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Date:   Fri, 19 Mar 2021 19:59:36 +0000
From:   Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To:     Christoph Hellwig <hch@lst.de>, xen-devel@lists.xensource.com,
        sstabellini@kernel.org
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        linux-arm-kernel@lists.infradead.org,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        "open list:SWIOTLB SUBSYSTEM" <iommu@lists.linux-foundation.org>,
        open list <linux-kernel@vger.kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Mike Rapoport <rppt@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>, opendmb@gmail.com
Subject: Re: [PATCH] ARM: Qualify enabling of swiotlb_init()
Message-ID: <20210319195929.GA1346384@konrad-char-us-oracle-com.allregionaliads.osdevelopmeniad.oraclevcn.com>
References: <20210319040333.183827-1-f.fainelli@gmail.com>
 <20210319130731.GB2624@lst.de>
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On Fri, Mar 19, 2021 at 02:07:31PM +0100, Christoph Hellwig wrote:
> On Thu, Mar 18, 2021 at 09:03:33PM -0700, Florian Fainelli wrote:
> >  #ifdef CONFIG_ARM_LPAE
> > +	if (swiotlb_force == SWIOTLB_FORCE ||
> > +	    max_pfn > arm_dma_pfn_limit)
> 
> Does arm_dma_pfn_limit do the right thing even with the weirdest
> remapping ranges?  Maybe a commen here would be useful.
> 
> > +		swiotlb_init(1);
> > +	else
> > +		swiotlb_force = SWIOTLB_NO_FORCE;
> 
> Konrad: what do you think of setting swiotlb_force to SWIOTLB_NO_FORCE
> and only switching it to SWIOTLB_NORMAL when swiotlb_init* is called?
> That kind makes more sense than forcing the callers to do it.
> 
> While we're at it, I think swiotlb_force should probably be renamed to
> swiotlb_mode or somethng like that.

swiotlb_mode sounds good.

Also it got me thinking - ARM on Xen at some point was a bit strange, so not sure how
the logic works here, Stefano?