arm64: fix bug for reloading FPSIMD state after CPU hotplug. (32365e64) · Commits · 戴 / test

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. 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>

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;
		}

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