On Thu, 29 Nov 2018, Vitaly Kuznetsov wrote: > Nadav Amit <nadav.amit@xxxxxxxxx> writes: > > >> On Nov 28, 2018, at 5:07 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > >> > >> On Wed, 28 Nov 2018, Vitaly Kuznetsov wrote: > >> > >>> Nadav Amit <nadav.amit@xxxxxxxxx> writes: > >>> > >>>> On a different note: how come all of the hyper-v structs are not marked > >>>> with the “packed" attribute? > >>> > >>> "packed" should not be needed with proper padding; I vaguely remember > >>> someone (from x86@?) arguing _against_ "packed". > >> > >> Packed needs to be used, when describing fixed format data structures in > >> hardware or other ABIs, so the compiler cannot put alignment holes into > >> them. > >> > >> Using packed for generic data structures might result in suboptimal layouts > >> and prevents layout randomization. > > > > Right, I forgot about the structs randomization. So at least for it, the > > attribute should be needed. > > > > Not sure when randomization.s used but Hyper-V drivers will of course be > utterly broken with it. > > > To prevent conflicts, I think that this series should also add the > > attribute in a first patch, which would be tagged for stable. > > As the patchset doesn't add new definitions and as Paolo already queued > it I'd go with a follow-up patch adding "packed" to all hyperv-tlfs.h > structures. The question is how to avoid conflicts when Linus will be > merging this. We can do: > - Topic branch in kvm > - Send the patch to x86, make topic branch and reabse kvm > - Send the patch to kvm > - ... ? > > Paolo/Thomas, what would be your preference? As Paolo already has it, just route it through his tree please. Thanks, tglx
