linux-kernel - Re: [PATCH][RFC] PCI: Add "pci=blacklist_dev=" parameter to blacklist specific devices

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Date:   Fri, 24 Jan 2020 11:27:43 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-pci@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH][RFC] PCI: Add "pci=blacklist_dev=" parameter to
 blacklist specific devices

On Fri, Jan 24, 2020 at 10:42:48PM +0800, Chen Yu wrote:
> It was found that on some platforms the bogus pci device might bring
> troubles to the system. For example, on a MacBookPro the system could
> not be power off or suspended due to internal pci resource confliction
> between bogus pci device and [io 0x1804]. Another case is that, once
> resumed from hibernation on a VM, the pci config space of a pci device
> is corrupt.
> 
> To narrow down and benefit future debugging for such kind of issues,
> introduce the command line blacklist_dev=<vendor:device_id>> to blacklist
> such pci devices thus they will not be scanned thus not visible after
> bootup. For example,
> 
>  pci.blacklist_dev=8086:293e
> 
> forbid the audio device to be exposed to the OS.

This feels really unsafe to me.  Just because Linux ignores the device
doesn't mean the device will ignore I/O requests.  I think we should
call this pci.disable_dev and clear the device's I/O Space Enable,
Memory Space Enable and Bus Master Enable bits (in the Command register,
config space offset 4).