Linux Virtualization - Mar 2014 - [PATCH v7 06/11] pvqspinlock, x86: Allow unfair queue spinlock in a KVM guest

Il 19/03/2014 21:14, Waiman Long ha scritto:
> This patch adds a KVM init function to activate the unfair queue
> spinlock in a KVM guest when the PARAVIRT_UNFAIR_LOCKS kernel config
> option is selected.
>
> Signed-off-by: Waiman Long <Waiman.Long at hp.com>
> ---
>  arch/x86/kernel/kvm.c |   17 +++++++++++++++++
>  1 files changed, 17 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 713f1b3..a489140 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -826,3 +826,20 @@ static __init int kvm_spinlock_init_jump(void)
>  early_initcall(kvm_spinlock_init_jump);
>
>  #endif	/* CONFIG_PARAVIRT_SPINLOCKS */
> +
> +#ifdef CONFIG_PARAVIRT_UNFAIR_LOCKS
> +/*
> + * Enable unfair lock if running in a real para-virtualized environment
> + */
> +static __init int kvm_unfair_locks_init_jump(void)
> +{
> +	if (!kvm_para_available())
> +		return 0;
> +
> +	static_key_slow_inc(&paravirt_unfairlocks_enabled);
> +	printk(KERN_INFO "KVM setup unfair spinlock\n");
> +
> +	return 0;
> +}
> +early_initcall(kvm_unfair_locks_init_jump);
> +#endif
>
No!  Please do what I asked you to do.  You are not handling Hyper-V or 
VMWare.  Just use X86_FEATURE_HYPERVISOR and it will cover all 
hypervisors that actually follow Intel's guidelines.

Paolo

On 03/20/2014 03:01 PM, Paolo Bonzini wrote:
> 
> No!  Please do what I asked you to do.  You are not handling Hyper-V or
> VMWare.  Just use X86_FEATURE_HYPERVISOR and it will cover all
> hypervisors that actually follow Intel's guidelines.
> 
And for those that don't, we should turn on X86_FEATURE_HYPERVISOR in
the Linux enumeration code as we do for other features we detect
independently.

	-hpa

Il 20/03/2014 23:29, H. Peter Anvin ha scritto:
> > No!  Please do what I asked you to do.  You are not handling Hyper-V
or
> > VMWare.  Just use X86_FEATURE_HYPERVISOR and it will cover all
> > hypervisors that actually follow Intel's guidelines.
>
> And for those that don't, we should turn on X86_FEATURE_HYPERVISOR in
> the Linux enumeration code as we do for other features we detect
> independently.
Yeah, but all the hypervisors we detect right now are fine.  Not 
surprising, since Microsoft won't certify Windows on your hypervisor 
unless you set the bit, and KVM/Xen/VMware are all certified (Hyper-V 
does not go through the same certification, but sets it anyway).

I got a second-hand report that VirtualBox doesn't set it---and I 
haven't verified that yet---but we don't even try to detect vbox right
now.

Paolo

On 03/20/2014 06:01 PM, Paolo Bonzini wrote:
> Il 19/03/2014 21:14, Waiman Long ha scritto:
>> This patch adds a KVM init function to activate the unfair queue
>> spinlock in a KVM guest when the PARAVIRT_UNFAIR_LOCKS kernel config
>> option is selected.
>>
>> Signed-off-by: Waiman Long <Waiman.Long at hp.com>
>> ---
>>  arch/x86/kernel/kvm.c |   17 +++++++++++++++++
>>  1 files changed, 17 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index 713f1b3..a489140 100644
>> --- a/arch/x86/kernel/kvm.c
>> +++ b/arch/x86/kernel/kvm.c
>> @@ -826,3 +826,20 @@ static __init int kvm_spinlock_init_jump(void)
>>  early_initcall(kvm_spinlock_init_jump);
>>
>>  #endif    /* CONFIG_PARAVIRT_SPINLOCKS */
>> +
>> +#ifdef CONFIG_PARAVIRT_UNFAIR_LOCKS
>> +/*
>> + * Enable unfair lock if running in a real para-virtualized
environment
>> + */
>> +static __init int kvm_unfair_locks_init_jump(void)
>> +{
>> +    if (!kvm_para_available())
>> +        return 0;
>> +
>> +    static_key_slow_inc(&paravirt_unfairlocks_enabled);
>> +    printk(KERN_INFO "KVM setup unfair spinlock\n");
>> +
>> +    return 0;
>> +}
>> +early_initcall(kvm_unfair_locks_init_jump);
>> +#endif
>>
>
> No!  Please do what I asked you to do.  You are not handling Hyper-V 
> or VMWare.  Just use X86_FEATURE_HYPERVISOR and it will cover all 
> hypervisors that actually follow Intel's guidelines.
>
> Paolo
OK, I can modify the patch to use X86_FEATURE_HYPERVISOR.

-Longman