Commit 0f5650a4 authored Jun 11, 2015 by Janet Liu Committed by Se Wang (Patrick) Oh Jul 31, 2015

arm64: fix bug for reloading FPSIMD state after CPU hotplug.



Now FPSIMD don't handle HOTPLUG_CPU. This introduces bug after cpu down/up process.

After cpu down/up process, the FPSMID hardware register is default value, not any
process's fpsimd context. when CPU_DEAD set cpu's fpsimd_state to NULL, it will force
to load the fpsimd context for the thread, to avoid the chance to skip to load the context.
If process A is the last user process on CPU N before cpu down, and the first user process
on the same CPU N after cpu up, A's fpsimd_state.cpu is the current cpu id,
and per_cpu(fpsimd_last_state) points A's fpsimd_state, so kernel will not reload the
context during it return to user space.

Change-Id: Ia16d287748b5caa7a45c4bf5102e295722e8c166
Signed-off-by: Janet Liu <janet.liu@spreadtrum.com>
Signed-off-by: Xiongshan An <xiongshan.an@spreadtrum.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
[catalin.marinas@arm.com: some mostly cosmetic clean-ups]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: 32365e64a20edcc783137ad17fdd951ab814a2fe
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Se Wang (Patrick) Oh <sewango@codeaurora.org>

parent 1aa24ca3

arch/arm64/kernel/fpsimd.c

+31 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		* along with this program. If not, see <http://www.gnu.org/licenses/>.
		*/

		#include <linux/cpu.h>
		#include <linux/cpu_pm.h>
		#include <linux/kernel.h>
		#include <linux/init.h>
		@@ -296,6 +297,35 @@ static void fpsimd_pm_init(void)
		static inline void fpsimd_pm_init(void) { }
		#endif /* CONFIG_CPU_PM */

		#ifdef CONFIG_HOTPLUG_CPU
		static int fpsimd_cpu_hotplug_notifier(struct notifier_block *nfb,
		unsigned long action,
		void *hcpu)
		{
		unsigned int cpu = (long)hcpu;

		switch (action) {
		case CPU_DEAD:
		case CPU_DEAD_FROZEN:
		per_cpu(fpsimd_last_state, cpu) = NULL;
		break;
		}
		return NOTIFY_OK;
		}

		static struct notifier_block fpsimd_cpu_hotplug_notifier_block = {
		.notifier_call = fpsimd_cpu_hotplug_notifier,
		};

		static inline void fpsimd_hotplug_init(void)
		{
		register_cpu_notifier(&fpsimd_cpu_hotplug_notifier_block);
		}

		#else
		static inline void fpsimd_hotplug_init(void) { }
		#endif

		/*
		* FP/SIMD support code initialisation.
		*/
		@@ -315,6 +345,7 @@ static int __init fpsimd_init(void)
		elf_hwcap \|= HWCAP_ASIMD;

		fpsimd_pm_init();
		fpsimd_hotplug_init();

		return 0;
		}