Anthony Liguori wrote: > Avi Kivity wrote: >> [EMAIL PROTECTED] wrote: >> >>> From: Ben-Ami Yassour <[EMAIL PROTECTED]> >>> >>> Enable a guest to access a device's memory mapped I/O regions directly. >>> Userspace sends the mmio regions that the guest can access. On the >>> first >>> page fault for an access to an mmio address the host translates the >>> gva to hpa, >>> and updates the sptes. >>> >>> >> >> Can you explain why you're not using the regular memory slot >> mechanism? i.e. have userspace mmap(/dev/mem) and create a memslot >> containing that at the appropriate guest physical address? >> > > /dev/mem is often restricted in what memory can be mapped.
Please elaborate. > However, we can't add something like this to KVM that allows arbitrary > HPA's to be mapped into a guest from userspace. This is just as bad > as /dev/mem and is going to upset a lot of people. Device assignment is as rootish as you get. > > > Regardless of whether we can use /dev/mem, I think we should introduce > a new char device anyway. We only need to mmap() MMIO regions which > are mapped by the PCI bus, presumably, the kernel should know about > these mappings. The driver should only allow mappings that are valid > for a particular PCI device such that it cannot be abused to map > arbitrary regions of memory into a guest. Bonus points if it can > validate that there isn't a valid Linux driver loaded for the given > PCI device. This is a very good idea. The interface exposed would be the same as /dev/mem, so any kvm modifications to get /dev/mem working would be applicable to /dev/pci/*, no? -- Any sufficiently difficult bug is indistinguishable from a feature. ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
