On Fri, 30 Nov 2018, Roman Kagan wrote: > On Fri, Nov 30, 2018 at 01:15:11PM +0100, Vitaly Kuznetsov wrote: > > Without 'packed' compiler is free to add optimization paddings and re-order > > structure fields for randomization/optimization. And structures from > > hyperv-tlfs.h are used for hypervisor-guest communication, we need to > > ultimately forbid such practices. > > Note that __packed also reduces the structure alignment to 1, which is > not necessarily what you want. > > E.g. some of these structures are passed by pointer to the hypercall, > which requires its arguments to be 8byte-aligned. I'm also not sure > that passing unaligned argument to [rw]msr is ok, need to double-check.
If you have alignment requirements then you need to express them too. Thanks, tglx