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Subject[PATCH v3 2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu_state() and use it
Date
The only external user of fpsimd_save() and fpsimd_flush_cpu_state() is
the KVM FPSIMD code.

A following patch will introduce a mechanism to acquire owernship of the
FPSIMD/SVE context for performing context management operations. Rather
than having to export the new helpers to get/put the context, we can just
introduce a new function to combine fpsimd_save() and
fpsimd_flush_cpu_state().

This has also the advantage to remove any external call of fpsimd_save()
and fpsimd_flush_cpu_state(), so they can be turned static.

Lastly, the new function can also be used in the PM notifier.

Signed-off-by: Julien Grall <julien.grall@arm.com>

---
kernel_neon_begin() does not use fpsimd_save_and_flush_cpu_state()
because the next patch will modify the function to also grab the
FPSIMD/SVE context.

Changes in v3:
- Rework the commit message
- Move the prototype of fpsimd_save_and_flush_cpu_state()
further down in the header
- Remove comment in kvm_arch_vcpu_put_fp()

Changes in v2:
- Patch added
---
arch/arm64/include/asm/fpsimd.h | 5 ++---
arch/arm64/kernel/fpsimd.c | 17 +++++++++++++----
arch/arm64/kvm/fpsimd.c | 4 +---
3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index b73d12fcc7f9..c311d36ecffe 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -48,8 +48,6 @@ struct task_struct;
extern void fpsimd_save_state(struct user_fpsimd_state *state);
extern void fpsimd_load_state(struct user_fpsimd_state *state);

-extern void fpsimd_save(void);
-
extern void fpsimd_thread_switch(struct task_struct *next);
extern void fpsimd_flush_thread(void);

@@ -63,7 +61,8 @@ extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state,
void *sve_state, unsigned int sve_vl);

extern void fpsimd_flush_task_state(struct task_struct *target);
-extern void fpsimd_flush_cpu_state(void);
+
+extern void fpsimd_save_and_flush_cpu_state(void);

/* Maximum VL that SVE VL-agnostic software can transparently support */
#define SVE_VL_ARCH_MAX 0x100
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 56afa40263d9..5313aa257be6 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -246,7 +246,7 @@ static void task_fpsimd_load(void)
*
* Softirqs (and preemption) must be disabled.
*/
-void fpsimd_save(void)
+static void fpsimd_save(void)
{
struct fpsimd_last_state_struct const *last =
this_cpu_ptr(&fpsimd_last_state);
@@ -1122,12 +1122,22 @@ void fpsimd_flush_task_state(struct task_struct *t)
* Invalidate any task's FPSIMD state that is present on this cpu.
* This function must be called with softirqs disabled.
*/
-void fpsimd_flush_cpu_state(void)
+static void fpsimd_flush_cpu_state(void)
{
__this_cpu_write(fpsimd_last_state.st, NULL);
set_thread_flag(TIF_FOREIGN_FPSTATE);
}

+/*
+ * Save the FPSIMD state to memory and invalidate cpu view.
+ * This function must be called with softirqs (and preemption) disabled.
+ */
+void fpsimd_save_and_flush_cpu_state(void)
+{
+ fpsimd_save();
+ fpsimd_flush_cpu_state();
+}
+
#ifdef CONFIG_KERNEL_MODE_NEON

DEFINE_PER_CPU(bool, kernel_neon_busy);
@@ -1284,8 +1294,7 @@ static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
{
switch (cmd) {
case CPU_PM_ENTER:
- fpsimd_save();
- fpsimd_flush_cpu_state();
+ fpsimd_save_and_flush_cpu_state();
break;
case CPU_PM_EXIT:
break;
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 6e3c9c8b2df9..525010504f9d 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -112,9 +112,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
u64 *guest_zcr = &vcpu->arch.ctxt.sys_regs[ZCR_EL1];

- /* Clean guest FP state to memory and invalidate cpu view */
- fpsimd_save();
- fpsimd_flush_cpu_state();
+ fpsimd_save_and_flush_cpu_state();

if (guest_has_sve)
*guest_zcr = read_sysreg_s(SYS_ZCR_EL12);
--
2.11.0
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