linux-kernel - Re: [PATCH v2 5/5] KVM: refactor asynchronous vcpu ioctl dispatch

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Date:	Thu, 13 Aug 2015 10:53:57 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2 5/5] KVM: refactor asynchronous vcpu ioctl dispatch

2015-08-12 22:03+0200, Christian Borntraeger:
> Am 05.08.2015 um 18:33 schrieb Radim Krčmář:
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> @@ -2252,12 +2252,15 @@ static long kvm_vcpu_ioctl(struct file *filp,
>>  	 * Special cases: vcpu ioctls that are asynchronous to vcpu execution,
>>  	 * so vcpu_load() would break it.
>>  	 */
>> +	switch (ioctl) {
>>  #if defined(CONFIG_S390) || defined(CONFIG_PPC) || defined(CONFIG_MIPS)
>> -	if (ioctl == KVM_S390_INTERRUPT || ioctl == KVM_S390_IRQ || ioctl == KVM_INTERRUPT)
>> -		return kvm_arch_vcpu_ioctl(filp, ioctl, arg);
>> +	case KVM_S390_INTERRUPT:
>> +	case KVM_S390_IRQ:
>> +	case KVM_INTERRUPT:
> 
> When you are it you might want to put the KVM_S390* withing CONFIG_S390 and
> KVM_INTERRUPT within CONFIG_PPC || CONFIG_MIPS

Sure, thanks.

> This might speed up the switch statement for s390/ppc/mips a tiny bit. It will add
> another ifdef, though. Paolo?

For v3, I will name the decision as an inline function, which should
make the #ifing more acceptable (at the cost of not having ioctls #defs
in the body of kvm_vcpu_ioctl).  Something like this,

static inline bool kvm_asynchronous_ioctl(unsigned ioctl)
{
	switch (ioctl) {
#if defined(CONFIG_S390)
	case KVM_S390_INTERRUPT:
	case KVM_S390_IRQ:
#endif
#if defined(CONFIG_MIPS)
	case KVM_INTERRUPT:
#endif
	case KVM_USER_EXIT:
		return true;
	}
	return false;
}

[...]
	if (kvm_asynchronous_ioctl(ioctl))
		return kvm_arch_vcpu_ioctl(filp, ioctl, arg);
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