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Date:   Fri, 25 Jun 2021 15:18:58 +0200
From:   Joerg Roedel <joro@8bytes.org>
To:     Douglas Anderson <dianders@chromium.org>
Cc:     will@kernel.org, robin.murphy@arm.com, bjorn.andersson@linaro.org,
        ulf.hansson@linaro.org, adrian.hunter@intel.com,
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        quic_c_gdjako@quicinc.com, saravanak@google.com,
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        linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org,
        iommu@lists.linux-foundation.org, sonnyrao@chromium.org,
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        Jordan Crouse <jordan@cosmicpenguin.net>,
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        Nicolin Chen <nicoleotsuka@gmail.com>,
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        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Vlastimil Babka <vbabka@suse.cz>,
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        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC
Message-ID: <YNXXwvuErVnlHt+s@8bytes.org>
References: <20210624171759.4125094-1-dianders@chromium.org>
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Hi Douglas,

On Thu, Jun 24, 2021 at 10:17:56AM -0700, Douglas Anderson wrote:
> The goal of this patch series is to get better SD/MMC performance on
> Qualcomm eMMC controllers and in generally nudge us forward on the
> path of allowing some devices to be in strict mode and others to be in
> non-strict mode.

So if I understand it right, this patch-set wants a per-device decision
about setting dma-mode to strict vs. non-strict.

I think we should get to the reason why strict mode is used by default
first. Is the default on ARM platforms to use iommu-strict mode by
default and if so, why?

The x86 IOMMUs use non-strict mode by default (yes, it is a security
trade-off).

Regards,

	Joerg