Hi Dave,
On 4/16/19 12:53 PM, Dave Martin wrote:
On Fri, Apr 12, 2019 at 06:14:19PM +0100, Julien Grall wrote:
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
This is a bit hard to read without understanding the following patch.
Maybe elaborate a bit with something like
"The following patch will introduce a mechanism to acquire ownership of the
FPSIMD/SVE context for performing context management operations. Rather than having to
export this [...]"
I will update the commit message with your suggestion.
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.gr...@arm.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);
+
Nit, bit I think this makes more sense alongside the other flush
functions.
Can you just drop this new declaration in place of the old declaration
for sve_flush_cpu_state()?
Sure, I will do it in the next version.
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();
Any reason not to do this in kernel_neon_begin() too?
In the next patch, fpsimd_save_and_flush_cpu_state() will also call
{get, put}_cpu_fpsimd_context(). So we avoid to expose the two new
functions outside of the file.
I could introduce a double-underscore version of this function if you
think it is worth it.
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 */
You can lose the comment here, since the call is now self-explanatory.
Sure.
- fpsimd_save();
- fpsimd_flush_cpu_state();
+ fpsimd_save_and_flush_cpu_state();
[...]
Otherwise, looks sensible.
Thank you for the review!
Cheers,
--
Julien Grall
