Thread (17 messages) 17 messages, 4 authors, 2021-08-03

Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC

From: Joerg Roedel <joro@8bytes.org>
Date: 2021-06-25 13:19:04
Also in: linux-arm-kernel, linux-arm-msm, linux-iommu, linux-mmc, linux-pci, lkml

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
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