linux-kernel - Re: [PATCH v4 2/4] s390/pci: Add quirk support and set pdev-non_compliant

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Message-ID: <b22a641f84b3e3259777ff54576f3a2f1435785b.camel@linux.ibm.com>
Date: Wed, 26 Jun 2024 13:20:45 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Bjorn Helgaas <helgaas@...nel.org>, Christoph Hellwig <hch@....de>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens
 <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>,
        Christian Borntraeger
 <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Alex
 Williamson <alex.williamson@...hat.com>,
        Gerd Bayer <gbayer@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc: linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v4 2/4] s390/pci: Add quirk support and set
 pdev-non_compliant_bars for ISM devices

On Wed, 2024-06-26 at 13:15 +0200, Niklas Schnelle wrote:
> On s390 there is a virtual PCI device called ISM which has a few
> pecularities. For one it claims to have a 256 TiB PCI BAR which leads to
> any attempt to ioremap() in its entirety failing. This is problematic
> since mapping the whole BAR is the default behavior of for example QEMU
> with VFIO_PCI_MMAP enabled.
> 
> Even if one tried to map this BAR only partially the mapping would not
> be usable on systems with MIO support enabled unless using the function
> handle based PCI instructions directly. This is because of another
> oddity in that this virtual PCI device does not support the newer memory
> I/O (MIO) PCI instructions and legacy PCI instructions are not
> accessible through writeq()/readq() or by user-space when MIO is in use.
> 
> Indicate that ISM's BAR is special and does not conform to PCI BAR
> expectations by setting pdev->non_compliant_bars such that drivers not
> specifically developed for ISM can easily ignore it. To this end add
> basic PCI quirks support modeled after x86's arch/x86/pci/fixup.c and
> move the ISM device's PCI ID to the common header to make it accessible.
> Also enable CONFIG_PCI_QUIRKS whenever CONFIG_PCI is enabled.
> 
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> ---
> 


Fixed the '-' instead of '->' typo in the patch subject locally.
Chances are we get a v5 anyway.

Thanks,
Niklas