From: Christoph Hellwig <hch@lst.de>
To: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc: Alexander Duyck <alexander.duyck@gmail.com>,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>,
"alexander.h.duyck@linux.intel.com"
<alexander.h.duyck@linux.intel.com>,
"open list:INTEL IOMMU (VT-d)" <iommu@lists.linux-foundation.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
"open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)"
<linuxppc-dev@lists.ozlabs.org>,
LKML <linux-kernel@vger.kernel.org>,
Guenter Roeck <linux@roeck-us.net>,
Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] dma-direct: Fix return value of dma_direct_supported
Date: Thu, 13 Dec 2018 20:58:31 +0100 [thread overview]
Message-ID: <20181213195831.GA15478@lst.de> (raw)
In-Reply-To: <ebe0d4aa-5f37-cc40-4a80-cfe499d5b8e4@amd.com>
On Thu, Dec 13, 2018 at 07:45:57PM +0000, Lendacky, Thomas wrote:
> So I think this needs to be __phys_to_dma() here. I only recently got a
> system that had a device where the driver only supported 32-bit DMA and
> found that when SME is active this returns 0 and causes the driver to fail
> to initialize. This is because the SME encryption bit (bit 47) is part of
> the check when using phys_to_dma(). During actual DMA when SME is active,
> bounce buffers will be used for anything that can't meet the 48-bit
> requirement. But for this test, using __phys_to_dma() should give the
> desired results, right?
>
> If you agree with this, I'll submit a patch to make the change. I missed
> this in 4.19, so I'll need to submit something to stable, too. The only
> issue there is the 4.20 fix won't apply cleanly to 4.19.
Yes, please send a patch. Please make sure it includes a code comment
that explains why the __-prefixed version is used.
prev parent reply other threads:[~2018-12-13 19:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-03 23:48 [PATCH] dma-direct: Fix return value of dma_direct_supported Alexander Duyck
2018-10-04 11:25 ` Robin Murphy
2018-10-04 15:13 ` Alexander Duyck
2018-10-05 7:17 ` Christoph Hellwig
2018-12-13 19:45 ` Lendacky, Thomas
2018-12-13 19:58 ` Christoph Hellwig [this message]
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