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

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Date:	Thu, 6 Oct 2011 08:48:53 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Jan Kiszka <jan.kiszka@...mens.com>
Cc:	linux-pci@...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,
	Brian King <brking@...ux.vnet.ibm.com>
Subject: Re: [PATCH 0/3] PCI: Rework config space locking, add INTx masking
 services

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?

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center

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