On 18 October 2016 at 19:45, Eduardo Habkost <ehabk...@redhat.com> wrote: > On Tue, Oct 18, 2016 at 07:12:51PM +0100, Peter Maydell wrote: >> We actually have a concrete instance in the tree at the moment: >> the raspberry pi 2. Specifically hw/arm/bcm2836.c sets the >> mp_affinity for each cpu to 0xF00 | n (where n is the CPUID). >> Currently it's doing that by reaching in and messing with >> the mp_affinity field directly, but really it ought to be >> doing it by setting a property on the CPU, and what it >> wants isn't somethnig that can be expressed with a simple >> nr_sockets/nr_cores/etc scheme. > > I am confused now. I thought QOM properties were meant for > user-visible and/or user-configurable data. I assumed that if > it's only meant to be used by C code inside QEMU, C functions > and/or C struct fields were the way to go.
Lots of stuff in a device's C struct is strictly internal and not to be messed with. I thought that QOM properties were essentially how a device defined its public (and typically settable-only-once) config knobs. QOM properties shouldn't be user-facing (read: stable, required to be backwards-compatible) interface in general because we don't really want to tie ourselves down that much. In fact almost all our QOM objects are not usefully user-facing at all. thanks -- PMM
