linux-kernel - Re: [PATCH v5 8/8] KVM: Make kvm_make_vcpus_request_mask() use pre-allocated cpu_kick

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Message-ID: <87wnnu416f.fsf@vitty.brq.redhat.com>
Date:   Mon, 06 Sep 2021 09:23:52 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Nitesh Narayan Lal <nitesh@...hat.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Eduardo Habkost <ehabkost@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 8/8] KVM: Make kvm_make_vcpus_request_mask() use
 pre-allocated cpu_kick_mask

Sean Christopherson <seanjc@...gle.com> writes:

> On Fri, Sep 03, 2021, Vitaly Kuznetsov wrote:
>> kvm_make_vcpus_request_mask() already disables preemption so just like
>> kvm_make_all_cpus_request_except() it can be switched to using
>> pre-allocated per-cpu cpumasks. This allows for improvements for both
>> users of the function: in Hyper-V emulation code 'tlb_flush' can now be
>> dropped from 'struct kvm_vcpu_hv' and kvm_make_scan_ioapic_request_mask()
>> gets rid of dynamic allocation.
>> 
>> cpumask_available() checks in kvm_make_vcpu_request() and
>> kvm_kick_many_cpus() can now be dropped as they checks for an impossible
>> condition: kvm_init() makes sure per-cpu masks are allocated.
>> 
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
>> ---
>
> Reviewed-by: Sean Christopherson <seanjc@...gle.com>
>

Thanks!

>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index a4752dcc2a75..91c1e6c98b0f 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -9224,14 +9224,8 @@ static void process_smi(struct kvm_vcpu *vcpu)
>>  void kvm_make_scan_ioapic_request_mask(struct kvm *kvm,
>>  				       unsigned long *vcpu_bitmap)
>>  {
>> -	cpumask_var_t cpus;
>> -
>> -	zalloc_cpumask_var(&cpus, GFP_ATOMIC);
>> -
>>  	kvm_make_vcpus_request_mask(kvm, KVM_REQ_SCAN_IOAPIC,
>> -				    vcpu_bitmap, cpus);
>> -
>> -	free_cpumask_var(cpus);
>> +				    vcpu_bitmap);
>
> Nit, this can all go on a single line.
>

Sorry, you've mentioned this on v4 but I forgot. Hope this can be fixed
upon commit...

>>  }
>>  
>>  void kvm_make_scan_ioapic_request(struct kvm *kvm)
>

-- 
Vitaly