On Thu, 28 Feb 2019 12:19:22 +0000 Jean-Philippe Brucker <jean-philippe.bruc...@arm.com> wrote:
> On 27/02/2019 21:41, Jacob Pan wrote: > > On Tue, 26 Feb 2019 12:17:43 +0100 > > Joerg Roedel <j...@8bytes.org> wrote: > > > >> Hi Jean-Philippe, > >> > >> Thanks for the patch! I think this is getting close to be applied > >> after the next merge window. > >> > >> On Wed, Feb 20, 2019 at 02:27:59PM +0000, Jean-Philippe Brucker > >> wrote: > >>> +int iommu_sva_bind_device(struct device *dev, struct mm_struct > >>> *mm, int *pasid, > >>> + iommu_mm_exit_handler_t mm_exit, void > >>> *drvdata) > >> > >> I think we are better of with introducing a sva-bind handle which > >> can be used to extend and further configure the binding done with > >> this function. > >> > >> How about a 'struct iommu_sva' with an iommu-private definition > >> that is returned by this function: > >> > >> struct iommu_sva *iommu_sva_bind_device(struct device *dev, > >> struct mm_struct > >> *mm); > > Just trying to understand how to use this API. > > So if we bind the same mm to two different devices, we should get > > two different iommu_sva handle, right? > > Yes, the iommu_sva handle is the bond between one mm and one device, > so you will get two different handles. > > > I think intel-svm still needs a flag argument for supervisor pasid > > etc. Other than that, I think both interface should work for vt-d. > > Is supervisor PASID still needed now that we have auxiliary domains, > and now that VT-d supports nested IOVA? You could have private kernel > address spaces through auxiliary domains, or simply use DMA API as > usual with PASID#0. I've been reluctant to make that feature common > because it looks risky - gives full access to the kernel address > space to devices and no notification on mapping change. > It is still in the VT-d spec. Ashok will be able to answer this better :) > > Another question is that for nested SVA, we will need to bind guest > > mm. Do you think we should try to reuse this or have it separate? I > > am working on a separate API for now. > > I also think it should be separate. That bind() operation is performed > on an auxiliary domain, I guess? > yes the 2nd level is retrieved from aux domain for mdev, but for pdev, 2nd level comes from rid2pasid/default domain. > >> and the corresponding unbind function: > >> > >> int iommu_sva_unbind_device(struct iommu_sva* *handle); > >> > >> (Btw, does this need to return and int? Can unbinding fail?). > >> > >> With that in place we can implement and extentable API base on the > >> handle: > >> > >> int iommu_sva_get_pasid(struct iommu_sva *handle); > > If multiple bind to the same mm gets multiple handles, this API > > should retrieve the same pasid for different handle? > > Yes > > > Just curious why making > > the handle private instead of returning the pasid value in the > > handle? > > I don't have a strong objection against that. One reason to have an > accessor is that the PASID is freed on mm_exit, so until the device > driver calls unbind(), the PASID contained in the handle is stale (and > the accessor returns PASID_INVALID). But that's a bit pedantic, the > device driver should know that the handle is stale since it got > notified of it. Having an accessor might also help tracking uses of > the handle in the kernel, and make future API modifications easier. > make sense. > Thanks, > Jean > > >> void iommu_sva_set_exit_handler(struct iommu_sva *handle, > >> iommu_mm_exit_handler_t > >> mm_exit); > >> > >> I think at least the AMD IOMMU driver needs more call-backs like a > >> handler that is invoked when a fault can not be resolved. And there > >> might be others in the future, putting them all in the parameter > >> list of the bind function doesn't scale well. > >> > > > >> Regards, > >> > >> Joerg > > > > > [Jacob Pan] _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
