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From: Christoph Hellwig <hch@lst.de>
To: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Halil Pasic <pasic@linux.ibm.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>,
	Lucas Stach <l.stach@pengutronix.de>
Subject: Re: Regression due to d98849aff879 (dma-direct: handle DMA_ATTR_NO_KERNEL_MAPPING in common code)
Date: Tue, 6 Aug 2019 18:07:09 +0200	[thread overview]
Message-ID: <20190806160709.GA25586@lst.de> (raw)
In-Reply-To: <5bd42e33-8077-ea23-a9f3-c575db4edada@amd.com>

On Tue, Aug 06, 2019 at 03:59:40PM +0000, Lendacky, Thomas wrote:
> As long as two different cookie types (page pointer for encrypted DMA
> and virtual address returned from page_address() for unencrypted DMA)
> is ok. I'm just not familiar with how the cookie is used in any other
> functions, if at all.

DMA_ATTR_NO_KERNEL_MAPPING is intended for memory never used in the
kernel, either because it is just a buffer for device that are too cheap
to enough dram, or because it is a buffer for userspace to device
communication that the kernel just mediates.
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iommu@lists.linux-foundation.org
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Lucas Stach <l.stach@pengutronix.de>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Thiago Jung Bauermann <bauerman@linux.ibm.com>,
	Halil Pasic <pasic@linux.ibm.com>
Subject: Re: Regression due to d98849aff879 (dma-direct: handle DMA_ATTR_NO_KERNEL_MAPPING in common code)
Date: Tue, 6 Aug 2019 18:07:09 +0200	[thread overview]
Message-ID: <20190806160709.GA25586@lst.de> (raw)
In-Reply-To: <5bd42e33-8077-ea23-a9f3-c575db4edada@amd.com>

On Tue, Aug 06, 2019 at 03:59:40PM +0000, Lendacky, Thomas wrote:
> As long as two different cookie types (page pointer for encrypted DMA
> and virtual address returned from page_address() for unencrypted DMA)
> is ok. I'm just not familiar with how the cookie is used in any other
> functions, if at all.

DMA_ATTR_NO_KERNEL_MAPPING is intended for memory never used in the
kernel, either because it is just a buffer for device that are too cheap
to enough dram, or because it is a buffer for userspace to device
communication that the kernel just mediates.

  reply	other threads:[~2019-08-06 16:07 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-06  9:13 Regression due to d98849aff879 (dma-direct: handle DMA_ATTR_NO_KERNEL_MAPPING in common code) Lucas Stach
2019-08-06  9:13 ` Lucas Stach
2019-08-06 11:33 ` Christoph Hellwig
2019-08-06 11:33   ` Christoph Hellwig
2019-08-06 12:20   ` Lucas Stach
2019-08-06 12:20     ` Lucas Stach
2019-08-06 13:38   ` Lendacky, Thomas
2019-08-06 13:38     ` Lendacky, Thomas
2019-08-06 14:04     ` Christoph Hellwig
2019-08-06 14:04       ` Christoph Hellwig
2019-08-06 14:06       ` Lucas Stach
2019-08-06 14:06         ` Lucas Stach
2019-08-06 14:18         ` Lendacky, Thomas
2019-08-06 14:18           ` Lendacky, Thomas
2019-08-06 15:46           ` Christoph Hellwig
2019-08-06 15:46             ` Christoph Hellwig
2019-08-06 15:59             ` Lendacky, Thomas
2019-08-06 15:59               ` Lendacky, Thomas
2019-08-06 16:07               ` Christoph Hellwig [this message]
2019-08-06 16:07                 ` Christoph Hellwig
2019-08-06 15:44         ` Christoph Hellwig
2019-08-06 15:44           ` Christoph Hellwig
2019-08-07 15:24           ` Lucas Stach
2019-08-07 15:24             ` Lucas Stach
2019-08-08  7:48             ` Christoph Hellwig
2019-08-08  7:48               ` Christoph Hellwig

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