On Tue, 03 Feb 2015 16:22:32 +0100 Paolo Bonzini <pbonz...@redhat.com> wrote:
> > > On 03/02/2015 16:16, Thomas Huth wrote: > > Actually, I'd prefer to keep the "virtual" in the defines for the type > > of operation below: When it comes to s390 storage keys, we likely might > > need some calls for reading and writing to physical memory, too. Then > > we could simply extend this ioctl instead of inventing a new one. > > Can you explain why it is necessary to read/write physical addresses > from user space? In the case of QEMU, I'm worried that you would have > to invent your own memory read/write APIs that are different from > everything else. > > On real s390 zPCI, does bus-master DMA update storage keys? Ah, I was not thinking about bus-mastering/DMA here: AFAIK there are some CPU instructions that access a parameter block in physical memory, for example the SCLP instruction (see hw/s390x/sclp.c) - it's already doing a cpu_physical_memory_read and ..._write for the parameters. However, I haven't checked yet whether it is also supposed to touch the storage keys, so if not, we also might be fine without the ioctls for reading/writing to physical memory. > >> Not really true, as you don't check it. So "It is not used by KVM with > >> the currently defined set of flags" is a better explanation. > > > > ok ... and maybe add "should be set to zero" ? > > If you don't check it, it is misleading to document this. True... so I'll omit that. Thomas
