[v3,2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu_state() and use it

Message ID 20190423135719.11306-3-julien.grall@arm.com
State Superseded
Headers show
Series
  • arm64/fpsimd: Don't disable softirq when touching FPSIMD/SVE state
Related show

Commit Message

Julien Grall April 23, 2019, 1:57 p.m.
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(-)

-- 
2.11.0

Comments

Dave Martin April 24, 2019, 1:17 p.m. | #1
On Tue, Apr 23, 2019 at 02:57:18PM +0100, Julien Grall wrote:
> tent-Length: 4295

> Lines: 128

> 

> 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);


Nit: You could drop this blank line: these are all "state maintenance"
operations, roughly speaking.

But don't bother unless you respin for some other reason.

[...]

With or without that,

Reviewed-by: Dave Martin <Dave.Martin@arm.com>


Cheers
---Dave
Julien Grall April 25, 2019, 12:37 p.m. | #2
Hi Dave,

On 24/04/2019 14:17, Dave Martin wrote:
> On Tue, Apr 23, 2019 at 02:57:18PM +0100, Julien Grall wrote:

>> tent-Length: 4295

>> Lines: 128

>>

>> 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);

> 

> Nit: You could drop this blank line: these are all "state maintenance"

> operations, roughly speaking.

> 

> But don't bother unless you respin for some other reason.


It looks like I will need to make some changes in patch #3. So I will remove the 
line at the same time.

> 

> [...]

> 

> With or without that,

> 

> Reviewed-by: Dave Martin <Dave.Martin@arm.com>


Thank you!

Cheers,

-- 
Julien Grall
Dave Martin April 25, 2019, 2:12 p.m. | #3
On Thu, Apr 25, 2019 at 01:37:40PM +0100, Julien Grall wrote:
> Hi Dave,

> 

> On 24/04/2019 14:17, Dave Martin wrote:

> >On Tue, Apr 23, 2019 at 02:57:18PM +0100, Julien Grall wrote:

> >>tent-Length: 4295

> >>Lines: 128

> >>

> >>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);

> >

> >Nit: You could drop this blank line: these are all "state maintenance"

> >operations, roughly speaking.

> >

> >But don't bother unless you respin for some other reason.

> 

> It looks like I will need to make some changes in patch #3. So I will remove

> the line at the same time.


OK, fair enough.

Cheers
---Dave

Patch

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);