linux-kernel - Re: [PATCH kernel v11 18/34] vfio: powerpc/spapr/iommu/powernv/ioda2: Rework IOMMU ownership control

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Message-ID: <20150601063444.GK22789@voom.redhat.com>
Date:	Mon, 1 Jun 2015 16:34:44 +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 18/34] vfio:
 powerpc/spapr/iommu/powernv/ioda2: Rework IOMMU ownership control

On Fri, May 29, 2015 at 06:44:42PM +1000, Alexey Kardashevskiy wrote:
> This adds tce_iommu_take_ownership() and tce_iommu_release_ownership
> which call in a loop iommu_take_ownership()/iommu_release_ownership()
> for every table on the group. As there is just one now, no change in
> behaviour is expected.
> 
> At the moment the iommu_table struct has a set_bypass() which enables/
> disables DMA bypass on IODA2 PHB. This is exposed to POWERPC IOMMU code
> which calls this callback when external IOMMU users such as VFIO are
> about to get over a PHB.
> 
> The set_bypass() callback is not really an iommu_table function but
> IOMMU/PE function. This introduces a iommu_table_group_ops struct and
> adds take_ownership()/release_ownership() callbacks to it which are
> called when an external user takes/releases control over the IOMMU.
> 
> This replaces set_bypass() with ownership callbacks as it is not
> necessarily just bypass enabling, it can be something else/more
> so let's give it more generic name.
> 
> The callbacks is implemented for IODA2 only. Other platforms (P5IOC2,
> IODA1) will use the old iommu_take_ownership/iommu_release_ownership API.
> The following patches will replace iommu_take_ownership/
> iommu_release_ownership calls in IODA2 with full IOMMU table release/
> create.
> 
> As we here and touching bypass control, this removes
> pnv_pci_ioda2_setup_bypass_pe() as it does not do much
> more compared to pnv_pci_ioda2_set_bypass. This moves tce_bypass_base
> initialization to pnv_pci_ioda2_setup_dma_pe.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> [aw: for the vfio related changes]
> Acked-by: Alex Williamson <alex.williamson@...hat.com>
> Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.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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