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From: "hch@lst.de" <hch@lst.de>
To: Thomas Hellstrom <thellstrom@vmware.com>
Cc: "thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"hch@lst.de" <hch@lst.de>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"christian.koenig@amd.com" <christian.koenig@amd.com>
Subject: Re: [PATCH 2/2] dma-mapping: force unencryped devices are always addressing limited
Date: Thu, 28 Nov 2019 16:36:46 +0100
Message-ID: <20191128153646.GA29430@lst.de> (raw)
In-Reply-To: <MN2PR05MB6141B6D7E28A146EBF9CE79FA1470@MN2PR05MB6141.namprd05.prod.outlook.com>

On Thu, Nov 28, 2019 at 08:02:16AM +0000, Thomas Hellstrom wrote:
> > We have a hard time handling that in generic code.  Do we have any
> > good use case for SWIOTLB_FORCE not that we have force_dma_unencrypted?
> > I'd love to be able to get rid of it..
> >
> IIRC the justification for it is debugging. Drivers that don't do
> syncing correctly or have incorrect assumptions of initialization of DMA
> memory will not work properly when SWIOTLB is forced. We recently found
> a vmw_pvscsi device flaw that way...

Ok. I guess debugging is reasonable.  Although that means I need
to repsin this quite a bit as I now need a callout to dma_direct.
I'll respin it in the next days.
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Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-27 14:40 make dma_addressing_limited work for memory encryption setups Christoph Hellwig
2019-11-27 14:40 ` [PATCH 1/2] dma-mapping: move dma_addressing_limited out of line Christoph Hellwig
2019-11-27 17:13   ` Matthew Wilcox
2019-11-27 14:40 ` [PATCH 2/2] dma-mapping: force unencryped devices are always addressing limited Christoph Hellwig
2019-11-27 18:22   ` Thomas Hellstrom via iommu
2019-11-28  7:51     ` hch
2019-11-28  8:02       ` Thomas Hellstrom via iommu
2019-11-28 15:36         ` hch [this message]
2019-12-04 13:03 make dma_addressing_limited work for memory encryption setups v2 Christoph Hellwig
2019-12-04 13:03 ` [PATCH 2/2] dma-mapping: force unencryped devices are always addressing limited Christoph Hellwig
2019-12-06 14:10   ` Thomas Hellstrom via iommu

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