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Date: Wed, 22 May 2024 20:20:25 -0300
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Gerd Bayer <gbayer@linux.ibm.com>,
	Matthew Rosato <mjrosato@linux.ibm.com>, linux-s390@vger.kernel.org,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH 3/3] vfio/pci: Enable VFIO_PCI_MMAP for s390
Message-ID: <20240522232025.GH69273@ziepe.ca>
References: <20240521-vfio_pci_mmap-v1-0-2f6315e0054e@linux.ibm.com>
 <20240521-vfio_pci_mmap-v1-3-2f6315e0054e@linux.ibm.com>
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In-Reply-To: <20240521-vfio_pci_mmap-v1-3-2f6315e0054e@linux.ibm.com>

On Tue, May 21, 2024 at 02:14:59PM +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 VFIO_PCI_MMAP can be enabled
> on all s390 systems with native PCI allowing vfio-pci user-space
> applications direct access to mapped resources.
> 
> Link: https://lore.kernel.org/all/c5ba134a1d4f4465b5956027e6a4ea6f6beff969.camel@linux.ibm.com/
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
>  drivers/vfio/pci/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index 15821a2d77d2..814aa0941d61 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -8,7 +8,7 @@ config VFIO_PCI_CORE
>  	select IRQ_BYPASS_MANAGER
>  
>  config VFIO_PCI_MMAP
> -	def_bool y if !S390
> +	def_bool y
>  	depends on VFIO_PCI_CORE

Should we just purge this kconfig entirely? It is never meaningfully n now?

Jason