linux-kernel - Re: [RFC PATCH v3 3/6] swiotlb: Use restricted DMA pool if available

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Date:   Tue, 12 Jan 2021 15:39:23 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Claire Chang <tientzu@...omium.org>, robh+dt@...nel.org,
        mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        joro@...tes.org, will@...nel.org, frowand.list@...il.com,
        konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
        jgross@...e.com, sstabellini@...nel.org, hch@....de,
        m.szyprowski@...sung.com, robin.murphy@....com
Cc:     grant.likely@....com, xypron.glpk@....de, treding@...dia.com,
        mingo@...nel.org, bauerman@...ux.ibm.com, peterz@...radead.org,
        gregkh@...uxfoundation.org, saravanak@...gle.com,
        rafael.j.wysocki@...el.com, heikki.krogerus@...ux.intel.com,
        andriy.shevchenko@...ux.intel.com, rdunlap@...radead.org,
        dan.j.williams@...el.com, bgolaszewski@...libre.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, iommu@...ts.linux-foundation.org,
        xen-devel@...ts.xenproject.org, tfiga@...omium.org,
        drinkcat@...omium.org
Subject: Re: [RFC PATCH v3 3/6] swiotlb: Use restricted DMA pool if available

On 1/5/21 7:41 PM, Claire Chang wrote:
> Regardless of swiotlb setting, the restricted DMA pool is preferred if
> available.
> 
> The restricted DMA pools provide a basic level of protection against
> the DMA overwriting buffer contents at unexpected times. However, to
> protect against general data leakage and system memory corruption, the
> system needs to provide a way to restrict the DMA to a predefined memory
> region.
> 
> Signed-off-by: Claire Chang <tientzu@...omium.org>

You could probably split this patch into two:

- one that introduces the get_io_tlb_mem() getter, updates all callers
of is_swiotlb_buffer() to gain a 'struct device' argument
- another one that does add support for a non-default swiotlb pool and
adds dev->dma_io_tlb_mem

Other than that, LGTM!
-- 
Florian