linux-kernel - Re: [PATCH v4 4/4] vfio/pci: Enable PCI resource mmap() on s390 and remove VFIO_PCI

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Message-ID: <20240704101634.30b542a2.alex.williamson@redhat.com>
Date: Thu, 4 Jul 2024 10:16:34 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: 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>, Gerd
 Bayer <gbayer@...ux.ibm.com>, Matthew Rosato <mjrosato@...ux.ibm.com>,
 Jason Gunthorpe <jgg@...pe.ca>, linux-s390@...r.kernel.org,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v4 4/4] vfio/pci: Enable PCI resource mmap() on s390 and
 remove VFIO_PCI_MMAP

On Wed, 26 Jun 2024 13:15:51 +0200
Niklas Schnelle <schnelle@...ux.ibm.com> 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>
> Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> Reviewed-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(-)

I think you're planning a v5 which drops patch 3/ of this series and
finesses the commit log of patch 2/ a bit.  This has become much less a
vfio series, so if you want to commit through s390,

Acked-by: Alex Williamson <alex.williamson@...hat.com>

Thanks,
Alex

> 
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index bf50ffa10bde..c3bcb6911c53 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -7,10 +7,6 @@ config VFIO_PCI_CORE
>  	select VFIO_VIRQFD
>  	select IRQ_BYPASS_MANAGER
>  
> -config VFIO_PCI_MMAP
> -	def_bool y if !S390
> -	depends on VFIO_PCI_CORE
> -
>  config VFIO_PCI_INTX
>  	def_bool y if !S390
>  	depends on VFIO_PCI_CORE
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 0e9d46575776..c08d0f7bb500 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -120,9 +120,6 @@ static void vfio_pci_probe_mmaps(struct vfio_pci_core_device *vdev)
>  
>  		res = &vdev->pdev->resource[bar];
>  
> -		if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP))
> -			goto no_mmap;
> -
>  		if (!(res->flags & IORESOURCE_MEM))
>  			goto no_mmap;
>  
>