Commit 32365e64 authored by Janet Liu's avatar Janet Liu Committed by Catalin Marinas

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.
Signed-off-by: default avatarJanet Liu <>
Signed-off-by: default avatarXiongshan An <>
Signed-off-by: default avatarChunyan Zhang <>
[ some mostly cosmetic clean-ups]
Signed-off-by: default avatarCatalin Marinas <>
parent 6eb6c801
......@@ -17,6 +17,7 @@
* along with this program. If not, see <>.
#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 */
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:
per_cpu(fpsimd_last_state, cpu) = NULL;
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)
static inline void fpsimd_hotplug_init(void) { }
* FP/SIMD support code initialisation.
......@@ -315,6 +345,7 @@ static int __init fpsimd_init(void)
elf_hwcap |= HWCAP_ASIMD;
return 0;
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