From: Christoph Hellwig <hch@lst.de>
To: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: linux-kernel@vger.kernel.org, jeremy.linton@arm.com,
iommu@lists.linux-foundation.org,
linux-rpi-kernel@lists.infradead.org,
David Rientjes <rientjes@google.com>,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] dma-pool: use single atomic pool for both DMA zones
Date: Wed, 8 Jul 2020 17:35:09 +0200 [thread overview]
Message-ID: <20200708153509.GA26743@lst.de> (raw)
In-Reply-To: <20200707122804.21262-1-nsaenzjulienne@suse.de>
On Tue, Jul 07, 2020 at 02:28:04PM +0200, Nicolas Saenz Julienne wrote:
> When allocating atomic DMA memory for a device, the dma-pool core
> queries __dma_direct_optimal_gfp_mask() to check which atomic pool to
> use. It turns out the GFP flag returned is only an optimistic guess.
> The pool selected might sometimes live in a zone higher than the
> device's view of memory.
>
> As there isn't a way to grantee a mapping between a device's DMA
> constraints and correct GFP flags this unifies both DMA atomic pools.
> The resulting pool is allocated in the lower DMA zone available, if any,
> so as for devices to always get accessible memory while having the
> flexibility of using dma_pool_kernel for the non constrained ones.
>
> Fixes: c84dc6e68a1d ("dma-pool: add additional coherent pools to map to gfp mask")
> Reported-by: Jeremy Linton <jeremy.linton@arm.com>
> Suggested-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Hmm, this is not what I expected from the previous thread. I thought
we'd just use one dma pool based on runtime available of the zones..
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
David Rientjes <rientjes@google.com>,
linux-rpi-kernel@lists.infradead.org, jeremy.linton@arm.com,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dma-pool: use single atomic pool for both DMA zones
Date: Wed, 8 Jul 2020 17:35:09 +0200 [thread overview]
Message-ID: <20200708153509.GA26743@lst.de> (raw)
In-Reply-To: <20200707122804.21262-1-nsaenzjulienne@suse.de>
On Tue, Jul 07, 2020 at 02:28:04PM +0200, Nicolas Saenz Julienne wrote:
> When allocating atomic DMA memory for a device, the dma-pool core
> queries __dma_direct_optimal_gfp_mask() to check which atomic pool to
> use. It turns out the GFP flag returned is only an optimistic guess.
> The pool selected might sometimes live in a zone higher than the
> device's view of memory.
>
> As there isn't a way to grantee a mapping between a device's DMA
> constraints and correct GFP flags this unifies both DMA atomic pools.
> The resulting pool is allocated in the lower DMA zone available, if any,
> so as for devices to always get accessible memory while having the
> flexibility of using dma_pool_kernel for the non constrained ones.
>
> Fixes: c84dc6e68a1d ("dma-pool: add additional coherent pools to map to gfp mask")
> Reported-by: Jeremy Linton <jeremy.linton@arm.com>
> Suggested-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Hmm, this is not what I expected from the previous thread. I thought
we'd just use one dma pool based on runtime available of the zones..
next prev parent reply other threads:[~2020-07-08 15:35 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 12:28 [PATCH] dma-pool: use single atomic pool for both DMA zones Nicolas Saenz Julienne
2020-07-07 12:28 ` Nicolas Saenz Julienne
2020-07-07 22:08 ` Jeremy Linton
2020-07-07 22:08 ` Jeremy Linton
2020-07-08 10:35 ` Nicolas Saenz Julienne
2020-07-08 10:35 ` Nicolas Saenz Julienne
2020-07-08 15:11 ` Jeremy Linton
2020-07-08 15:11 ` Jeremy Linton
2020-07-08 15:36 ` Christoph Hellwig
2020-07-08 15:36 ` Christoph Hellwig
2020-07-08 16:20 ` Robin Murphy
2020-07-08 16:20 ` Robin Murphy
2020-07-08 15:35 ` Christoph Hellwig [this message]
2020-07-08 15:35 ` Christoph Hellwig
2020-07-08 16:00 ` Nicolas Saenz Julienne
2020-07-08 16:00 ` Nicolas Saenz Julienne
2020-07-08 16:10 ` Christoph Hellwig
2020-07-08 16:10 ` Christoph Hellwig
2020-07-09 21:49 ` David Rientjes via iommu
2020-07-09 21:49 ` David Rientjes
2020-07-10 8:19 ` Nicolas Saenz Julienne
2020-07-10 8:19 ` Nicolas Saenz Julienne
2020-07-08 23:16 ` Jeremy Linton
2020-07-08 23:16 ` Jeremy Linton
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