On Mon, 20 Oct 2014 20:14:53 +0200 Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > On 10/18/2014 06:28 PM, Dave Hansen wrote: > > > Currently it is an all or nothing thing, but for a future change we might want to just > > > tag the guest memory instead of the complete user address space. > > > > I think it's a bad idea to reserve a flag for potential future use. If > > you_need_ it in the future, let's have the discussion then. For now, I > > think it should probably just be stored in the mm somewhere. > > I agree with Dave (I thought I disagreed, but I changed my mind while > writing down my thoughts). Just define mm_forbids_zeropage in > arch/s390/include/asm, and make it return mm->context.use_skey---with a > comment explaining how this is only for processes that use KVM, and then > only for guests that use storage keys. The mm_forbids_zeropage() sure will work for now, but I think a vma flag is the better solution. This is analog to VM_MERGEABLE or VM_NOHUGEPAGE, the best solution would be to only mark those vmas that are mapped to the guest. That we have not found a way to do that yet in a sensible way does not change the fact that "no-zero-page" is a per-vma property, no? But if you insist we go with the mm_forbids_zeropage() until we find a clever way to distinguish the guest vmas from the qemu ones. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>