linux-kernel - Re: [PATCH 2/5] KVM: arm64: Drop init_common

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Date:   Tue, 10 Aug 2021 20:41:16 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] KVM: arm64: Drop init_common_resources()



On 8/10/21 6:51 PM, Will Deacon wrote:
> On Tue, Aug 10, 2021 at 12:32:38PM +0530, Anshuman Khandual wrote:
>> Could do without this additional indirection via init_common_resources() by
>> just calling kvm_set_ipa_limit() directly instead. This change saves memory
>> and cycles.
> 
> Does it? Really?

TBH, I did not really measure them to be sure. It was more like an intuitive
assumption. But do you suspect that the compiler might be already optimizing
this out, hence giving memory and CPU cycle benefits ? Regardless this still
drops an unnecessary function.

> 
> Will
> 
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index e9a2b8f27792..19560e457c11 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -1696,11 +1696,6 @@ static bool init_psci_relay(void)
>>  	return true;
>>  }
>>  
>> -static int init_common_resources(void)
>> -{
>> -	return kvm_set_ipa_limit();
>> -}
>> -
>>  static int init_subsystems(void)
>>  {
>>  	int err = 0;
>> @@ -2102,7 +2097,7 @@ int kvm_arch_init(void *opaque)
>>  		}
>>  	}
>>  
>> -	err = init_common_resources();
>> +	err = kvm_set_ipa_limit();
>>  	if (err)
>>  		return err;
>>  
>> -- 
>> 2.20.1
>>