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SubjectRe: [PATCH v2] KVM: Check the allocation of pv cpu mask
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On 20/9/3 18:39, Vitaly Kuznetsov wrote:
> Haiwei Li <lihaiwei.kernel@gmail.com> writes:
>
>> From: Haiwei Li <lihaiwei@tencent.com>
>>
>> check the allocation of per-cpu __pv_cpu_mask. Initialize ops only when
>> successful.
>>
>> Signed-off-by: Haiwei Li <lihaiwei@tencent.com>
>> ---
>> arch/x86/kernel/kvm.c | 24 ++++++++++++++++++++----
>> 1 file changed, 20 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index 08320b0b2b27..d3c062e551d7 100644
>> --- a/arch/x86/kernel/kvm.c
>> +++ b/arch/x86/kernel/kvm.c
>> @@ -555,7 +555,6 @@ 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;
>> pr_info("setup PV IPIs\n");
>> }
>>
>> @@ -654,7 +653,6 @@ static void __init kvm_guest_init(void)
>> }
>>
>> if (pv_tlb_flush_supported()) {
>> - pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
>> pv_ops.mmu.tlb_remove_table = tlb_remove_table;
>> pr_info("KVM setup pv remote TLB flush\n");
>> }
>> @@ -767,6 +765,14 @@ static __init int activate_jump_labels(void)
>> }
>> arch_initcall(activate_jump_labels);
>>
>> +static void kvm_free_pv_cpu_mask(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;
>> @@ -785,11 +791,21 @@ 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
>> + pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
>
> This is too late I'm afraid. If I'm not mistaken PV patching happens
> earlier, so .init.guest_late_init (kvm_guest_init()) is good and
> arch_initcall() is bad.

.init.guest_late_init (kvm_guest_init()) is called before
arch_initcall() and kvm_flush_tlb_others && kvm_send_ipi_mask_allbutself
rely on __pv_cpu_mask. So, i can not put this assign in kvm_guest_init().

>
> Have you checked that with this patch kvm_flush_tlb_others() is still
> being called?

yes. I add a printk and i get the log.

>
> Actually, there is no need to assign kvm_flush_tlb_others() so late. We
> can always check if __pv_cpu_mask was allocated and revert back to the
> architectural path if not.
I am sorry i don't really understand. Can you explain in more detail? Thx.

>
>> return 0;
>> +
>> +zalloc_cpumask_fail:
>> + kvm_free_pv_cpu_mask();
>> + return -ENOMEM;
>> }
>> arch_initcall(kvm_alloc_cpumask);
>>
>> --
>> 2.18.4
>>
>

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