diff options
| author | Juergen Gross <jgross@suse.com> | 2017-09-06 19:36:24 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-10-10 11:50:12 +0200 |
| commit | 9043442b43b1fddf202591b84702863286700c1a (patch) | |
| tree | 705f0e7893ff4f54d07fdd0374e46f5fa0773c1a /arch | |
| parent | af1a34f21150af199f066dfcccbae9830c9429aa (diff) | |
locking/paravirt: Use new static key for controlling call of virt_spin_lock()
There are cases where a guest tries to switch spinlocks to bare metal
behavior (e.g. by setting "xen_nopvspin" boot parameter). Today this
has the downside of falling back to unfair test and set scheme for
qspinlocks due to virt_spin_lock() detecting the virtualized
environment.
Add a static key controlling whether virt_spin_lock() should be
called or not. When running on bare metal set the new key to false.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akataria@vmware.com
Cc: boris.ostrovsky@oracle.com
Cc: chrisw@sous-sol.org
Cc: hpa@zytor.com
Cc: jeremy@goop.org
Cc: rusty@rustcorp.com.au
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20170906173625.18158-2-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/qspinlock.h | 11 | ||||
| -rw-r--r-- | arch/x86/kernel/paravirt.c | 14 | ||||
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 2 |
3 files changed, 24 insertions, 3 deletions
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index 48a706f641f2..308dfd0714c7 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -1,6 +1,7 @@ #ifndef _ASM_X86_QSPINLOCK_H #define _ASM_X86_QSPINLOCK_H +#include <linux/jump_label.h> #include <asm/cpufeature.h> #include <asm-generic/qspinlock_types.h> #include <asm/paravirt.h> @@ -46,10 +47,14 @@ static inline void queued_spin_unlock(struct qspinlock *lock) #endif #ifdef CONFIG_PARAVIRT +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); + +void native_pv_lock_init(void) __init; + #define virt_spin_lock virt_spin_lock static inline bool virt_spin_lock(struct qspinlock *lock) { - if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + if (!static_branch_likely(&virt_spin_lock_key)) return false; /* @@ -65,6 +70,10 @@ static inline bool virt_spin_lock(struct qspinlock *lock) return true; } +#else +static inline void native_pv_lock_init(void) +{ +} #endif /* CONFIG_PARAVIRT */ #include <asm-generic/qspinlock.h> diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index 19a3e8f961c7..041096bdef86 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -115,8 +115,18 @@ unsigned paravirt_patch_jmp(void *insnbuf, const void *target, return 5; } -/* Neat trick to map patch type back to the call within the - * corresponding structure. */ +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); + +void __init native_pv_lock_init(void) +{ + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + static_branch_disable(&virt_spin_lock_key); +} + +/* + * Neat trick to map patch type back to the call within the + * corresponding structure. + */ static void *get_call_destination(u8 type) { struct paravirt_patch_template tmpl = { diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index ad59edd84de7..361f91674ce5 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/misc.h> +#include <asm/qspinlock.h> /* Number of siblings per CPU package */ int smp_num_siblings = 1; @@ -1384,6 +1385,7 @@ void __init native_smp_prepare_boot_cpu(void) /* already set me in cpu_online_mask in boot_cpu_init() */ cpumask_set_cpu(me, cpu_callout_mask); cpu_set_state_online(me); + native_pv_lock_init(); } void __init native_smp_cpus_done(unsigned int max_cpus) |