From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
To: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Subject: Re: [PATCH] iommu/dma-iommu: properly respect configured address space size
Date: Thu, 10 Nov 2016 16:59:39 +0100 [thread overview]
Message-ID: <20161110155938.GI2078@8bytes.org> (raw)
In-Reply-To: <68e7a18b-739e-b73e-eacf-3cb6c1bd279a-5wv7dgnIgG8@public.gmane.org>
On Tue, Nov 08, 2016 at 11:37:23AM +0000, Robin Murphy wrote:
> TBH I've been pondering ripping the size stuff out of dma-iommu, as it
> all stems from me originally failing to understand what dma_32bit_pfn is
> actually for.
The point of dma_32bit_pfn is to allocate dma-address below 4G by
default. This is a performance optimization so that even devices capable
of 64bit DMA are using SAC by default instead of DAC.
Since it is the goal to share a dma-iommu implemenation between
architectures, I would rather prefer not to rip this stuff out.
Joerg
WARNING: multiple messages have this Message-ID (diff)
From: joro@8bytes.org (Joerg Roedel)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] iommu/dma-iommu: properly respect configured address space size
Date: Thu, 10 Nov 2016 16:59:39 +0100 [thread overview]
Message-ID: <20161110155938.GI2078@8bytes.org> (raw)
In-Reply-To: <68e7a18b-739e-b73e-eacf-3cb6c1bd279a@arm.com>
On Tue, Nov 08, 2016 at 11:37:23AM +0000, Robin Murphy wrote:
> TBH I've been pondering ripping the size stuff out of dma-iommu, as it
> all stems from me originally failing to understand what dma_32bit_pfn is
> actually for.
The point of dma_32bit_pfn is to allocate dma-address below 4G by
default. This is a performance optimization so that even devices capable
of 64bit DMA are using SAC by default instead of DAC.
Since it is the goal to share a dma-iommu implemenation between
architectures, I would rather prefer not to rip this stuff out.
Joerg
WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] iommu/dma-iommu: properly respect configured address space size
Date: Thu, 10 Nov 2016 16:59:39 +0100 [thread overview]
Message-ID: <20161110155938.GI2078@8bytes.org> (raw)
In-Reply-To: <68e7a18b-739e-b73e-eacf-3cb6c1bd279a@arm.com>
On Tue, Nov 08, 2016 at 11:37:23AM +0000, Robin Murphy wrote:
> TBH I've been pondering ripping the size stuff out of dma-iommu, as it
> all stems from me originally failing to understand what dma_32bit_pfn is
> actually for.
The point of dma_32bit_pfn is to allocate dma-address below 4G by
default. This is a performance optimization so that even devices capable
of 64bit DMA are using SAC by default instead of DAC.
Since it is the goal to share a dma-iommu implemenation between
architectures, I would rather prefer not to rip this stuff out.
Joerg
next prev parent reply other threads:[~2016-11-10 15:59 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20161107130625eucas1p2dd23c07010b4f3eddb6c6540ed802246@eucas1p2.samsung.com>
2016-11-07 13:06 ` [PATCH] iommu/dma-iommu: properly respect configured address space size Marek Szyprowski
2016-11-07 13:06 ` Marek Szyprowski
2016-11-07 13:06 ` Marek Szyprowski
[not found] ` <1478523973-8828-1-git-send-email-m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-11-08 11:37 ` Robin Murphy
2016-11-08 11:37 ` Robin Murphy
2016-11-08 11:37 ` Robin Murphy
[not found] ` <68e7a18b-739e-b73e-eacf-3cb6c1bd279a-5wv7dgnIgG8@public.gmane.org>
2016-11-08 13:41 ` Marek Szyprowski
2016-11-08 13:41 ` Marek Szyprowski
2016-11-08 13:41 ` Marek Szyprowski
[not found] ` <8286728f-fab3-8179-5215-e156da426244-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-11-08 14:44 ` Robin Murphy
2016-11-08 14:44 ` Robin Murphy
2016-11-08 14:44 ` Robin Murphy
[not found] ` <d215c05c-b922-4bee-a2dc-695669a801f6-5wv7dgnIgG8@public.gmane.org>
2016-11-08 14:53 ` Marek Szyprowski
2016-11-08 14:53 ` Marek Szyprowski
2016-11-08 14:53 ` Marek Szyprowski
2016-11-10 14:08 ` Robin Murphy
2016-11-10 14:08 ` Robin Murphy
2016-11-10 15:59 ` Joerg Roedel [this message]
2016-11-10 15:59 ` Joerg Roedel
2016-11-10 15:59 ` Joerg Roedel
[not found] ` <20161110155938.GI2078-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
2016-11-10 16:17 ` Robin Murphy
2016-11-10 16:17 ` Robin Murphy
2016-11-10 16:17 ` Robin Murphy
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