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

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Date: Thu, 27 Jun 2024 13:12:30 +0200
From: Alexandra Winter <wintera@...ux.ibm.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>,
        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 26.06.24 13:20, Niklas Schnelle wrote:
> 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
> 

For a v5:
I am not an expert in English grammar, but I think some commas (',')
may help with reading your very good commit messages.

Acked-by: Alexandra Winter <wintera@...ux.ibm.com>