linux-kernel - Re: [PATCH v7 03/17] iommu: generalize the batched sync after map interface

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Message-ID: <20250317134439.GX1322339@unreal>
Date: Mon, 17 Mar 2025 15:44:39 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...pe.ca>,
	Robin Murphy <robin.murphy@....com>, Jens Axboe <axboe@...nel.dk>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Sagi Grimberg <sagi@...mberg.me>, Keith Busch <kbusch@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>,
	Yishai Hadas <yishaih@...dia.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Jérôme Glisse <jglisse@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
	linux-rdma@...r.kernel.org, iommu@...ts.linux.dev,
	linux-nvme@...ts.infradead.org, linux-pci@...r.kernel.org,
	kvm@...r.kernel.org, linux-mm@...ck.org,
	Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v7 03/17] iommu: generalize the batched sync after map
 interface

On Mon, Mar 17, 2025 at 10:52:11AM +0100, Niklas Schnelle wrote:
> On Wed, 2025-02-05 at 16:40 +0200, Leon Romanovsky wrote:
> > From: Christoph Hellwig <hch@....de>
> > 
> > For the upcoming IOVA-based DMA API we want to use the interface batch the
> > sync after mapping multiple entries from dma-iommu without having a
> > scatterlist.
> > 
> > For that move more sanity checks from the callers into __iommu_map and
> > make that function available outside of iommu.c as iommu_map_nosync.
> > 
> > Add a wrapper for the map_sync as iommu_sync_map so that callers don't
> > need to poke into the methods directly.
> > 
> > Signed-off-by: Christoph Hellwig <hch@....de>
> > Acked-by: Will Deacon <will@...nel.org>
> > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > ---
> >  drivers/iommu/iommu.c | 65 +++++++++++++++++++------------------------
> >  include/linux/iommu.h |  4 +++
> >  2 files changed, 33 insertions(+), 36 deletions(-)
> > 
> > 
> --- snip ---
> > +
> >  	return mapped;
> >  
> >  out_err:
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index 38c65e92ecd0..7ae9aa3a1894 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -857,6 +857,10 @@ extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
> >  extern struct iommu_domain *iommu_get_dma_domain(struct device *dev);
> >  extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
> >  		     phys_addr_t paddr, size_t size, int prot, gfp_t gfp);
> > +int iommu_map_nosync(struct iommu_domain *domain, unsigned long iova,
> > +		phys_addr_t paddr, size_t size, int prot, gfp_t gfp);
> > +int iommu_sync_map(struct iommu_domain *domain, unsigned long iova,
> > +		size_t size);
> 
> There are two different word orders in the function names.
> iommu_sync_map() vs iommu_map_nosync(). I'd prefer to be consistent
> with e.g. iommu_map_sync() vs iommu_map_nosync().

The naming came from refactoring different functions, one was simple *_map() and
another was iotlb_*_sync(), but yes we can name it consistently.

Thanks

> 
> >  extern size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova,
> >  			  size_t size);
> >  extern size_t iommu_unmap_fast(struct iommu_domain *domain,
>