[PATCH 1/7] powerpc: Add interface to get msi region information
R65777 at freescale.com
Wed Oct 9 04:09:50 EST 2013
> -----Original Message-----
> From: joro at 8bytes.org [mailto:joro at 8bytes.org]
> Sent: Tuesday, October 08, 2013 10:32 PM
> To: Bjorn Helgaas
> Cc: Bhushan Bharat-R65777; alex.williamson at redhat.com; benh at kernel.crashing.org;
> galak at kernel.crashing.org; linux-kernel at vger.kernel.org; linuxppc-
> dev at lists.ozlabs.org; linux-pci at vger.kernel.org; agraf at suse.de; Wood Scott-
> B07421; iommu at lists.linux-foundation.org
> Subject: Re: [PATCH 1/7] powerpc: Add interface to get msi region information
> On Tue, Oct 08, 2013 at 10:47:49AM -0600, Bjorn Helgaas wrote:
> > I still have no idea what an "aperture type IOMMU" is, other than that
> > it is "different."
> An aperture based IOMMU is basically any GART-like IOMMU which can only remap a
> small window (the aperture) of the DMA address space. DMA outside of that window
> is either blocked completly or passed through untranslated.
It is completely blocked for Freescale PAMU.
So for this type of iommu what we have to do is to create a MSI mapping just after guest physical address, Example: guest have a 512M of memory then we create window of 1G (because of power of 2 requirement), then we have to FIT MSI just after 512M of guest.
And for that we need
1) to know the physical address of MSI's in interrupt controller (for that this patch was all about of).
2) When guest enable MSI interrupt then we write MSI-address and MSI-DATA in device. The discussion with Alex Williamson is about that interface.
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