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SubjectRe: [PATCH v3] KVM: Check the allocation of pv cpu mask
Date
lihaiwei.kernel@gmail.com writes:

> From: Haiwei Li <lihaiwei@tencent.com>
>
> check the allocation of per-cpu __pv_cpu_mask.
>
> Suggested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: Haiwei Li <lihaiwei@tencent.com>
> ---
> v1 -> v2:
> * add CONFIG_SMP for kvm_send_ipi_mask_allbutself to prevent build error
> v2 -> v3:
> * always check the allocation of __pv_cpu_mask in kvm_flush_tlb_others
>
> arch/x86/kernel/kvm.c | 27 ++++++++++++++++++++++++---
> 1 file changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 9663ba31347c..1e5da6db519c 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -553,7 +553,6 @@ static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
> static void kvm_setup_pv_ipi(void)
> {
> apic->send_IPI_mask = kvm_send_ipi_mask;
> - apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;

I see that kvm_send_ipi_mask_allbutself() uses per CPU __pv_cpu_mask and
kvm_send_ipi_mask doesn't but assigning send_IPI_mask here and
send_IPI_mask_allbutself in kvm_alloc_cpumask() looks weird. Personally,
I'd prefet to move apic->send_IPI_mask to kvm_alloc_cpumask() too
(probably call kvm_setup_pv_ipi() and get rid of kvm_apic_init()
completely).

Alternatively, we can save the original apic->send_IPI_mask_allbutself
value to a variable and call it from kvm_send_ipi_mask_allbutself() when
__pv_cpu_mask wasn't allocated.

> pr_info("setup PV IPIs\n");
> }
>
> @@ -619,6 +618,11 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
> struct kvm_steal_time *src;
> struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
>
> + if (unlikely(!flushmask)) {
> + native_flush_tlb_others(cpumask, info);
> + return;
> + }
> +
> cpumask_copy(flushmask, cpumask);
> /*
> * We have to call flush only on online vCPUs. And
> @@ -765,6 +769,14 @@ static __init int activate_jump_labels(void)
> }
> arch_initcall(activate_jump_labels);
>
> +static void kvm_free_cpumask(void)
> +{
> + unsigned int cpu;
> +
> + for_each_possible_cpu(cpu)
> + free_cpumask_var(per_cpu(__pv_cpu_mask, cpu));
> +}
> +
> static __init int kvm_alloc_cpumask(void)
> {
> int cpu;
> @@ -783,11 +795,20 @@ static __init int kvm_alloc_cpumask(void)
>
> if (alloc)
> for_each_possible_cpu(cpu) {
> - zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
> - GFP_KERNEL, cpu_to_node(cpu));
> + if (!zalloc_cpumask_var_node(
> + per_cpu_ptr(&__pv_cpu_mask, cpu),
> + GFP_KERNEL, cpu_to_node(cpu)))
> + goto zalloc_cpumask_fail;
> }
>
> +#if defined(CONFIG_SMP)
> + apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
> +#endif
> return 0;
> +
> +zalloc_cpumask_fail:
> + kvm_free_cpumask();
> + return -ENOMEM;
> }
> arch_initcall(kvm_alloc_cpumask);

--
Vitaly

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