Add a new bus method to fetch device-specific CPU sets.

bus_get_cpus() returns a specified set of CPUs for a device.  It accepts
an enum for the second parameter that indicates the type of cpuset to
request.  Currently two valus are supported:

 - LOCAL_CPUS (on x86 this returns all the CPUs in the package closest to
   the device when DEVICE_NUMA is enabled)
 - INTR_CPUS (like LOCAL_CPUS but only returns 1 SMT thread for each core)

For systems that do not support NUMA (or if it is not enabled in the kernel
config), LOCAL_CPUS fails with EINVAL.  INTR_CPUS is mapped to 'all_cpus'
by default.  The idea is that INTR_CPUS should always return a valid set.

Device drivers which want to use per-CPU interrupts should start using
INTR_CPUS instead of simply assigning interrupts to all available CPUs.
In the future we may wish to add tunables to control the policy of
INTR_CPUS (e.g. should it be local-only or global, should it ignore
SMT threads or not).

The x86 nexus driver exposes the internal set of interrupt CPUs from the
the x86 interrupt code via INTR_CPUS.

The ACPI bus driver and PCI bridge drivers use _PXM to return a suitable
LOCAL_CPUS set when _PXM exists and DEVICE_NUMA is enabled.  They also and
the global INTR_CPUS set from the nexus driver with the per-domain set from
_PXM to generate a local INTR_CPUS set for child devices.

Compared to the r298933, this version uses 'struct _cpuset' in
<sys/bus.h> instead of 'cpuset_t' to avoid requiring <sys/param.h>
(<sys/_cpuset.h> still requires <sys/param.h> for MAXCPU even though
<sys/_bitset.h> does not after recent changes).

1 files changed, 18 insertions, 0 deletions

diff --git a/sys/kern/bus_if.m b/sys/kern/bus_if.m
index 56673a4..f0115e8 100644
--- a/sys/kern/bus_if.m
+++ b/sys/kern/bus_if.m
@@ -731,3 +731,21 @@ METHOD int get_domain {
 	device_t	_child;
 	int		*_domain;
 } DEFAULT bus_generic_get_domain;
+
+/**
+ * @brief Request a set of CPUs
+ *
+ * @param _dev		the bus device
+ * @param _child	the child device
+ * @param _op		type of CPUs to request
+ * @param _setsize	the size of the set passed in _cpuset
+ * @param _cpuset	a pointer to a cpuset to receive the requested
+ *			set of CPUs
+ */
+METHOD int get_cpus {
+	device_t	_dev;
+	device_t	_child;
+	enum cpu_sets	_op;
+	size_t		_setsize;
+	cpuset_t	*_cpuset;
+} DEFAULT bus_generic_get_cpus;