linux-kernel - Re: [RFC] pci: Rework config space blocking services

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Date:	Tue, 06 Sep 2011 10:48:04 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Brian King <brking@...ibm.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [RFC] pci: Rework config space blocking services

On 2011-09-06 10:47, Michael S. Tsirkin wrote:
> On Tue, Sep 06, 2011 at 10:27:45AM +0200, Jan Kiszka wrote:
>> On 2011-09-06 10:04, Michael S. Tsirkin wrote:
>>> On Tue, Sep 06, 2011 at 09:18:13AM +0200, Jan Kiszka wrote:
>>>>>> @@ -401,36 +403,58 @@ int pci_vpd_truncate(struct pci_dev *dev, size_t size)
>>>>>>  EXPORT_SYMBOL(pci_vpd_truncate);
>>>>>>
>>>>>>  /**
>>>>>> - * pci_block_user_cfg_access - Block userspace PCI config reads/writes
>>>>>> + * pci_block_cfg_access - Block PCI config reads/writes
>>>>>
>>>>> This comment seems confusing. We don't in fact block all config
>>>>> reads writes. Instead we block userspace accesses and
>>>>> concurrent block requests.
>>>>
>>>> I'm open for a better suggestion that summarize the more verbose (and
>>>> hopefully clearer) explanation below.
>>>
>>> I think the problem is, it doesn't block config access
>>> and we call it pci_block_cfg_access.
>>>
>>> Thinking about it, doesn't this behave somewhat like a lock?
>>> How about
>>>
>>> pci_user_cfg_access_trylock
>>> pci_user_cfg_access_lock
>>> pci_user_cfg_access_unlock
>>>
>>> And then:
>>>  * pci_user_cfg_access_lock - Lock userspace PCI config access
>>
>> Except that the "userspace" here is still only half of the truth
> 
> It's the name of the lock :)

Ah, blind. That has to be change as well of course (pci_cfg_access_*lock).

Jan

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