From: Christoph Hellwig <hch@lst.de>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
iommu@lists.linux-foundation.org, Christoph Hellwig <hch@lst.de>,
linux-kernel@vger.kernel.org
Subject: Re: Regression due to d98849aff879 (dma-direct: handle DMA_ATTR_NO_KERNEL_MAPPING in common code)
Date: Tue, 6 Aug 2019 13:33:18 +0200 [thread overview]
Message-ID: <20190806113318.GA20215@lst.de> (raw)
In-Reply-To: <1565082809.2323.24.camel@pengutronix.de>
On Tue, Aug 06, 2019 at 11:13:29AM +0200, Lucas Stach wrote:
> Hi Christoph,
>
> I just found a regression where my NVMe device is no longer able to set
> up its HMB.
>
> After subject commit dma_direct_alloc_pages() is no longer initializing
> dma_handle properly when DMA_ATTR_NO_KERNEL_MAPPING is set, as the
> function is now returning too early.
>
> Now this could easily be fixed by adding the phy_to_dma translation to
> the NO_KERNEL_MAPPING code path, but I'm not sure how this stuff
> interacts with the memory encryption stuff set up later in the
> function, so I guess this should be looked at by someone with more
> experience with this code than me.
There is not much we can do about the memory encryption case here,
as that requires a kernel address to mark the memory as unencrypted.
So the obvious trivial fix is probably the right one:
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 59bdceea3737..c49120193309 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -135,6 +135,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
if (!PageHighMem(page))
arch_dma_prep_coherent(page, size);
/* return the page pointer as the opaque cookie */
+ *dma_handle = phys_to_dma(dev, page_to_phys(page));
return page;
}
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next prev parent reply other threads:[~2019-08-06 11:33 UTC|newest]
Thread overview: 13+ 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 11:33 ` Christoph Hellwig [this message]
2019-08-06 12:20 ` Lucas Stach
2019-08-06 13:38 ` Lendacky, Thomas
2019-08-06 14:04 ` Christoph Hellwig
2019-08-06 14:06 ` Lucas Stach
2019-08-06 14:18 ` Lendacky, Thomas
2019-08-06 15:46 ` Christoph Hellwig
2019-08-06 15:59 ` Lendacky, Thomas
2019-08-06 16:07 ` Christoph Hellwig
2019-08-06 15:44 ` Christoph Hellwig
2019-08-07 15:24 ` Lucas Stach
2019-08-08 7:48 ` Christoph Hellwig
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