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Subject: Re: [PATCH RFC v1 2/6] swiotlb: convert variables to arrays
To:     Christoph Hellwig <hch@lst.de>,
        Dongli Zhang <dongli.zhang@oracle.com>
Cc:     dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        iommu@lists.linux-foundation.org, linux-mips@vger.kernel.org,
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        linuxppc-dev@lists.ozlabs.org, nouveau@lists.freedesktop.org,
        x86@kernel.org, xen-devel@lists.xenproject.org,
        linux-kernel@vger.kernel.org, adrian.hunter@intel.com,
        akpm@linux-foundation.org, benh@kernel.crashing.org,
        bskeggs@redhat.com, bhelgaas@google.com, bp@alien8.de,
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        daniel@ffwll.ch, airlied@linux.ie, hpa@zytor.com, mingo@kernel.org,
        mingo@redhat.com, jani.nikula@linux.intel.com,
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        konrad.wilk@oracle.com, m.szyprowski@samsung.com,
        matthew.auld@intel.com, mpe@ellerman.id.au, rppt@kernel.org,
        paulus@samba.org, peterz@infradead.org, rodrigo.vivi@intel.com,
        sstabellini@kernel.org, bauerman@linux.ibm.com,
        tsbogend@alpha.franken.de, tglx@linutronix.de,
        ulf.hansson@linaro.org, joe.jin@oracle.com,
        thomas.lendacky@amd.com, Claire Chang <tientzu@chromium.org>
References: <20210203233709.19819-1-dongli.zhang@oracle.com>
 <20210203233709.19819-3-dongli.zhang@oracle.com>
 <20210204072947.GA29812@lst.de>
From:   Robin Murphy <robin.murphy@arm.com>
Message-ID: <b46ddefe-d91a-fa6a-0e0d-cf1edc343c2e@arm.com>
Date:   Thu, 4 Feb 2021 11:49:23 +0000
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On 2021-02-04 07:29, Christoph Hellwig wrote:
> On Wed, Feb 03, 2021 at 03:37:05PM -0800, Dongli Zhang wrote:
>> This patch converts several swiotlb related variables to arrays, in
>> order to maintain stat/status for different swiotlb buffers. Here are
>> variables involved:
>>
>> - io_tlb_start and io_tlb_end
>> - io_tlb_nslabs and io_tlb_used
>> - io_tlb_list
>> - io_tlb_index
>> - max_segment
>> - io_tlb_orig_addr
>> - no_iotlb_memory
>>
>> There is no functional change and this is to prepare to enable 64-bit
>> swiotlb.
> 
> Claire Chang (on Cc) already posted a patch like this a month ago,
> which looks much better because it actually uses a struct instead
> of all the random variables.

Indeed, I skimmed the cover letter and immediately thought that this 
whole thing is just the restricted DMA pool concept[1] again, only from 
a slightly different angle.

Robin.

[1] 
https://lore.kernel.org/linux-iommu/20210106034124.30560-1-tientzu@chromium.org/