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@xxxxxxxxxx> wrote:
> >
> > On Sun, Sep 10, 2023 at 04:29:06AM -0400, guoren@xxxxxxxxxx wrote:
> > > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> > > ---
> > > 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@xxxxxxxxxx>
> >
> > 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
>
