linux-kernel - Re: [PATCH v2 3/3] vfio/pci: Enable PCI resource mmap() on s390 and remove VFIO_PCI

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Message-ID: <20240523151931.GK69273@ziepe.ca>
Date: Thu, 23 May 2024 12:19:31 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: 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>, linux-s390@...r.kernel.org,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v2 3/3] vfio/pci: Enable PCI resource mmap() on s390 and
 remove VFIO_PCI_MMAP

On Thu, May 23, 2024 at 01:10:16PM +0200, Niklas Schnelle wrote:
> With the introduction of memory I/O (MIO) instructions enbaled in commit
> 71ba41c9b1d9 ("s390/pci: provide support for MIO instructions") s390
> gained support for direct user-space access to mapped PCI resources.
> Even without those however user-space can access mapped PCI resources
> via the s390 specific MMIO syscalls. Thus mmap() can and should be
> supported on all s390 systems with native PCI. Since VFIO_PCI_MMAP
> enablement for s390 would make it unconditionally true and thus
> pointless just remove it entirely.
> 
> Link: https://lore.kernel.org/all/c5ba134a1d4f4465b5956027e6a4ea6f6beff969.camel@linux.ibm.com/
> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> ---
>  drivers/vfio/pci/Kconfig         | 4 ----
>  drivers/vfio/pci/vfio_pci_core.c | 3 ---
>  2 files changed, 7 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason