Hi James, On 9/10/25 21:42, James Morse wrote: > Because an MSC can only by accessed from the CPUs in its cpu-affinity > set we need to be running on one of those CPUs to probe the MSC > hardware. > > Do this work in the cpuhp callback. Probing the hardware will only > happen before MPAM is enabled, walk all the MSCs and probe those we can > reach that haven't already been probed as each CPU's online call is made. > > This adds the low-level MSC register accessors. > > Once all MSCs reported by the firmware have been probed from a CPU in > their respective cpu-affinity set, the probe-time cpuhp callbacks are > replaced. The replacement callbacks will ultimately need to handle > save/restore of the runtime MSC state across power transitions, but for > now there is nothing to do in them: so do nothing. > > The architecture's context switch code will be enabled by a static-key, > this can be set by mpam_enable(), but must be done from process context, > not a cpuhp callback because both take the cpuhp lock. > Whenever a new MSC has been probed, the mpam_enable() work is scheduled > to test if all the MSCs have been probed. If probing fails, mpam_disable() > is scheduled to unregister the cpuhp callbacks and free memory. > > CC: Lecopzer Chen <lecopzerc@xxxxxxxxxx> > Signed-off-by: James Morse <james.morse@xxxxxxx> > --- > Changes since v1: > * Removed register bounds check. If the firmware tables are wrong the > resulting translation fault should be enough to debug this. > * Removed '&' in front of a function pointer. > * Pulled mpam_disable() into this patch. > * Disable mpam when probing fails to avoid extra work on broken platforms. > * Added mpam_disbale_reason as there are now two non-debug reasons for this > to happen. Looks good to me. Reviewed-by: Ben Horgan <ben.horgan@xxxxxxx> Thanks, Ben
