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| Started by | Juergen Gross <jgross@suse.com> |
|---|---|
| First post | 2017-09-06 17:30 +0200 |
| Last post | 2017-09-06 20:00 +0200 |
| Articles | 5 — 3 participants |
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[PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() Juergen Gross <jgross@suse.com> - 2017-09-06 17:30 +0200
Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() Waiman Long <longman@redhat.com> - 2017-09-06 17:50 +0200
Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() Peter Zijlstra <peterz@infradead.org> - 2017-09-06 18:10 +0200
Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() Waiman Long <longman@redhat.com> - 2017-09-06 18:20 +0200
Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() Juergen Gross <jgross@suse.com> - 2017-09-06 20:00 +0200
| From | Juergen Gross <jgross@suse.com> |
|---|---|
| Date | 2017-09-06 17:30 +0200 |
| Subject | [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() |
| Message-ID | <umKr7-3Dj-9@gated-at.bofh.it> |
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>
---
arch/x86/include/asm/qspinlock.h | 11 +++++++++++
arch/x86/kernel/paravirt-spinlocks.c | 6 ++++++
arch/x86/kernel/smpboot.c | 2 ++
kernel/locking/qspinlock.c | 4 ++++
4 files changed, 23 insertions(+)
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index 48a706f641f2..fc39389f196b 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>
@@ -46,9 +47,15 @@ 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_branch_likely(&virt_spin_lock_key))
+ return false;
if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
return false;
@@ -65,6 +72,10 @@ 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-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
index 8f2d1c9d43a8..2fc65ddea40d 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/misc.h>
+#include <asm/qspinlock.h>
/* Number of siblings per CPU package */
int smp_num_siblings = 1;
@@ -1381,6 +1382,7 @@ 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)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 294294c71ba4..838d235b87ef 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -76,6 +76,10 @@
#define MAX_NODES 4
#endif
+#ifdef CONFIG_PARAVIRT
+DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
+#endif
+
/*
* Per-CPU queue node structures; we can never have more than 4 nested
* contexts: task, softirq, hardirq, nmi.
--
2.12.3
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| From | Waiman Long <longman@redhat.com> |
|---|---|
| Date | 2017-09-06 17:50 +0200 |
| Subject | Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() |
| Message-ID | <umKKt-3MF-9@gated-at.bofh.it> |
| In reply to | #1727603 |
On 09/06/2017 11:29 AM, Juergen Gross wrote:
> 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>
> ---
> arch/x86/include/asm/qspinlock.h | 11 +++++++++++
> arch/x86/kernel/paravirt-spinlocks.c | 6 ++++++
> arch/x86/kernel/smpboot.c | 2 ++
> kernel/locking/qspinlock.c | 4 ++++
> 4 files changed, 23 insertions(+)
>
> diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
> index 48a706f641f2..fc39389f196b 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>
> @@ -46,9 +47,15 @@ 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_branch_likely(&virt_spin_lock_key))
> + return false;
> if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
> return false;
>
> @@ -65,6 +72,10 @@ 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-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
> index 8f2d1c9d43a8..2fc65ddea40d 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/misc.h>
> +#include <asm/qspinlock.h>
>
> /* Number of siblings per CPU package */
> int smp_num_siblings = 1;
> @@ -1381,6 +1382,7 @@ 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)
> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
> index 294294c71ba4..838d235b87ef 100644
> --- a/kernel/locking/qspinlock.c
> +++ b/kernel/locking/qspinlock.c
> @@ -76,6 +76,10 @@
> #define MAX_NODES 4
> #endif
>
> +#ifdef CONFIG_PARAVIRT
> +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
> +#endif
> +
> /*
> * Per-CPU queue node structures; we can never have more than 4 nested
> * contexts: task, softirq, hardirq, nmi.
Acked-by: Waiman Long <longman@redhat.com>
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| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2017-09-06 18:10 +0200 |
| Subject | Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() |
| Message-ID | <umL3P-49l-5@gated-at.bofh.it> |
| In reply to | #1727616 |
On Wed, Sep 06, 2017 at 11:49:49AM -0400, Waiman Long wrote:
> > #define virt_spin_lock virt_spin_lock
> > static inline bool virt_spin_lock(struct qspinlock *lock)
> > {
> > + if (!static_branch_likely(&virt_spin_lock_key))
> > + return false;
> > if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
> > return false;
> >
Now native has two NOPs instead of one. Can't we merge these two static
branches?
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| From | Waiman Long <longman@redhat.com> |
|---|---|
| Date | 2017-09-06 18:20 +0200 |
| Subject | Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() |
| Message-ID | <umLdw-4da-7@gated-at.bofh.it> |
| In reply to | #1727625 |
On 09/06/2017 12:04 PM, Peter Zijlstra wrote:
> On Wed, Sep 06, 2017 at 11:49:49AM -0400, Waiman Long wrote:
>>> #define virt_spin_lock virt_spin_lock
>>> static inline bool virt_spin_lock(struct qspinlock *lock)
>>> {
>>> + if (!static_branch_likely(&virt_spin_lock_key))
>>> + return false;
>>> if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
>>> return false;
>>>
> Now native has two NOPs instead of one. Can't we merge these two static
> branches?
I guess we can remove the static_cpu_has() call. Just that any spin_lock
calls before native_pv_lock_init() will use the virt_spin_lock(). That
is still OK as the init call is done before SMP starts.
Cheers,
Longman
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| From | Juergen Gross <jgross@suse.com> |
|---|---|
| Date | 2017-09-06 20:00 +0200 |
| Subject | Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock() |
| Message-ID | <umMMi-57w-13@gated-at.bofh.it> |
| In reply to | #1727633 |
On 06/09/17 18:13, Waiman Long wrote:
> On 09/06/2017 12:04 PM, Peter Zijlstra wrote:
>> On Wed, Sep 06, 2017 at 11:49:49AM -0400, Waiman Long wrote:
>>>> #define virt_spin_lock virt_spin_lock
>>>> static inline bool virt_spin_lock(struct qspinlock *lock)
>>>> {
>>>> + if (!static_branch_likely(&virt_spin_lock_key))
>>>> + return false;
>>>> if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
>>>> return false;
>>>>
>> Now native has two NOPs instead of one. Can't we merge these two static
>> branches?
>
>
> I guess we can remove the static_cpu_has() call. Just that any spin_lock
> calls before native_pv_lock_init() will use the virt_spin_lock(). That
> is still OK as the init call is done before SMP starts.
Hmm, right. I'll send V3 in some minutes.
Juergen
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