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? -- Vitaly
