linux-kernel - Re: [PATCH kernel v11 34/34] vfio: powerpc/spapr: Support Dynamic DMA windows

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Message-ID: <20150602043719.GG3186@voom.fritz.box>
Date:	Tue, 2 Jun 2015 14:37:19 +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 34/34] vfio: powerpc/spapr: Support Dynamic
 DMA windows

On Fri, May 29, 2015 at 06:44:58PM +1000, Alexey Kardashevskiy wrote:
> This adds create/remove window ioctls to create and remove DMA windows.
> sPAPR defines a Dynamic DMA windows capability which allows
> para-virtualized guests to create additional DMA windows on a PCI bus.
> The existing linux kernels use this new window to map the entire guest
> memory and switch to the direct DMA operations saving time on map/unmap
> requests which would normally happen in a big amounts.
> 
> This adds 2 ioctl handlers - VFIO_IOMMU_SPAPR_TCE_CREATE and
> VFIO_IOMMU_SPAPR_TCE_REMOVE - to create and remove windows.
> Up to 2 windows are supported now by the hardware and by this driver.
> 
> This changes VFIO_IOMMU_SPAPR_TCE_GET_INFO handler to return additional
> information such as a number of supported windows and maximum number
> levels of TCE tables.
> 
> DDW is added as a capability, not as a SPAPR TCE IOMMU v2 unique feature
> as we still want to support v2 on platforms which cannot do DDW for
> the sake of TCE acceleration in KVM (coming soon).
> 
> 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_
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