sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/drivers/video/fbdev/carminefb.h b/drivers/video/fbdev/carminefb.h
new file mode 100644
index 000000000..c9825481d
--- /dev/null
+++ b/drivers/video/fbdev/carminefb.h
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef CARMINE_CARMINE_H
+#define CARMINE_CARMINE_H
+
+#define CARMINE_MEMORY_BAR	2
+#define CARMINE_CONFIG_BAR	3
+
+#define MAX_DISPLAY	2
+#define CARMINE_DISPLAY_MEM	(800 * 600 * 4)
+#define CARMINE_TOTAL_DISPLAY_MEM	(CARMINE_DISPLAY_MEM * MAX_DISPLAY)
+
+#define CARMINE_USE_DISPLAY0	(1 << 0)
+#define CARMINE_USE_DISPLAY1	(1 << 1)
+
+/*
+ * This values work on the eval card. Custom boards may use different timings,
+ * here an example :)
+ */
+
+/* DRAM initialization values */
+#ifdef CONFIG_FB_CARMINE_DRAM_EVAL
+
+#define CARMINE_DFLT_IP_CLOCK_ENABLE		(0x03ff)
+#define CARMINE_DFLT_IP_DCTL_ADD		(0x05c3)
+#define CARMINE_DFLT_IP_DCTL_MODE		(0x0121)
+#define CARMINE_DFLT_IP_DCTL_EMODE		(0x8000)
+#define CARMINE_DFLT_IP_DCTL_SET_TIME1		(0x4749)
+#define CARMINE_DFLT_IP_DCTL_SET_TIME2		(0x2a22)
+#define CARMINE_DFLT_IP_DCTL_REFRESH		(0x0042)
+#define CARMINE_DFLT_IP_DCTL_STATES		(0x0003)
+#define CARMINE_DFLT_IP_DCTL_RESERVE0		(0x0020)
+#define CARMINE_DFLT_IP_DCTL_FIFO_DEPTH		(0x000f)
+#define CARMINE_DFLT_IP_DCTL_RESERVE2		(0x0000)
+#define CARMINE_DFLT_IP_DCTL_DDRIF1		(0x6646)
+#define CARMINE_DFLT_IP_DCTL_DDRIF2		(0x0055)
+#define CARMINE_DFLT_IP_DCTL_MODE_AFT_RST	(0x0021)
+#define CARMINE_DFLT_IP_DCTL_STATES_AFT_RST	(0x0002)
+#define CARMINE_DFLT_IP_DCTL_IO_CONT0		(0x0555)
+#define CARMINE_DFLT_IP_DCTL_IO_CONT1		(0x0555)
+#define CARMINE_DCTL_DLL_RESET			(1)
+#endif
+
+#ifdef CONFIG_CARMINE_DRAM_CUSTOM
+
+#define CARMINE_DFLT_IP_CLOCK_ENABLE		(0x03ff)
+#define CARMINE_DFLT_IP_DCTL_ADD		(0x03b2)
+#define CARMINE_DFLT_IP_DCTL_MODE		(0x0161)
+#define CARMINE_DFLT_IP_DCTL_EMODE		(0x8000)
+#define CARMINE_DFLT_IP_DCTL_SET_TIME1		(0x2628)
+#define CARMINE_DFLT_IP_DCTL_SET_TIME2		(0x1a09)
+#define CARMINE_DFLT_IP_DCTL_REFRESH		(0x00fe)
+#define CARMINE_DFLT_IP_DCTL_STATES		(0x0003)
+#define CARMINE_DFLT_IP_DCTL_RESERVE0		(0x0020)
+#define CARMINE_DFLT_IP_DCTL_FIFO_DEPTH		(0x000f)
+#define CARMINE_DFLT_IP_DCTL_RESERVE2		(0x0000)
+#define CARMINE_DFLT_IP_DCTL_DDRIF1		(0x0646)
+#define CARMINE_DFLT_IP_DCTL_DDRIF2		(0x55aa)
+#define CARMINE_DFLT_IP_DCTL_MODE_AFT_RST	(0x0061)
+#define CARMINE_DFLT_IP_DCTL_STATES_AFT_RST	(0x0002)
+#define CARMINE_DFLT_IP_DCTL_IO_CONT0		(0x0555)
+#define CARMINE_DFLT_IP_DCTL_IO_CONT1		(0x0555)
+#define CARMINE_DCTL_DLL_RESET			(1)
+#endif
+
+#endif