linux-kernel - Re: [PATCH v6 4/6] s390/pci: Use dma-iommu layer

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Message-ID: <59a61553a81282fed88c03af096b2a0830b94302.camel@linux.ibm.com>
Date:   Fri, 17 Feb 2023 09:51:50 +0100
From:   Niklas Schnelle <schnelle@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Wenjia Zhang <wenjia@...ux.ibm.com>
Cc:     Gerd Bayer <gbayer@...ux.ibm.com>,
        Pierre Morel <pmorel@...ux.ibm.com>, iommu@...ts.linux.dev,
        linux-s390@...r.kernel.org, borntraeger@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, linux-kernel@...r.kernel.org,
        Julian Ruess <julianr@...ux.ibm.com>
Subject: Re: [PATCH v6 4/6] s390/pci: Use dma-iommu layer

On Wed, 2023-02-15 at 13:00 -0500, Matthew Rosato wrote:
> On 2/15/23 7:03 AM, Niklas Schnelle wrote:
> > While s390 already has a standard IOMMU driver and previous changes have
> > added I/O TLB flushing operations this driver is currently only used for
> > user-space PCI access such as vfio-pci. For the DMA API s390 instead
> > utilizes its own implementation in arch/s390/pci/pci_dma.c which drives
> > the same hardware and shares some code but requires a complex and
> > fragile hand over between DMA API and IOMMU API use of a device and
> > despite code sharing still leads to significant duplication and
> > maintenance effort. Let's utilize the common code DMAP API
> > implementation from drivers/iommu/dma-iommu.c instead allowing us to
> > get rid of arch/s390/pci/pci_dma.c.
> > 
> > Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> > ---
> 
> FYI, this patch doesn't fit on top of iommu-next, I'd guess at least due to baolu's 'Retire detach_dev callback' series, which removed .detach_dev and added .set_platform_dma_ops for s390-iommu.  That's relevant here, because now that this patch enables dma-iommu for s390 and removes the platform DMA ops it must now remove .set_platform_dma_ops/s390_iommu_set_platform_dma for s390-iommu.
> 
> Matt


Ok, yes this series is currently against v6.2-rc8. Should I rebase
against iommu-next and send a v7 before further review or after?

Thanks,
Niklas