CMA in AMD IOMMU driver

CMA in AMD IOMMU driver

[Sathyavathi M]

Dear All,

This mail regarding the below communication about CMA in AMD IOMMU driver.

On Mon, Feb 02, 2015 at 10:35:36AM -0700, Alex Williamson wrote:
> [cc +joerg]
> 
> On Mon, 2015-02-02 at 11:01 -0500, Mark Hounschell wrote:
> >  From what I understand of CMA, and it seems provable to me, is that 
> > dma_alloc_coherent allocates my 8MB buffer from CMA defined on the 
> > cmdline. Without CMA specified on the cmdline, dma_alloc_coherent 
> > definitely fails to allocate an 8MB contiguous buffer. From what I've 
> > read about it, it is supposed to transparently "just work" when 
> > dma_alloc_coherent is used?
> 
> Yes, if you're running with the software iotlb (aka. bounce buffers),
> then dma_ops->alloc is x86_swiotlb_alloc_coherent(), which calls
> dma_generic_alloc_coherent(), which attempts to use CMA via
> dma_alloc_from_contiguous().
> 
> If you look at the same path with AMD-Vi, dma_ops->alloc is
> amd_iommu.c:alloc_coherent(), which simply uses __get_free_pages() to
> allocate the buffer.  I don't see any CMA integration along that path.
> If you were using Intel VT-d, then the buffer is again allocated with
> dma_alloc_from_contiguous() and should use CMA.  This was added in
> kernel v3.16, but no corresponding AMD-Vi change was added.  Joerg, this
> might be an easily fixed oversight.

Right, CMA is not yet integrated in the AMD IOMMU driver, nobody asked
fot it until now :) I will add that fall-back there for big allocations.


	Joerg


Has CMA been added in AMD IOMMU driver, If yes which version of kernel has it.


Thanks in Advance.
 
Regards,
Sathya
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Re: CMA in AMD IOMMU driver

[Christoph Hellwig]

Toms conversion of the AMD IOMMU driver to use dma-iommu adds CMA
support :)
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RE: Re: CMA in AMD IOMMU driver

[Sathyavathi M]

Dear Christoph,

Thanks for the reply.
can you please let me know which kernel has it?


Thanks,
Sathya 
 
--------- Original Message ---------
Sender : Christoph Hellwig <hch@infradead.org>
Date   : 2019-06-26 12:28 (GMT+5:30)
Title  : Re: CMA in AMD IOMMU driver
To : Sathyavathi M<sathya.m@samsung.com>
CC : null<iommu@lists.linux-foundation.org>
 
Toms conversion of the AMD IOMMU driver to use dma-iommu adds CMA
support :)
 
 
Regards,
Sathya
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RE: RE: Re: CMA in AMD IOMMU driver

[Sathyavathi M]

I tried to apply the patch (AMD IOMMU driver to use dma-iommu) to linux kerenl 5.1.15 but it gives me some errors. 
Downloaded the patch from https://patchwork.ozlabs.org/patch/1096015/

Is this the right way im doing?

Please let me know.

Thanks,
Sathya 
 
--------- Original Message ---------
Sender : Sathyavathi M <sathya.m@samsung.com> Engineer/Host Software /SSIR/Samsung Electronics
Date   : 2019-06-26 15:21 (GMT+5:30)
Title  : RE: Re: CMA in AMD IOMMU driver
To : null<hch@infradead.org>
CC : null<iommu@lists.linux-foundation.org>
 
Dear Christoph,
 
Thanks for the reply.
can you please let me know which kernel has it?
 
 
Thanks,
Sathya 
 
--------- Original Message ---------
Sender : Christoph Hellwig <hch@infradead.org>
Date   : 2019-06-26 12:28 (GMT+5:30)
Title  : Re: CMA in AMD IOMMU driver
To : Sathyavathi M<sathya.m@samsung.com>
CC : null<iommu@lists.linux-foundation.org>
 
Toms conversion of the AMD IOMMU driver to use dma-iommu adds CMA
support :)
 
 
Regards,
Sathya
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Regards,
Sathya
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RE: Re: CMA in AMD IOMMU driver

[Sathyavathi M]

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