[RFC,02/11] powerpc: kvm: ensure vcpu-thread run only on primary hwthread
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Message ID 1413487800-7162-3-git-send-email-kernelfans@gmail.com
State RFC
Headers show

Commit Message

Pingfan Liu Oct. 16, 2014, 7:29 p.m. UTC
When vcpu thread runs at the first time, it will ensure to stick
to the primary thread.

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/kvm_host.h |  3 +++
 arch/powerpc/kvm/book3s_hv.c        | 17 +++++++++++++++++
 2 files changed, 20 insertions(+)

Comments

Srikar Dronamraju Nov. 12, 2014, 10:17 a.m. UTC | #1
* kernelfans@gmail.com <kernelfans@gmail.com> [2014-10-16 15:29:51]:

> When vcpu thread runs at the first time, it will ensure to stick
> to the primary thread.
> 
> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> ---
>  arch/powerpc/include/asm/kvm_host.h |  3 +++
>  arch/powerpc/kvm/book3s_hv.c        | 17 +++++++++++++++++
>  2 files changed, 20 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 98d9dd5..9a3355e 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -666,6 +666,9 @@ struct kvm_vcpu_arch {
>  	spinlock_t tbacct_lock;
>  	u64 busy_stolen;
>  	u64 busy_preempt;
> +#ifdef CONFIG_KVMPPC_ENABLE_SECONDARY
> +	bool cpu_selected;
> +#endif
>  #endif
>  };
>  
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 27cced9..ba258c8 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -1909,6 +1909,23 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
>  {
>  	int r;
>  	int srcu_idx;
> +#ifdef CONFIG_KVMPPC_ENABLE_SECONDARY
> +	int cpu = smp_processor_id();
> +	int target_cpu;
> +	unsigned int cpu;

2 variables with same name... cpu

> +	struct task_struct *p = current;
> +
> +	if (unlikely(!vcpu->arch.cpu_selected)) {
> +		vcpu->arch.cpu_selected = true;

Nit: something like cpumask_set seems to be better than cpu_selected

> +		for (cpu = 0; cpu < NR_CPUS; cpu+=threads_per_core) {
> +			cpumask_set_cpu(cpu, &p->sys_allowed);
		Dont we need to reset the cpumask first before we set
		the cpumask here?

> +		}
> +		if (cpu%threads_per_core != 0) {

At this time, cpu should be NR_CPUS and most times it should be a
multiple of threads_per_core. Unfortunately there wont be a cpu with
cpu number NR_CPUS.

> +			target_cpu = cpu/threads_per_core*threads_per_core;

Its probably better of to have parenthesis here. 

> +			migrate_task_to(current, target_cpu);
We are probably migrating to a non-existant cpu.
Also dont you need to check if the target_cpu is part of the cpumask?

> +		}
> +	}
> +#endif
>  
>  	if (!vcpu->arch.sane) {
>  		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> -- 
> 1.8.3.1
> 
>

Patch
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diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 98d9dd5..9a3355e 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -666,6 +666,9 @@  struct kvm_vcpu_arch {
 	spinlock_t tbacct_lock;
 	u64 busy_stolen;
 	u64 busy_preempt;
+#ifdef CONFIG_KVMPPC_ENABLE_SECONDARY
+	bool cpu_selected;
+#endif
 #endif
 };
 
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 27cced9..ba258c8 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1909,6 +1909,23 @@  static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
 {
 	int r;
 	int srcu_idx;
+#ifdef CONFIG_KVMPPC_ENABLE_SECONDARY
+	int cpu = smp_processor_id();
+	int target_cpu;
+	unsigned int cpu;
+	struct task_struct *p = current;
+
+	if (unlikely(!vcpu->arch.cpu_selected)) {
+		vcpu->arch.cpu_selected = true;
+		for (cpu = 0; cpu < NR_CPUS; cpu+=threads_per_core) {
+			cpumask_set_cpu(cpu, &p->sys_allowed);
+		}
+		if (cpu%threads_per_core != 0) {
+			target_cpu = cpu/threads_per_core*threads_per_core;
+			migrate_task_to(current, target_cpu);
+		}
+	}
+#endif
 
 	if (!vcpu->arch.sane) {
 		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;