RE: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU (PAMU)

[Varun Sethi]

> -----Original Message-----
> From: iommu-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx [mailto:iommu-
> bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Alex Williamson
> Sent: Thursday, November 21, 2013 12:17 AM
> To: Bhushan Bharat-R65777
> Cc: linux-pci@xxxxxxxxxxxxxxx; agraf@xxxxxxx; Yoder Stuart-B08248; Wood
> Scott-B07421; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx;
> linuxppc-dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU
> (PAMU)
> 
> On Tue, 2013-11-19 at 10:47 +0530, Bharat Bhushan wrote:
> > From: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>
> >
> > PAMU (FSL IOMMU) has a concept of primary window and subwindows.
> > Primary window corresponds to the complete guest iova address space
> > (including MSI space), with respect to IOMMU_API this is termed as
> > geometry. IOVA Base of subwindow is determined from the number of
> > subwindows (configurable using iommu API).
> > MSI I/O page must be within the geometry and maximum supported
> > subwindows, so MSI IO-page is setup just after guest memory iova space.
> >
> > So patch 1/9-4/9(inclusive) are for defining the interface to get:
> >   - Number of MSI regions (which is number of MSI banks for powerpc)
> >   - MSI-region address range: Physical page which have the
> >     address/addresses used for generating MSI interrupt
> >     and size of the page.
> >
> > Patch 5/9-7/9(inclusive) is defining the interface of setting up MSI
> > iova-base for a msi region(bank) for a device. so that when
> > msi-message will be composed then this configured iova will be used.
> > Earlier we were using iommu interface for getting the configured iova
> > which was not currect and Alex Williamson suggeested this type of
> interface.
> >
> > patch 8/9 moves some common functions in a separate file so that these
> > can be used by FSL_PAMU implementation (next patch uses this).
> > These will be used later for iommu-none implementation. I believe we
> > can do more of this but will take step by step.
> >
> > Finally last patch actually adds the support for FSL-PAMU :)
> 
> Patches 1-3: msi_get_region needs to return an error an error (probably
> -EINVAL) if called on a path where there's no backend implementation.
> Otherwise the caller doesn't know that the data in the region pointer
> isn't valid.
> 
> Patches 5&6: same as above for msi_set_iova, return an error if no
> backend implementation.
> 
> Patch 7: Why does fsl_msi_del_iova_device bother to return anything if
> it's always zero?  Return -ENODEV when not found?
> 
> Patch 9:
> 
> vfio_handle_get_attr() passes random kernel data back to userspace in the
> event of iommu_domain_get_attr() error.
> 
> vfio_handle_set_attr(): I don't see any data validation happening, is
> iommu_domain_set_attr() really that safe?
[Sethi Varun-B16395] The parameter validation can be left to the lower level iommu driver. The attribute could be specific to a given hardware.

-Varun

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