On Tue, Oct 06, 2015 at 10:26:34AM +0000, Bhushan Bharat wrote: [...] > > > > I'm certainly not interested in applying an maintaining an interim solution that > > isn't the right one. It seems like VFIO is too involved in this process in your > > example. On x86 we have per vector isolation and the only thing we're > > missing is reporting back of the region used by MSI vectors as reserved IOVA > > space (but it's standard on x86, so an x86 VM user will never use it for IOVA). > > I remember you mentioned that there is no problem when running an x86 guest on an x86 host. But it will interesting when running a non-x86 VMs on an x86 host or non-VM userspace use of VFIO though. > > > In your model, the MSI IOVA space is programmable, > > Yes, on PowerPC and ARM-SMMU case also we have to create mapping with an IOVA. First question is which IOVA to be used, and we added the reserved iova ioctl for same. > > Second problem is we needed an msi-page physical address for setting up iommu-mapping, and so we needed to reserve an msi-page. I did this for PowerPC but not in a generic extension in msi-driver and will look the code a bit more details on adding an interface to reserve an msi-page or get a shared msi-page with allow-unsafe-interrupt. Sorry, I'm far from familiar with how x86 does interrupt handling and I know very little of PCIe and MSIs, so please allow me to ask some stupid questions: What does an msi-page physical address mean? > > Third problem is to report the reserved IOVA to be used for MSI vectors for the given set of devices (devices in a vfio-group). What do MSI vectors mean in this context? Is this a Linux kernel construct, something tied to PCIe, something tied to the interrupt controller, or? In the case of ARM, AFAIU, you have a single doorbell register per ITS and devices can write to this register with their device id and the eventid. So it's a register in a page somewhere. Now, what is the problem you don't understand with ARM here? > > Mark/Christopher, > I am not an expert in this area so I might have to understand that code. If you think you can give solution to 2nd and 3rd problem quickly then please let me know. > I don't really understand what you're asking, but if you can educate me on the concepts above I may be able to offer some advice. Thanks, -Christoffer -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
