linux-kernel - [PATCH v2 2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu

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Message-Id: <20190412171420.29065-3-julien.grall@arm.com>
Date:   Fri, 12 Apr 2019 18:14:19 +0100
From:   Julien Grall <julien.grall@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will.deacon@....com,
        christoffer.dall@....com, marc.zyngier@....com,
        james.morse@....com, julien.thierry@....com,
        suzuki.poulose@....com, Dave.Martin@....com,
        ard.biesheuvel@...aro.org, Julien Grall <julien.grall@....com>
Subject: [PATCH v2 2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu_state() and use it

The only external user of fpsimd_save() and fpsimd_flush_cpu_state() is
the KVM FPSIMD code.

A follow-up patch will mandate hold of the FPSIMD context while
modifying it. 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@....com>

---
    Changes in v2:
        - Patch added
---
 arch/arm64/include/asm/fpsimd.h |  5 ++---
 arch/arm64/kernel/fpsimd.c      | 17 +++++++++++++----
 arch/arm64/kvm/fpsimd.c         |  3 +--
 3 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 32abbfd852e8..88c223f6ded6 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -48,11 +48,11 @@ 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);
 
+extern void fpsimd_save_and_flush_cpu_state(void);
+
 extern void fpsimd_signal_preserve_current_state(void);
 extern void fpsimd_preserve_current_state(void);
 extern void fpsimd_restore_current_state(void);
@@ -63,7 +63,6 @@ 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);
 
 /* 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 577296bba730..9e4e4b6acd93 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -241,7 +241,7 @@ 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);
@@ -1117,12 +1117,22 @@ 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);
@@ -1279,8 +1289,7 @@ 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..01bd2e862506 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -113,8 +113,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 		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