From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Christoph Hellwig <hch@lst.de>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
Lu Baolu <baolu.lu@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Joerg Roedel <joro@8bytes.org>,
Robin Murphy <robin.murphy@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device
Date: Tue, 24 Mar 2020 14:05:54 +1100 [thread overview]
Message-ID: <ffce1af6-a215-dee8-7b5c-2111f43accfd@ozlabs.ru> (raw)
In-Reply-To: <20200323172256.GB31269@lst.de>
On 24/03/2020 04:22, Christoph Hellwig wrote:
> On Mon, Mar 23, 2020 at 09:07:38PM +0530, Aneesh Kumar K.V wrote:
>>
>> This is what I was trying, but considering I am new to DMA subsystem, I
>> am not sure I got all the details correct. The idea is to look at the
>> cpu addr and see if that can be used in direct map fashion(is
>> bus_dma_limit the right restriction here?) if not fallback to dynamic
>> IOMMU mapping.
>
> I don't think we can throw all these complications into the dma
> mapping code. At some point I also wonder what the point is,
> especially for scatterlist mappings, where the iommu can coalesce.
This is for persistent memory which you can DMA to/from but yet it does
not appear in the system as a normal memory and therefore requires
special handling anyway (O_DIRECT or DAX, I do not know the exact
mechanics). All other devices in the system should just run as usual,
i.e. use 1:1 mapping if possible.
--
Alexey
WARNING: multiple messages have this Message-ID (diff)
From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Christoph Hellwig <hch@lst.de>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Joerg Roedel <joro@8bytes.org>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org,
Robin Murphy <robin.murphy@arm.com>,
Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device
Date: Tue, 24 Mar 2020 14:05:54 +1100 [thread overview]
Message-ID: <ffce1af6-a215-dee8-7b5c-2111f43accfd@ozlabs.ru> (raw)
In-Reply-To: <20200323172256.GB31269@lst.de>
On 24/03/2020 04:22, Christoph Hellwig wrote:
> On Mon, Mar 23, 2020 at 09:07:38PM +0530, Aneesh Kumar K.V wrote:
>>
>> This is what I was trying, but considering I am new to DMA subsystem, I
>> am not sure I got all the details correct. The idea is to look at the
>> cpu addr and see if that can be used in direct map fashion(is
>> bus_dma_limit the right restriction here?) if not fallback to dynamic
>> IOMMU mapping.
>
> I don't think we can throw all these complications into the dma
> mapping code. At some point I also wonder what the point is,
> especially for scatterlist mappings, where the iommu can coalesce.
This is for persistent memory which you can DMA to/from but yet it does
not appear in the system as a normal memory and therefore requires
special handling anyway (O_DIRECT or DAX, I do not know the exact
mechanics). All other devices in the system should just run as usual,
i.e. use 1:1 mapping if possible.
--
Alexey
WARNING: multiple messages have this Message-ID (diff)
From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Christoph Hellwig <hch@lst.de>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device
Date: Tue, 24 Mar 2020 14:05:54 +1100 [thread overview]
Message-ID: <ffce1af6-a215-dee8-7b5c-2111f43accfd@ozlabs.ru> (raw)
In-Reply-To: <20200323172256.GB31269@lst.de>
On 24/03/2020 04:22, Christoph Hellwig wrote:
> On Mon, Mar 23, 2020 at 09:07:38PM +0530, Aneesh Kumar K.V wrote:
>>
>> This is what I was trying, but considering I am new to DMA subsystem, I
>> am not sure I got all the details correct. The idea is to look at the
>> cpu addr and see if that can be used in direct map fashion(is
>> bus_dma_limit the right restriction here?) if not fallback to dynamic
>> IOMMU mapping.
>
> I don't think we can throw all these complications into the dma
> mapping code. At some point I also wonder what the point is,
> especially for scatterlist mappings, where the iommu can coalesce.
This is for persistent memory which you can DMA to/from but yet it does
not appear in the system as a normal memory and therefore requires
special handling anyway (O_DIRECT or DAX, I do not know the exact
mechanics). All other devices in the system should just run as usual,
i.e. use 1:1 mapping if possible.
--
Alexey
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2020-03-24 3:06 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 14:16 generic DMA bypass flag v2 Christoph Hellwig
2020-03-20 14:16 ` Christoph Hellwig
2020-03-20 14:16 ` Christoph Hellwig
2020-03-20 14:16 ` [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device Christoph Hellwig
2020-03-20 14:16 ` Christoph Hellwig
2020-03-20 14:16 ` Christoph Hellwig
2020-03-20 15:02 ` Greg Kroah-Hartman
2020-03-20 15:02 ` Greg Kroah-Hartman
2020-03-20 15:02 ` Greg Kroah-Hartman
2020-03-23 1:28 ` Alexey Kardashevskiy
2020-03-23 1:28 ` Alexey Kardashevskiy
2020-03-23 1:28 ` Alexey Kardashevskiy
2020-03-23 8:37 ` Christoph Hellwig
2020-03-23 8:37 ` Christoph Hellwig
2020-03-23 8:37 ` Christoph Hellwig
2020-03-23 8:50 ` Christoph Hellwig
2020-03-23 8:50 ` Christoph Hellwig
2020-03-23 8:50 ` Christoph Hellwig
2020-03-23 15:37 ` Aneesh Kumar K.V
2020-03-23 15:37 ` Aneesh Kumar K.V
2020-03-23 15:37 ` Aneesh Kumar K.V
2020-03-23 17:22 ` Christoph Hellwig
2020-03-23 17:22 ` Christoph Hellwig
2020-03-23 17:22 ` Christoph Hellwig
2020-03-24 3:05 ` Alexey Kardashevskiy [this message]
2020-03-24 3:05 ` Alexey Kardashevskiy
2020-03-24 3:05 ` Alexey Kardashevskiy
2020-03-24 6:30 ` Aneesh Kumar K.V
2020-03-24 6:30 ` Aneesh Kumar K.V
2020-03-24 6:30 ` Aneesh Kumar K.V
2020-03-24 7:55 ` Christoph Hellwig
2020-03-24 7:55 ` Christoph Hellwig
2020-03-24 7:55 ` Christoph Hellwig
2020-03-24 7:54 ` Christoph Hellwig
2020-03-24 7:54 ` Christoph Hellwig
2020-03-24 7:54 ` Christoph Hellwig
2020-03-25 4:51 ` Alexey Kardashevskiy
2020-03-25 4:51 ` Alexey Kardashevskiy
2020-03-25 4:51 ` Alexey Kardashevskiy
2020-03-25 8:37 ` Christoph Hellwig
2020-03-25 8:37 ` Christoph Hellwig
2020-03-25 8:37 ` Christoph Hellwig
2020-03-26 1:26 ` Alexey Kardashevskiy
2020-03-26 1:26 ` Alexey Kardashevskiy
2020-03-26 1:26 ` Alexey Kardashevskiy
2020-04-03 8:38 ` Alexey Kardashevskiy
2020-04-03 8:38 ` Alexey Kardashevskiy
2020-04-03 8:38 ` Alexey Kardashevskiy
2020-04-06 11:50 ` Christoph Hellwig
2020-04-06 11:50 ` Christoph Hellwig
2020-04-06 11:50 ` Christoph Hellwig
2020-04-06 13:25 ` Alexey Kardashevskiy
2020-04-06 13:25 ` Alexey Kardashevskiy
2020-04-06 13:25 ` Alexey Kardashevskiy
2020-04-06 17:17 ` Christoph Hellwig
2020-04-06 17:17 ` Christoph Hellwig
2020-04-06 17:17 ` Christoph Hellwig
2020-04-07 10:12 ` Alexey Kardashevskiy
2020-04-07 10:12 ` Alexey Kardashevskiy
2020-04-07 10:12 ` Alexey Kardashevskiy
2020-04-14 6:21 ` Alexey Kardashevskiy
2020-04-14 6:21 ` Alexey Kardashevskiy
2020-04-14 6:21 ` Alexey Kardashevskiy
2020-04-14 6:30 ` Christoph Hellwig
2020-04-14 6:30 ` Christoph Hellwig
2020-04-14 6:30 ` Christoph Hellwig
2020-03-23 8:58 ` Alexey Kardashevskiy
2020-03-23 8:58 ` Alexey Kardashevskiy
2020-03-23 8:58 ` Alexey Kardashevskiy
2020-03-23 17:20 ` Christoph Hellwig
2020-03-23 17:20 ` Christoph Hellwig
2020-03-23 17:20 ` Christoph Hellwig
2020-03-24 3:37 ` Alexey Kardashevskiy
2020-03-24 3:37 ` Alexey Kardashevskiy
2020-03-24 3:37 ` Alexey Kardashevskiy
2020-03-24 4:55 ` Alexey Kardashevskiy
2020-03-24 4:55 ` Alexey Kardashevskiy
2020-03-24 4:55 ` Alexey Kardashevskiy
2020-03-24 7:52 ` Christoph Hellwig
2020-03-24 7:52 ` Christoph Hellwig
2020-03-24 7:52 ` Christoph Hellwig
2020-03-23 12:14 ` Robin Murphy
2020-03-23 12:14 ` Robin Murphy
2020-03-23 12:14 ` Robin Murphy
2020-03-23 12:55 ` Christoph Hellwig
2020-03-23 12:55 ` Christoph Hellwig
2020-03-23 12:55 ` Christoph Hellwig
2020-03-20 14:16 ` [PATCH 2/2] powerpc: use the generic dma_ops_bypass mode Christoph Hellwig
2020-03-20 14:16 ` Christoph Hellwig
2020-03-20 14:16 ` Christoph Hellwig
-- strict thread matches above, loose matches on Subject: below --
2020-03-24 9:39 [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to, struct device Christian Zigotzky
2019-11-13 13:37 generic DMA bypass flag Christoph Hellwig
2019-11-13 13:37 ` [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device Christoph Hellwig
2019-11-13 13:37 ` Christoph Hellwig
2019-11-13 13:37 ` Christoph Hellwig
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