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

[Joerg Roedel]

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