drm/i915/pmu: Fix CPU hotplug with multiple GPUs

Since we keep a driver global mask of online CPUs and base the decision
whether PMU needs to be migrated upon it, we need to make sure the
migration is done for all registered PMUs (so GPUs).

To do this we need to track the current CPU for each PMU and base the
decision on whether to migrate on a comparison between global and local
state.

At the same time, since dynamic CPU hotplug notification slots are a
scarce resource and given how we already register the multi instance type
state, we can and should add multiple instance of the i915 PMU to this
same state and not allocate a new one for every GPU.

v2:
 * Use pr_notice. (Chris)

v3:
 * Handle a nasty interaction where unregistration which triggers a false
   CPU offline event. (Chris)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Suggested-by: Daniel Vetter <daniel.vetter@intel.com> # dynamic slot optimisation
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20201020161144.678668-1-tvrtko.ursulin@linux.intel.com

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
index 366ddfc8df6b..629e19209da0 100644
--- a/drivers/gpu/drm/i915/i915_pci.c
+++ b/drivers/gpu/drm/i915/i915_pci.c
@@ -1129,9 +1129,13 @@ static int __init i915_init(void)
 		return 0;
 	}
 
+	i915_pmu_init();
+
 	err = pci_register_driver(&i915_pci_driver);
-	if (err)
+	if (err) {
+		i915_pmu_exit();
 		return err;
+	}
 
 	i915_perf_sysctl_register();
 	return 0;
@@ -1145,6 +1149,7 @@ static void __exit i915_exit(void)
 	i915_perf_sysctl_unregister();
 	pci_unregister_driver(&i915_pci_driver);
 	i915_globals_exit();
+	i915_pmu_exit();
 }
 
 module_init(i915_init);