linux-kernel - Re: [PATCH v1 4/4] iommu/tegra: gart: Optimize map/unmap

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Date:   Mon, 7 May 2018 09:59:21 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        iommu@...ts.linux-foundation.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 4/4] iommu/tegra: gart: Optimize map/unmap

On Fri, Apr 27, 2018 at 12:02:02PM +0200, Thierry Reding wrote:
> Joerg, I've gone over the git log and header files and I see no mention
> of why the TLB flush interface isn't used for mapping. Do you recall any
> special reasons why the same shouldn't be applied for mapping? Would you
> accept any patches doing this?

Yeah, the reason was that we assumed that only emulated IOMMUs ever need
flushing in the mapping path, and there is no reason to optimize for
that. Especially when a call to iotlb_sync() in the mapping path would
hurt most other users.

Does the tegra-gart actually need it too?



	Joerg