On Mon, Sep 14, 2009 at 12:08:55PM -0400, Gregory Haskins wrote: > Michael S. Tsirkin wrote: > > On Fri, Sep 11, 2009 at 12:00:21PM -0400, Gregory Haskins wrote: > >> FWIW: VBUS handles this situation via the "memctx" abstraction. IOW, > >> the memory is not assumed to be a userspace address. Rather, it is a > >> memctx-specific address, which can be userspace, or any other type > >> (including hardware, dma-engine, etc). As long as the memctx knows how > >> to translate it, it will work. > > > > How would permissions be handled? > > Same as anything else, really. Read on for details. > > > it's easy to allow an app to pass in virtual addresses in its own address space. > > Agreed, and this is what I do. > > The guest always passes its own physical addresses (using things like > __pa() in linux). This address passed is memctx specific, but generally > would fall into the category of "virtual-addresses" from the hosts > perspective. > > For a KVM/AlacrityVM guest example, the addresses are GPAs, accessed > internally to the context via a gfn_to_hva conversion (you can see this > occuring in the citation links I sent) > > For Ira's example, the addresses would represent a physical address on > the PCI boards, and would follow any kind of relevant rules for > converting a "GPA" to a host accessible address (even if indirectly, via > a dma controller). So vbus can let an application access either its own virtual memory or a physical memory on a PCI device. My question is, is any application that's allowed to do the former also granted rights to do the later? > > But we can't let the guest specify physical addresses. > > Agreed. Neither your proposal nor mine operate this way afaict. > > HTH > > Kind Regards, > -Greg > -- 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
