linux-kernel - Re: [PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option

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Date:   Mon, 19 Dec 2016 14:57:00 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Konrad Rzeszutek Wilk <konrad@...nok.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        David Vrabel <david.vrabel@...rix.com>,
        Juergen Gross <jgross@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option

Hi Konrad,

On Mon, Dec 19, 2016 at 2:38 PM, Konrad Rzeszutek Wilk
<konrad@...nok.org> wrote:
> On Fri, Dec 16, 2016 at 02:28:42PM +0100, Geert Uytterhoeven wrote:
>> On architectures like arm64, swiotlb is tied intimately to the core
>> architecture DMA support. In addition, ZONE_DMA cannot be disabled.
>>
>> To aid debugging and catch devices not supporting DMA to memory outside
>> the 32-bit address space, add a kernel command line option
>> "swiotlb=noforce", which disables the use of bounce buffers.
>> If specified, trying to map memory that cannot be used with DMA will
>> fail, and a rate-limited warning will be printed.
>>
>> Note that io_tlb_nslabs is set to 1, which is the minimal supported
>> value.
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
>
> What is this based on? I can't apply it on my latest that I had
> sent to Linus?

I rebased it on last Friday's linux-next, due to the recent move of
kernel-parameters.txt.
All the rest should be identical to your linux-next branch.

> Could you rebase this one please on:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb.git stable/for-linus-4.9

That one indeed doesn't have the move of kernel-parameters.txt.

> Or if alternatively that does not - then please rebase it on
> b5cab0da75c292ffa0fbd68dd2c820066b2842de

However, my series already applies cleanly with git am on top of
that commit?

Please let me know what to do. Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds