linux-kernel - Re: [PATCH v3] swiotlb: Make SWIOTLB_NO

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Message-ID: <20210324084250.GA4474@lst.de>
Date:   Wed, 24 Mar 2021 09:42:50 +0100
From:   Christoph Hellwig <hch@....de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        "open list:SWIOTLB SUBSYSTEM" <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH v3] swiotlb: Make SWIOTLB_NO_FORCE perform no allocation

On Mon, Mar 22, 2021 at 06:53:49PM -0700, Florian Fainelli wrote:
> When SWIOTLB_NO_FORCE is used, there should really be no allocations of
> default_nslabs to occur since we are not going to use those slabs. If a
> platform was somehow setting swiotlb_no_force and a later call to
> swiotlb_init() was to be made we would still be proceeding with
> allocating the default SWIOTLB size (64MB), whereas if swiotlb=noforce
> was set on the kernel command line we would have only allocated 2KB.
> 
> This would be inconsistent and the point of initializing default_nslabs
> to 1, was intended to allocate the minimum amount of memory possible, so
> simply remove that minimal allocation period.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@....de>