Wilk wrote:
> On Thu, Jan 05, 2012 at 01:58:50PM -0500, Don Dutile wrote:
>> On 01/05/2012 05:24 AM, Ian Campbell wrote:
>>> On Thu, 2012-01-05 at 00:46 +0000, Konrad Rzeszutek Wilk wrote:
>>>> We use the __pci_reset_function_locked to perform the action.
>>>> Also on attaching ("bind") and detaching ("unbind") we save and
>>>> restore the configuration states. When the device is disconnected
>>> >from a guest we use the "pci_reset_function" to also reset the
>>>> device before being passed to another guest.
>>>
>>> Currently I thought the toolstack was supposed to do the reset (by
>>> writing to the reset node in sysfs) as it was (de)assigning devices
>>> to/from guests. That's not to say that there isn't an argument for
>>> preferring to do it kernels side but it would be interesting to make
>>> that argument explicitly.
>>>
>>> I guess the toolstack doesn't currently save/restore the configuration
>>> state, could it though? I guess the state is all available in sysfs. On
>> pci_reset_function() saves the config state before doing a fcn-level reset.
>>
>> the libvirt toolstack handles the unbind/reset/bind functionality
>> and is used by kvm for it's device assignment.
>
> The KVM assigned PCI module does the call as well via the ioctls when
> assigning/de-assigning the PCI device. Look in 'kvm_free_assigned_device'
> and in 'kvm_vm_ioctl_assign_device'.
>
> Is that what you mean by the unbind/reset/bind functionality - the ioctl
> call?
>
It's done in both places (libvirt & kvm-ioctl).

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