diff mbox series

[V11,12/17] RISC-V: paravirt: pvqspinlock: Add nopvspin kernel parameter

Message ID 20230910082911.3378782-13-guoren@kernel.org (mailing list archive)
State New, archived
Headers show
Series riscv: Add Native/Paravirt qspinlock support | expand

Commit Message

Guo Ren Sept. 10, 2023, 8:29 a.m. UTC 
From: Guo Ren <guoren@linux.alibaba.com>

Disables the qspinlock slow path using PV optimizations which
allow the hypervisor to 'idle' the guest on lock contention.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  2 +-
 arch/riscv/kernel/qspinlock_paravirt.c          | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

Comments

Leonardo Bras Sept. 15, 2023, 6:05 a.m. UTC | #1 
On Sun, Sep 10, 2023 at 04:29:06AM -0400, guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> Disables the qspinlock slow path using PV optimizations which
> allow the hypervisor to 'idle' the guest on lock contention.
> 
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  2 +-
>  arch/riscv/kernel/qspinlock_paravirt.c          | 13 +++++++++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index f75bedc50e00..e74aed631573 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3857,7 +3857,7 @@
>  			as generic guest with no PV drivers. Currently support
>  			XEN HVM, KVM, HYPER_V and VMWARE guest.
>  
> -	nopvspin	[X86,XEN,KVM]
> +	nopvspin	[X86,XEN,KVM,RISC-V]
>  			Disables the qspinlock slow path using PV optimizations
>  			which allow the hypervisor to 'idle' the guest on lock
>  			contention.
> diff --git a/arch/riscv/kernel/qspinlock_paravirt.c b/arch/riscv/kernel/qspinlock_paravirt.c
> index 85ff5a3ec234..a0ad4657f437 100644
> --- a/arch/riscv/kernel/qspinlock_paravirt.c
> +++ b/arch/riscv/kernel/qspinlock_paravirt.c
> @@ -41,8 +41,21 @@ EXPORT_STATIC_CALL(pv_queued_spin_lock_slowpath);
>  DEFINE_STATIC_CALL(pv_queued_spin_unlock, native_queued_spin_unlock);
>  EXPORT_STATIC_CALL(pv_queued_spin_unlock);
>  
> +static bool nopvspin;

It is only used in init, so it makes sense to add __initdata.

static bool nopvspin __initdata;

Other than that, LGTM:
Reviewed-by: Leonardo Bras <leobras@redhat.com>

Thanks!
Leo

> +static __init int parse_nopvspin(char *arg)
> +{
> +       nopvspin = true;
> +       return 0;
> +}
> +early_param("nopvspin", parse_nopvspin);
> +
>  void __init pv_qspinlock_init(void)
>  {
> +	if (nopvspin) {
> +		pr_info("PV qspinlocks disabled\n");
> +		return;
> +	}
> +
>  	if (num_possible_cpus() == 1)
>  		return;
>  
> -- 
> 2.36.1
>
Guo Ren Sept. 17, 2023, 3:03 p.m. UTC | #2 
On Fri, Sep 15, 2023 at 2:05 PM Leonardo Bras <leobras@redhat.com> wrote:
>
> On Sun, Sep 10, 2023 at 04:29:06AM -0400, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > Disables the qspinlock slow path using PV optimizations which
> > allow the hypervisor to 'idle' the guest on lock contention.
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@kernel.org>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt |  2 +-
> >  arch/riscv/kernel/qspinlock_paravirt.c          | 13 +++++++++++++
> >  2 files changed, 14 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index f75bedc50e00..e74aed631573 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -3857,7 +3857,7 @@
> >                       as generic guest with no PV drivers. Currently support
> >                       XEN HVM, KVM, HYPER_V and VMWARE guest.
> >
> > -     nopvspin        [X86,XEN,KVM]
> > +     nopvspin        [X86,XEN,KVM,RISC-V]
> >                       Disables the qspinlock slow path using PV optimizations
> >                       which allow the hypervisor to 'idle' the guest on lock
> >                       contention.
> > diff --git a/arch/riscv/kernel/qspinlock_paravirt.c b/arch/riscv/kernel/qspinlock_paravirt.c
> > index 85ff5a3ec234..a0ad4657f437 100644
> > --- a/arch/riscv/kernel/qspinlock_paravirt.c
> > +++ b/arch/riscv/kernel/qspinlock_paravirt.c
> > @@ -41,8 +41,21 @@ EXPORT_STATIC_CALL(pv_queued_spin_lock_slowpath);
> >  DEFINE_STATIC_CALL(pv_queued_spin_unlock, native_queued_spin_unlock);
> >  EXPORT_STATIC_CALL(pv_queued_spin_unlock);
> >
> > +static bool nopvspin;
>
> It is only used in init, so it makes sense to add __initdata.
>
> static bool nopvspin __initdata;
Okay.

>
> Other than that, LGTM:
> Reviewed-by: Leonardo Bras <leobras@redhat.com>
>
> Thanks!
> Leo
>
> > +static __init int parse_nopvspin(char *arg)
> > +{
> > +       nopvspin = true;
> > +       return 0;
> > +}
> > +early_param("nopvspin", parse_nopvspin);
> > +
> >  void __init pv_qspinlock_init(void)
> >  {
> > +     if (nopvspin) {
> > +             pr_info("PV qspinlocks disabled\n");
> > +             return;
> > +     }
> > +
> >       if (num_possible_cpus() == 1)
> >               return;
> >
> > --
> > 2.36.1
> >
>
Leonardo Bras Sept. 19, 2023, 5:44 a.m. UTC | #3 
On Sun, Sep 17, 2023 at 11:03:30PM +0800, Guo Ren wrote:
> On Fri, Sep 15, 2023 at 2:05 PM Leonardo Bras <leobras@redhat.com> wrote:
> >
> > On Sun, Sep 10, 2023 at 04:29:06AM -0400, guoren@kernel.org wrote:
> > > From: Guo Ren <guoren@linux.alibaba.com>
> > >
> > > Disables the qspinlock slow path using PV optimizations which
> > > allow the hypervisor to 'idle' the guest on lock contention.
> > >
> > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > > Signed-off-by: Guo Ren <guoren@kernel.org>
> > > ---
> > >  Documentation/admin-guide/kernel-parameters.txt |  2 +-
> > >  arch/riscv/kernel/qspinlock_paravirt.c          | 13 +++++++++++++
> > >  2 files changed, 14 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > > index f75bedc50e00..e74aed631573 100644
> > > --- a/Documentation/admin-guide/kernel-parameters.txt
> > > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > > @@ -3857,7 +3857,7 @@
> > >                       as generic guest with no PV drivers. Currently support
> > >                       XEN HVM, KVM, HYPER_V and VMWARE guest.
> > >
> > > -     nopvspin        [X86,XEN,KVM]
> > > +     nopvspin        [X86,XEN,KVM,RISC-V]
> > >                       Disables the qspinlock slow path using PV optimizations
> > >                       which allow the hypervisor to 'idle' the guest on lock
> > >                       contention.
> > > diff --git a/arch/riscv/kernel/qspinlock_paravirt.c b/arch/riscv/kernel/qspinlock_paravirt.c
> > > index 85ff5a3ec234..a0ad4657f437 100644
> > > --- a/arch/riscv/kernel/qspinlock_paravirt.c
> > > +++ b/arch/riscv/kernel/qspinlock_paravirt.c
> > > @@ -41,8 +41,21 @@ EXPORT_STATIC_CALL(pv_queued_spin_lock_slowpath);
> > >  DEFINE_STATIC_CALL(pv_queued_spin_unlock, native_queued_spin_unlock);
> > >  EXPORT_STATIC_CALL(pv_queued_spin_unlock);
> > >
> > > +static bool nopvspin;
> >
> > It is only used in init, so it makes sense to add __initdata.
> >
> > static bool nopvspin __initdata;
> Okay.

Thx!
Leo

> 
> >
> > Other than that, LGTM:
> > Reviewed-by: Leonardo Bras <leobras@redhat.com>
> >
> > Thanks!
> > Leo
> >
> > > +static __init int parse_nopvspin(char *arg)
> > > +{
> > > +       nopvspin = true;
> > > +       return 0;
> > > +}
> > > +early_param("nopvspin", parse_nopvspin);
> > > +
> > >  void __init pv_qspinlock_init(void)
> > >  {
> > > +     if (nopvspin) {
> > > +             pr_info("PV qspinlocks disabled\n");
> > > +             return;
> > > +     }
> > > +
> > >       if (num_possible_cpus() == 1)
> > >               return;
> > >
> > > --
> > > 2.36.1
> > >
> >
> 
> 
> -- 
> Best Regards
>  Guo Ren
>
diff mbox series

Patch

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f75bedc50e00..e74aed631573 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3857,7 +3857,7 @@ 
 			as generic guest with no PV drivers. Currently support
 			XEN HVM, KVM, HYPER_V and VMWARE guest.
 
-	nopvspin	[X86,XEN,KVM]
+	nopvspin	[X86,XEN,KVM,RISC-V]
 			Disables the qspinlock slow path using PV optimizations
 			which allow the hypervisor to 'idle' the guest on lock
 			contention.
diff --git a/arch/riscv/kernel/qspinlock_paravirt.c b/arch/riscv/kernel/qspinlock_paravirt.c
index 85ff5a3ec234..a0ad4657f437 100644
--- a/arch/riscv/kernel/qspinlock_paravirt.c
+++ b/arch/riscv/kernel/qspinlock_paravirt.c
@@ -41,8 +41,21 @@  EXPORT_STATIC_CALL(pv_queued_spin_lock_slowpath);
 DEFINE_STATIC_CALL(pv_queued_spin_unlock, native_queued_spin_unlock);
 EXPORT_STATIC_CALL(pv_queued_spin_unlock);
 
+static bool nopvspin;
+static __init int parse_nopvspin(char *arg)
+{
+       nopvspin = true;
+       return 0;
+}
+early_param("nopvspin", parse_nopvspin);
+
 void __init pv_qspinlock_init(void)
 {
+	if (nopvspin) {
+		pr_info("PV qspinlocks disabled\n");
+		return;
+	}
+
 	if (num_possible_cpus() == 1)
 		return;