linux-kernel - Re: [PATCH v3 0/6] Prerequisites for NXP LS104xA SMMU enablement

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Message-ID: <20190531174629.GA6298@infradead.org>
Date:   Fri, 31 May 2019 10:46:30 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        David Miller <davem@...emloft.net>, madalin.bucur@....com,
        netdev@...r.kernel.org, roy.pledge@....com,
        linux-kernel@...r.kernel.org, leoyang.li@....com,
        Joakim.Tjernlund@...inera.com, iommu@...ts.linux-foundation.org,
        camelia.groza@....com, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 0/6] Prerequisites for NXP LS104xA SMMU enablement

On Fri, May 31, 2019 at 06:45:00PM +0100, Robin Murphy wrote:
> Bleh, I'm certainly not keen on formalising any kind of
> dma_to_phys()/dma_to_virt() interface for this. Or are you just proposing
> something like dma_unmap_sorry_sir_the_dog_ate_my_homework() for drivers
> which have 'lost' the original VA they mapped?

Yes, I guess we need that in some form.  I've heard a report the IBM
emca ethernet driver has the same issue, and any SOC with it this
totally blows up dma-debug as they just never properly unmap.