x86/intel_rdt: Ensure a CPU remains online for the region's pseudo-locking sequence
The user triggers the creation of a pseudo-locked region when writing the requested schemata to the schemata resctrl file. The pseudo-locking of a region is required to be done on a CPU that is associated with the cache on which the pseudo-locked region will reside. In order to run the locking code on a specific CPU, the needed CPU has to be selected and ensured to remain online during the entire locking sequence. At this time, the cpu_hotplug_lock is not taken during the pseudo-lock region creation and it is thus possible for a CPU to be selected to run the pseudo-locking code and then that CPU to go offline before the thread is able to run on it. Fix this by ensuring that the cpu_hotplug_lock is taken while the CPU on which code has to run needs to be controlled. Since the cpu_hotplug_lock is always taken before rdtgroup_mutex the lock order is maintained. Fixes: e0bdfe8e ("x86/intel_rdt: Support creation/removal of pseudo-locked region") Signed-off-by: NReinette Chatre <reinette.chatre@intel.com> Signed-off-by: NBorislav Petkov <bp@suse.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: gavin.hindman@intel.com Cc: jithu.joseph@intel.com Cc: stable <stable@vger.kernel.org> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/b7b17432a80f95a1fa21a1698ba643014f58ad31.1544476425.git.reinette.chatre@intel.com
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