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Date:   Tue, 14 Sep 2021 17:30:46 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Jan Beulich <jbeulich@suse.com>
Cc:     Roman Skakun <rm.skakun@gmail.com>,
        Andrii Anisov <andrii_anisov@epam.com>,
        Roman Skakun <roman_skakun@epam.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Maciej W. Rozycki" <macro@orcam.me.uk>,
        Muchun Song <songmuchun@bytedance.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Mike Rapoport <rppt@kernel.org>, Will Deacon <will@kernel.org>,
        xen-devel@lists.xenproject.org, linux-mips@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org
Subject: Re: [PATCH] swiotlb: set IO TLB segment size via cmdline
Message-ID: <20210914153046.GB815@lst.de>
References: <20210914151016.3174924-1-Roman_Skakun@epam.com> <7c04db79-7de1-93ff-0908-9bad60a287b9@suse.com>
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On Tue, Sep 14, 2021 at 05:29:07PM +0200, Jan Beulich wrote:
> I'm not convinced the swiotlb use describe there falls under "intended
> use" - mapping a 1280x720 framebuffer in a single chunk? (As an aside,
> the bottom of this page is also confusing, as following "Then we can
> confirm the modified swiotlb size in the boot log:" there is a log
> fragment showing the same original size of 64Mb.

It doesn't.  We also do not add hacks to the kernel for whacky out
of tree modules.