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

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Date:   Wed, 01 Sep 2021 19:14:24 +0200
From:   "Sven Peter" <sven@...npeter.dev>
To:     "Alyssa Rosenzweig" <alyssa@...enzweig.io>
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



On Tue, Aug 31, 2021, at 23:39, Alyssa Rosenzweig wrote:
> > +	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?

Good point, will do that for the next version.

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

Looks like I dropped an "exactly" there when taking this line from iova.c :)



Thanks,


Sven