Re: [PATCH v9 12/13] KVM: PPC: Add support for IOMMU in-kernel handling

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Sep 05, 2013 at 02:05:09PM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2013-09-03 at 13:53 +0300, Gleb Natapov wrote:
> > > Or supporting all IOMMU links (and leaving emulated stuff as is) in on
> > > "device" is the last thing I have to do and then you'll ack the patch?
> > > 
> > I am concerned more about API here. Internal implementation details I
> > leave to powerpc experts :)
> 
> So Gleb, I want to step in for a bit here.
> 
> While I understand that the new KVM device API is all nice and shiny and that this
> whole thing should probably have been KVM devices in the first place (had they
> existed or had we been told back then), the point is, the API for handling
> HW IOMMUs that Alexey is trying to add is an extension of an existing mechanism
> used for emulated IOMMUs.
> 
> The internal data structure is shared, and fundamentally, by forcing him to
> use that new KVM device for the "new stuff", we create a oddball API with
> an ioctl for one type of iommu and a KVM device for the other, which makes
> the implementation a complete mess in the kernel (and you should care :-)
> 
Is it unfixable mess? Even if Alexey will do what you suggested earlier?

  - Convert *both* existing TCE objects to the new
      KVM_CREATE_DEVICE, and have some backward compat code for the old one.

The point is implementation usually can be changed, but for API it is
much harder to do so.

> So for something completely new, I would tend to agree with you. However, I
> still think that for this specific case, we should just plonk-in the original
> ioctl proposed by Alexey and be done with it.
> 
Do you think this is the last extension to IOMMU code, or we will see
more and will use same justification to continue adding ioctls?

--
			Gleb.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>




[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]