linux-kernel - Re: [PATCH v4 0/6] normalize IOMMU dma mode boot options

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Message-ID: <5CAABD03.9000301@huawei.com>
Date:   Mon, 8 Apr 2019 11:16:19 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Hanjun Guo <guohanjun@...wei.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        John Garry <john.garry@...wei.com>,
        "Robin Murphy" <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>,
        "Joerg Roedel" <joro@...tes.org>, Jonathan Corbet <corbet@....net>,
        linux-doc <linux-doc@...r.kernel.org>,
        Sebastian Ott <sebott@...ux.ibm.com>,
        "Gerald Schaefer" <gerald.schaefer@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        David Woodhouse <dwmw2@...radead.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        x86 <x86@...nel.org>, linux-ia64 <linux-ia64@...r.kernel.org>
Subject: Re: [PATCH v4 0/6] normalize IOMMU dma mode boot options



On 2019/4/8 9:14, Hanjun Guo wrote:
> Hi Zhen,
> 
> On 2019/4/7 20:41, Zhen Lei wrote:
>> As Robin Murphy's suggestion:
>> "It's also not necessarily obvious to the user how this interacts with
>> IOMMU_DEFAULT_PASSTHROUGH, so if we really do go down this route, maybe it
>> would be better to refactor the whole lot into a single selection of something
>> like IOMMU_DEFAULT_MODE anyway."
>>
>> In this version, I tried to normalize the IOMMU dma mode boot options for all
>> ARCHs. When IOMMU is enabled, there are 3 dma modes: paasthrough(bypass),
>> lazy(mapping but defer the IOTLB invalidation), strict. But currently each
>> ARCHs defined their private boot options, different with each other. For
>> example, to enable/disable "passthrough", ARM64 use iommu.passthrough=1/0,
>> X86 use iommu=pt/nopt, PPC/POWERNV use iommu=nobypass.
>>
>>
>> Zhen Lei (6):
>>   iommu: use iommu.dma_mode to replace iommu.passthrough and
>>     iommu.strict
>>   iommu: keep dma mode build options consistent with cmdline options
>>   iommu: add iommu_default_dma_mode_get() helper
>>   s390/pci: use common boot option iommu.dma_mode
>>   powernv/iommu: use common boot option iommu.dma_mode
>>   x86/iommu: use common boot option iommu.dma_mode
> 
> This will break systems using boot options as now, and I think
> this is unacceptable. If you want to do so, just introduce iommu.dma_mode
> on top of those iommu boot options with dma mode boot options unchanged,
> and iommu.dma_mode is for all archs but compatible with them.

I just changed the boot options name, but keep the function no change. I added
all related maintainers/supporters in the "to=" list, maybe we can disuss this.
Should I add some "obsoleted" warnings for old options and keep them for a while?
But I think this kind of thing is best done in one go.

> 
> Thanks
> Hanjun
> 
> 
> .
> 

-- 
Thanks!
BestRegards