search for: static_branch_disable

With virt_spin_lock() being guarded by a static key the bare metal case can be optimized by patching the call away completely. In case a kernel running as a guest it can decide whether to use paravitualized spinlocks, the current fallback to the unfair test-and-set scheme, or to mimic the bare metal behavior. V2: - use static key instead of making virt_spin_lock() a pvops function Juergen Gross

With virt_spin_lock() being guarded by a static key the bare metal case can be optimized by patching the call away completely. In case a kernel running as a guest it can decide whether to use paravitualized spinlocks, the current fallback to the unfair test-and-set scheme, or to mimic the bare metal behavior. V2: - use static key instead of making virt_spin_lock() a pvops function Juergen Gross

...ock_setup); + DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); void __init native_pv_lock_init(void) { - if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + if (pv_spinlock_type == locktype_unfair) + return; + + if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || + (pv_spinlock_type != locktype_auto)) static_branch_disable(&virt_spin_lock_key); } @@ -473,3 +510,4 @@ struct pv_mmu_ops pv_mmu_ops __ro_after_init = { EXPORT_SYMBOL (pv_mmu_ops); EXPORT_SYMBOL_GPL(pv_info); EXPORT_SYMBOL (pv_irq_ops); +EXPORT_SYMBOL (pv_spinlock_type); diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index...

...ock_setup); + DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); void __init native_pv_lock_init(void) { - if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + if (pv_spinlock_type == locktype_unfair) + return; + + if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || + (pv_spinlock_type != locktype_auto)) static_branch_disable(&virt_spin_lock_key); } @@ -473,3 +510,4 @@ struct pv_mmu_ops pv_mmu_ops __ro_after_init = { EXPORT_SYMBOL (pv_mmu_ops); EXPORT_SYMBOL_GPL(pv_info); EXPORT_SYMBOL (pv_irq_ops); +EXPORT_SYMBOL (pv_spinlock_type); diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index...

v1->v2: - Make pv_spinlock_type a bit mask for easier checking. - Add patch 2 to deprecate xen_nopvspin v1 - https://lkml.org/lkml/2017/11/1/381 Patch 1 adds a new pvlock_type parameter for the administrators to specify the type of lock to be used in a para-virtualized kernel. Patch 2 deprecates Xen's xen_nopvspin parameter as it is no longer needed. Waiman Long (2): x86/paravirt:

v1->v2: - Make pv_spinlock_type a bit mask for easier checking. - Add patch 2 to deprecate xen_nopvspin v1 - https://lkml.org/lkml/2017/11/1/381 Patch 1 adds a new pvlock_type parameter for the administrators to specify the type of lock to be used in a para-virtualized kernel. Patch 2 deprecates Xen's xen_nopvspin parameter as it is no longer needed. Waiman Long (2): x86/paravirt:

...#define SECTION_SIZE (1UL << PA_SECTION_SHIFT) +#ifdef CONFIG_DEV_PAGEMAP_OPS +DEFINE_STATIC_KEY_FALSE(devmap_managed_key); +EXPORT_SYMBOL(devmap_managed_key); +static atomic_t devmap_enable; + +static void dev_pagemap_put_ops(void *data) +{ + if (atomic_dec_and_test(&devmap_enable)) + static_branch_disable(&devmap_managed_key); +} + +/* + * Toggle the static key for ->page_free() callbacks when dev_pagemap + * pages go idle. + */ +static int dev_pagemap_enable(struct device *dev) +{ + if (atomic_inc_return(&devmap_enable) == 1) + static_branch_enable(&devmap_managed_key); + + if (devm...

...#define SECTION_SIZE (1UL << PA_SECTION_SHIFT) +#ifdef CONFIG_DEV_PAGEMAP_OPS +DEFINE_STATIC_KEY_FALSE(devmap_managed_key); +EXPORT_SYMBOL(devmap_managed_key); +static atomic_t devmap_enable; + +static void dev_pagemap_put_ops(void *data) +{ + if (atomic_dec_and_test(&devmap_enable)) + static_branch_disable(&devmap_managed_key); +} + +static int dev_pagemap_get_ops(struct device *dev, struct dev_pagemap *pgmap) +{ + if (!pgmap->ops->page_free) { + WARN(1, "Missing page_free method\n"); + return -EINVAL; + } + + if (atomic_inc_return(&devmap_enable) == 1) + static_branch_enab...

...1UL << PA_SECTION_SHIFT) +#ifdef CONFIG_DEV_PAGEMAP_OPS +DEFINE_STATIC_KEY_FALSE(devmap_managed_key); +EXPORT_SYMBOL(devmap_managed_key); +static atomic_t devmap_managed_enable; + +static void devmap_managed_enable_put(void *data) +{ + if (atomic_dec_and_test(&devmap_managed_enable)) + static_branch_disable(&devmap_managed_key); +} + +static int devmap_managed_enable_get(struct device *dev, struct dev_pagemap *pgmap) +{ + if (!pgmap->ops->page_free) { + WARN(1, "Missing page_free method\n"); + return -EINVAL; + } + + if (atomic_inc_return(&devmap_managed_enable) == 1) + stat...

...CONFIG_DEV_PAGEMAP_OPS > +DEFINE_STATIC_KEY_FALSE(devmap_managed_key); > +EXPORT_SYMBOL(devmap_managed_key); > +static atomic_t devmap_managed_enable; > + > +static void devmap_managed_enable_put(void *data) > +{ > + if (atomic_dec_and_test(&devmap_managed_enable)) > + static_branch_disable(&devmap_managed_key); > +} > + > +static int devmap_managed_enable_get(struct device *dev, struct dev_pagemap *pgmap) > +{ > + if (!pgmap->ops->page_free) { NIT: later on you add the check for pgmap->ops... it should probably be here. But not sure that bisection will...

With virt_spin_lock() being guarded by a static key the bare metal case can be optimized by patching the call away completely. In case a kernel running as a guest it can decide whether to use paravitualized spinlocks, the current fallback to the unfair test-and-set scheme, or to mimic the bare metal behavior. V3: - remove test for hypervisor environment from virt_spin_lock(9 as suggested by

With virt_spin_lock() being guarded by a static key the bare metal case can be optimized by patching the call away completely. In case a kernel running as a guest it can decide whether to use paravitualized spinlocks, the current fallback to the unfair test-and-set scheme, or to mimic the bare metal behavior. V3: - remove test for hypervisor environment from virt_spin_lock(9 as suggested by

...x/slab.h> #include <asm/paravirt.h> +#include <asm/qspinlock.h> #include <xen/interface/xen.h> #include <xen/events.h> @@ -129,6 +130,7 @@ void __init xen_init_spinlocks(void) if (!xen_pvspin) { printk(KERN_DEBUG "xen: PV spinlocks disabled\n"); + static_branch_disable(&virt_spin_lock_key); return; } printk(KERN_DEBUG "xen: PV spinlocks enabled\n"); -- 2.12.3

...irq_name); -static bool xen_pvspin = true; #include <asm/qspinlock.h> @@ -81,12 +80,8 @@ void xen_init_lock_cpu(int cpu) int irq; char *name; - if (!xen_pvspin || - (pv_spinlock_type & (locktype_queued|locktype_unfair))) { - if ((cpu == 0) && !pv_spinlock_type) - static_branch_disable(&virt_spin_lock_key); + if (pv_spinlock_type & (locktype_queued|locktype_unfair)) return; - } WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n", cpu, per_cpu(lock_kicker_irq, cpu)); @@ -110,8 +105,7 @@ void xen_init_lock_cpu(int cpu)...

...5ddea40d 100644 --- a/arch/x86/kernel/paravirt-spinlocks.c +++ b/arch/x86/kernel/paravirt-spinlocks.c @@ -42,3 +42,9 @@ struct pv_lock_ops pv_lock_ops = { #endif /* SMP */ }; EXPORT_SYMBOL(pv_lock_ops); + +void __init native_pv_lock_init(void) +{ + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + static_branch_disable(&virt_spin_lock_key); +} diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 54b9e89d4d6b..21500d3ba359 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -77,6 +77,7 @@ #include <asm/i8259.h> #include <asm/realmode.h> #include <asm/...

...nlocks.c > +++ b/arch/x86/kernel/paravirt-spinlocks.c > @@ -42,3 +42,9 @@ struct pv_lock_ops pv_lock_ops = { > #endif /* SMP */ > }; > EXPORT_SYMBOL(pv_lock_ops); > + > +void __init native_pv_lock_init(void) > +{ > + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) > + static_branch_disable(&virt_spin_lock_key); > +} > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 54b9e89d4d6b..21500d3ba359 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -77,6 +77,7 @@ > #include <asm/i8259.h> > #include &...

...nlocks.c > +++ b/arch/x86/kernel/paravirt-spinlocks.c > @@ -42,3 +42,9 @@ struct pv_lock_ops pv_lock_ops = { > #endif /* SMP */ > }; > EXPORT_SYMBOL(pv_lock_ops); > + > +void __init native_pv_lock_init(void) > +{ > + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) > + static_branch_disable(&virt_spin_lock_key); > +} > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 54b9e89d4d6b..21500d3ba359 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -77,6 +77,7 @@ > #include <asm/i8259.h> > #include &...

...ck_key); > > void __init native_pv_lock_init(void) > { > - if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) > + if (pv_spinlock_type == locktype_unfair) > + return; > + > + if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || > + (pv_spinlock_type != locktype_auto)) > static_branch_disable(&virt_spin_lock_key); Really? I don't think locktype_paravirt should disable the static key. Juergen

...t native_pv_lock_init(void) >> { >> - if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) >> + if (pv_spinlock_type == locktype_unfair) >> + return; >> + >> + if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || >> + (pv_spinlock_type != locktype_auto)) >> static_branch_disable(&virt_spin_lock_key); > Really? I don't think locktype_paravirt should disable the static key. With paravirt spinlock, it doesn't matter if the static key is disabled or not. Without CONFIG_PARAVIRT_SPINLOCKS, however, it does degenerate into the native qspinlock. So you are right,...

...t native_pv_lock_init(void) >> { >> - if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) >> + if (pv_spinlock_type == locktype_unfair) >> + return; >> + >> + if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || >> + (pv_spinlock_type != locktype_auto)) >> static_branch_disable(&virt_spin_lock_key); > Really? I don't think locktype_paravirt should disable the static key. With paravirt spinlock, it doesn't matter if the static key is disabled or not. Without CONFIG_PARAVIRT_SPINLOCKS, however, it does degenerate into the native qspinlock. So you are right,...