linux-kernel - Re: [PATCH v2 4/5] iommu/virtio: Pass end address to viommu_add

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Date:   Mon, 29 Nov 2021 15:42:56 +0000
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Eric Auger <eric.auger@...hat.com>, joro@...tes.org,
        will@...nel.org, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        sebastien.boeuf@...el.com, kevin.tian@...el.com,
        pasic@...ux.ibm.com
Subject: Re: [PATCH v2 4/5] iommu/virtio: Pass end address to
 viommu_add_mapping()

On Sat, Nov 27, 2021 at 06:09:56PM -0500, Michael S. Tsirkin wrote:
> > > -static int viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
> > > -			      phys_addr_t paddr, size_t size, u32 flags)
> > > +static int viommu_add_mapping(struct viommu_domain *vdomain, u64 iova, u64 end,
> > > +			      phys_addr_t paddr, u32 flags)
> > >  {
> > >  	unsigned long irqflags;
> > >  	struct viommu_mapping *mapping;
> 
> I am worried that API changes like that will cause subtle
> bugs since types of arguments change but not their
> number. If we forgot to update some callers it will all be messed up.
> 
> How about passing struct Range instead?

I gave struct range a try but it looks messier overall since it would only
be used to pass arguments. I think the update is safe enough because there
is one caller for viommu_add_mapping() and two for viommu_del_mappings(),
at the moment.

Thanks,
Jean