search for: xen_pvspin

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:

...with no PV drivers. diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index d5f79ac..19e2e75 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -20,7 +20,6 @@ static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; static DEFINE_PER_CPU(char *, 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_spi...

...bel init code needs to happend _after_ the jump labels are - * enabled and before SMP is started. Hence we use pre-SMP initcall level - * init. We cannot do it in xen_init_spinlocks as that is done before - * jump labels are activated. - */ -static __init int xen_init_spinlocks_jump(void) -{ - if (!xen_pvspin) - return 0; - - if (!xen_domain()) - return 0; - - static_key_slow_inc(&paravirt_ticketlocks_enabled); - return 0; -} -early_initcall(xen_init_spinlocks_jump); - static __init int xen_parse_nopvspin(char *arg) { xen_pvspin = false; -- 1.8.3.1

...bel init code needs to happend _after_ the jump labels are - * enabled and before SMP is started. Hence we use pre-SMP initcall level - * init. We cannot do it in xen_init_spinlocks as that is done before - * jump labels are activated. - */ -static __init int xen_init_spinlocks_jump(void) -{ - if (!xen_pvspin) - return 0; - - if (!xen_domain()) - return 0; - - static_key_slow_inc(&paravirt_ticketlocks_enabled); - return 0; -} -early_initcall(xen_init_spinlocks_jump); - static __init int xen_parse_nopvspin(char *arg) { xen_pvspin = false; -- 1.8.3.1

On 11/01/2017 04:58 PM, Waiman Long wrote: > +/* TODO: To be removed in a future kernel version */ > static __init int xen_parse_nopvspin(char *arg) > { > - xen_pvspin = false; > + pr_warn("xen_nopvspin is deprecated, replace it with \"pvlock_type=queued\"!\n"); > + if (!pv_spinlock_type) > + pv_spinlock_type = locktype_queued; Since we currently end up using unfair locks and because you are deprecating xen_nopvspin I wonder whether...

On 11/01/2017 04:58 PM, Waiman Long wrote: > +/* TODO: To be removed in a future kernel version */ > static __init int xen_parse_nopvspin(char *arg) > { > - xen_pvspin = false; > + pr_warn("xen_nopvspin is deprecated, replace it with \"pvlock_type=queued\"!\n"); > + if (!pv_spinlock_type) > + pv_spinlock_type = locktype_queued; Since we currently end up using unfair locks and because you are deprecating xen_nopvspin I wonder whether...

...er_ the jump labels are > - * enabled and before SMP is started. Hence we use pre-SMP initcall level > - * init. We cannot do it in xen_init_spinlocks as that is done before > - * jump labels are activated. > - */ > -static __init int xen_init_spinlocks_jump(void) > -{ > - if (!xen_pvspin) > - return 0; > - > - if (!xen_domain()) > - return 0; > - > - static_key_slow_inc(&paravirt_ticketlocks_enabled); > - return 0; > -} > -early_initcall(xen_init_spinlocks_jump); > - > static __init int xen_parse_nopvspin(char *arg) > { > xen_pvspin...

...74c..b019b2a 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -95,17 +95,43 @@ static inline void spin_time_accum_blocked(u64 start) } #endif /* CONFIG_XEN_DEBUG_FS */ +static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; +static DEFINE_PER_CPU(char *, irq_name); +static bool xen_pvspin = true; + +#ifdef CONFIG_QUEUE_SPINLOCK + +#include <asm/qspinlock.h> + +PV_CALLEE_SAVE_REGS_THUNK(__pv_queue_spin_unlock); + +static void xen_qlock_wait(u8 *ptr, u8 val) +{ + int irq = __this_cpu_read(lock_kicker_irq); + + xen_clear_irq_pending(irq); + + barrier(); + + if (READ_ONCE(*ptr) ==...

...74c..b019b2a 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -95,17 +95,43 @@ static inline void spin_time_accum_blocked(u64 start) } #endif /* CONFIG_XEN_DEBUG_FS */ +static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; +static DEFINE_PER_CPU(char *, irq_name); +static bool xen_pvspin = true; + +#ifdef CONFIG_QUEUE_SPINLOCK + +#include <asm/qspinlock.h> + +PV_CALLEE_SAVE_REGS_THUNK(__pv_queue_spin_unlock); + +static void xen_qlock_wait(u8 *ptr, u8 val) +{ + int irq = __this_cpu_read(lock_kicker_irq); + + xen_clear_irq_pending(irq); + + barrier(); + + if (READ_ONCE(*ptr) ==...

...x86/xen/spinlock.c index 956374c..728b45b 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -17,6 +17,55 @@ #include "xen-ops.h" #include "debugfs.h" +static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; +static DEFINE_PER_CPU(char *, irq_name); +static bool xen_pvspin = true; + +#ifdef CONFIG_QUEUE_SPINLOCK + +#include <asm/qspinlock.h> + +static void xen_qlock_kick(int cpu) +{ + xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR); +} + +/* + * Halt the current CPU & release it back to the host + */ +static void xen_qlock_wait(u8 *byte, u8 val) +{ + int irq...

...x86/xen/spinlock.c index 06f4a64..6bbe798 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -17,6 +17,12 @@ #include "xen-ops.h" #include "debugfs.h" +static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; +static DEFINE_PER_CPU(char *, irq_name); +static bool xen_pvspin = true; + +#ifndef CONFIG_QUEUE_SPINLOCK + enum xen_contention_stat { TAKEN_SLOW, TAKEN_SLOW_PICKUP, @@ -100,12 +106,9 @@ struct xen_lock_waiting { __ticket_t want; }; -static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; -static DEFINE_PER_CPU(char *, irq_name); static DEFINE_PER_CPU(struc...

...x86/xen/spinlock.c index d332ae0..60e444c 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -17,6 +17,12 @@ #include "xen-ops.h" #include "debugfs.h" +static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; +static DEFINE_PER_CPU(char *, irq_name); +static bool xen_pvspin = true; + +#ifndef CONFIG_QUEUE_SPINLOCK + enum xen_contention_stat { TAKEN_SLOW, TAKEN_SLOW_PICKUP, @@ -100,12 +106,9 @@ struct xen_lock_waiting { __ticket_t want; }; -static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; -static DEFINE_PER_CPU(char *, irq_name); static DEFINE_PER_CPU(struc...

...x86/xen/spinlock.c index d332ae0..60e444c 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -17,6 +17,12 @@ #include "xen-ops.h" #include "debugfs.h" +static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; +static DEFINE_PER_CPU(char *, irq_name); +static bool xen_pvspin = true; + +#ifndef CONFIG_QUEUE_SPINLOCK + enum xen_contention_stat { TAKEN_SLOW, TAKEN_SLOW_PICKUP, @@ -100,12 +106,9 @@ struct xen_lock_waiting { __ticket_t want; }; -static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; -static DEFINE_PER_CPU(char *, irq_name); static DEFINE_PER_CPU(struc...

...o); 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 1e1462d..9fc8eab 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -82,7 +82,7 @@ void xen_init_lock_cpu(int cpu) char *name; if (!xen_pvspin) { - if (cpu == 0) + if ((cpu == 0) && (pv_spinlock_type == locktype_auto)) static_branch_disable(&virt_spin_lock_key); return; } @@ -130,8 +130,8 @@ void xen_uninit_lock_cpu(int cpu) */ void __init xen_init_spinlocks(void) { - - if (!xen_pvspin) { + if (!xen_pvspin || (p...

...o); 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 1e1462d..9fc8eab 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -82,7 +82,7 @@ void xen_init_lock_cpu(int cpu) char *name; if (!xen_pvspin) { - if (cpu == 0) + if ((cpu == 0) && (pv_spinlock_type == locktype_auto)) static_branch_disable(&virt_spin_lock_key); return; } @@ -130,8 +130,8 @@ void xen_uninit_lock_cpu(int cpu) */ void __init xen_init_spinlocks(void) { - - if (!xen_pvspin) { + if (!xen_pvspin || (p...

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

...xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -10,6 +10,7 @@ #include <linux/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

On 11/01/2017 06:01 PM, Boris Ostrovsky wrote: > On 11/01/2017 04:58 PM, Waiman Long wrote: >> +/* TODO: To be removed in a future kernel version */ >> static __init int xen_parse_nopvspin(char *arg) >> { >> - xen_pvspin = false; >> + pr_warn("xen_nopvspin is deprecated, replace it with \"pvlock_type=queued\"!\n"); >> + if (!pv_spinlock_type) >> + pv_spinlock_type = locktype_queued; > Since we currently end up using unfair locks and because you are > deprecating xen_nopv...