linux-kernel - Re: [PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is disconnected

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Message-ID: <20181108214900.GB2932@localhost.localdomain>
Date:   Thu, 8 Nov 2018 14:49:00 -0700
From:   Keith Busch <keith.busch@...el.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Alexandru Gagniuc <mr.nuke.me@...il.com>,
        linux-pci@...r.kernel.org, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, shyam_iyer@...l.com,
        linux-kernel@...r.kernel.org,
        Jonathan Derrick <jonathan.derrick@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lukas Wunner <lukas@...ner.de>,
        Russell Currey <ruscur@...sell.cc>,
        Sam Bobroff <sbobroff@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is
 disconnected

On Thu, Nov 08, 2018 at 02:09:17PM -0600, Bjorn Helgaas wrote:
> 
> I'm having second thoughts about this.  One thing I'm uncomfortable
> with is that sprinkling pci_dev_is_disconnected() around feels ad hoc
> instead of systematic, in the sense that I don't know how we convince
> ourselves that this (and only this) is the correct place to put it.

You know how the kernel provides ZERO_PAGE, wouldn't it be cool if we
also had a ONES_PAGE and could remap all virtual addresses from a memory
mapped device to that page on an ungraceful disconnect? I do not know
how to accomplish that, so might just be crazy talk... But if it is
possible, that would be a pretty nifty way to solve this problem.