linux-kernel - Re: [PATCH v2 6/8] iommu: Move IOMMU pagesize check to attach

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Date:   Tue, 31 Aug 2021 17:39:35 -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 6/8] iommu: Move IOMMU pagesize check to attach_device

> +	if ((1 << __ffs(domain->pgsize_bitmap)) > PAGE_SIZE) {

Not a fan of this construction. Could you assign `(1 <<
__ffs(domain->pgsize_bitmap))` to an appropriately named temporary (e.g
min_io_pgsize) so it's clearer what's going on?

> +		pr_warn("IOMMU page size cannot represent CPU pages.\n");

"Represent" how?