linux-kernel - Re: [PATCH 0/3] PCI: Rework config space locking, add INTx masking services

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Message-ID: <4E984BD2.6090907@siemens.com>
Date:	Fri, 14 Oct 2011 16:48:50 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Brian King <brking@...ux.vnet.ibm.com>
Subject: Re: [PATCH 0/3] PCI: Rework config space locking, add INTx masking
 services

On 2011-10-06 17:48, Jesse Barnes wrote:
> On Mon, 12 Sep 2011 18:54:01 +0200
> Jan Kiszka <jan.kiszka@...mens.com> wrote:
> 
>> This series tries to heal the currently broken locking scheme around PCI
>> config space accesses.
>>
>> We have an interface lock out access via sysfs, but that service wrongly
>> assumes it is only called by one instance at a time for some device. So
>> two loops doing
>>
>> echo 1 > /sys/bus/pci/devices/<some-device>/reset
>>
>> in parallel will trigger a kernel BUG at the moment.
>>
>> Besides synchronizing with user space, we also need to manage config
>> space access of generic PCI drivers. They need to mask legacy interrupt
>> lines while the specific driver runs in user space or a guest OS.
>>
>> The approach taken here is provide mutex-like locking for general
>> access - which still requires a special mechanism due to requirements of
>> the IBM Power RAID SCSI driver. Furthermore, INTx masking is now
>> available via the PCI core and synchronized via the internal pci_lock.
>>
>> Not sure who may want to take this, so I'm CC'ing broadly.
> 
> ISTR a bunch of discussion about this (just back from lots of work
> travel and vacation, sorry I missed most of it).
> 
> Is this the agreed upon way of handling it?  If so, can I get some
> Reviewed/Acked-bys from people?

I hope this is acceptable. These changes are required for further
improvements of the KVM device assignment support (INTx sharing). So I
would appreciate any ack or whatever feedback as well.

Thanks,
Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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