linux-kernel - Re: [PATCH kernel v11 31/34] vfio: powerpc/spapr: powerpc/powernv/ioda2: Use DMA windows API in ownership control

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Date:	Tue, 2 Jun 2015 11:09:21 +1000
From:	David Gibson <david@...son.dropbear.id.au>
To:	Alexey Kardashevskiy <aik@...abs.ru>
Cc:	linuxppc-dev@...ts.ozlabs.org,
	Alex Williamson <alex.williamson@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v11 31/34] vfio: powerpc/spapr:
 powerpc/powernv/ioda2: Use DMA windows API in ownership control

On Fri, May 29, 2015 at 06:44:55PM +1000, Alexey Kardashevskiy wrote:
> Before the IOMMU user (VFIO) would take control over the IOMMU table
> belonging to a specific IOMMU group. This approach did not allow sharing
> tables between IOMMU groups attached to the same container.
> 
> This introduces a new IOMMU ownership flavour when the user can not
> just control the existing IOMMU table but remove/create tables on demand.
> If an IOMMU implements take/release_ownership() callbacks, this lets
> the user have full control over the IOMMU group. When the ownership
> is taken, the platform code removes all the windows so the caller must
> create them.
> Before returning the ownership back to the platform code, VFIO
> unprograms and removes all the tables it created.
> 
> This changes IODA2's onwership handler to remove the existing table
> rather than manipulating with the existing one. From now on,
> iommu_take_ownership() and iommu_release_ownership() are only called
> from the vfio_iommu_spapr_tce driver.
> 
> Old-style ownership is still supported allowing VFIO to run on older
> P5IOC2 and IODA IO controllers.
> 
> No change in userspace-visible behaviour is expected. Since it recreates
> TCE tables on each ownership change, related kernel traces will appear
> more often.
> 
> This adds a pnv_pci_ioda2_setup_default_config() which is called
> when PE is being configured at boot time and when the ownership is
> passed from VFIO to the platform code.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> [aw: for the vfio related changes]
> Acked-by: Alex Williamson <alex.williamson@...hat.com>

Reviewed-by: David Gibson <david@...son.dropbear.id.au>

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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