On 18 October 2016 at 18:57, Andrew Jones <drjo...@redhat.com> wrote: > On Tue, Oct 18, 2016 at 06:07:49PM +0100, Peter Maydell wrote: >> Why do you want to un-property mp_affinity? Eventually it would >> be nice for the machine model to be able to use it to set up >> a specific NUMA configuration. > > I thought about that, but I think we'll want to specify machine > properties; nr_sockets, nr_cores, nr_threads and use the -device > command line for the cpu to specify which socket, which core, > which thread it is. This would be consistent with other architectures > and easily map to the MPIDR & cpu topology hardware descriptions.
I was thinking more about "modelling board X, which we know always has 2xA53 and 4xA57 with these MPIDRs". 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. > Anyway, atm, I don't know of any reason to have the property user- > settable, so it seems safest to keep it hidden until we decide. I agree that it doesn't make sense to let the user mess with it, but it should be available for the board code to read and write. thanks -- PMM
