Message-ID: <4ad0d2b9-2465-b42d-c0f9-b48caadfd72c@linux.ibm.com>
Date:   Wed, 15 Feb 2023 13:00:08 -0500
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Subject: Re: [PATCH v6 4/6] s390/pci: Use dma-iommu layer
To:     Niklas Schnelle <schnelle@linux.ibm.com>,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Wenjia Zhang <wenjia@linux.ibm.com>
Cc:     Gerd Bayer <gbayer@linux.ibm.com>,
        Pierre Morel <pmorel@linux.ibm.com>, iommu@lists.linux.dev,
        linux-s390@vger.kernel.org, borntraeger@linux.ibm.com,
        hca@linux.ibm.com, gor@linux.ibm.com,
        gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com,
        svens@linux.ibm.com, linux-kernel@vger.kernel.org,
        Julian Ruess <julianr@linux.ibm.com>
References: <20230215120327.947336-1-schnelle@linux.ibm.com>
 <20230215120327.947336-5-schnelle@linux.ibm.com>
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From:   Matthew Rosato <mjrosato@linux.ibm.com>
In-Reply-To: <20230215120327.947336-5-schnelle@linux.ibm.com>
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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@linux.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