linux-kernel - Re: [PATCH v2 0/8] Support IOMMU page sizes larger than the CPU page size

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Date:   Tue, 31 Aug 2021 17:32:07 -0400
From:   Alyssa Rosenzweig <alyssa@...enzweig.io>
To:     Sven Peter <sven@...npeter.dev>
Cc:     iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Arnd Bergmann <arnd@...nel.org>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Alexander Graf <graf@...zon.com>,
        Hector Martin <marcan@...can.st>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/8] Support IOMMU page sizes larger than the CPU page
 size

> Some background: On the Apple M1 the IOMMUs are hardwired to only support 16 KB pages.
> We'd still like to boot Linux with 4KB pages though because that's what most distros
> ship these days. This patch series adds support for that setup to the IOMMU DMA API.

This isn't just a distro issue -- efficient x86_64 emulation will rely
on 4KB as well (Rosetta, FEX, ...). Telling distros to use 16KB kernels
for Apple parts is just kicking the can down the road -- we want this
series even for kernels we build ourselves.