Date:   Mon, 29 Nov 2021 15:42:56 +0000
From:   Jean-Philippe Brucker <jean-philippe@linaro.org>
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Eric Auger <eric.auger@redhat.com>, joro@8bytes.org,
        will@kernel.org, jasowang@redhat.com,
        virtualization@lists.linux-foundation.org,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        sebastien.boeuf@intel.com, kevin.tian@intel.com,
        pasic@linux.ibm.com
Subject: Re: [PATCH v2 4/5] iommu/virtio: Pass end address to
 viommu_add_mapping()
Message-ID: <YaT1ACdwq1n4YBug@myrica>
References: <20211123155301.1047943-1-jean-philippe@linaro.org>
 <20211123155301.1047943-5-jean-philippe@linaro.org>
 <7b79fe9b-9d51-8bda-2868-b48781f07fc9@redhat.com>
 <20211127180742-mutt-send-email-mst@kernel.org>
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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