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

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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>
This commit is contained in:
Janet Liu 2015-06-11 12:02:45 +08:00 committed by Catalin Marinas
parent 6eb6c80187
commit 32365e64a2
1 changed files with 31 additions and 0 deletions
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31
arch/arm64/kernel/fpsimd.c
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@ -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;
}