linux-kernel - Re: [PATCH v6 07/12] Add async PF initialization to PV guest.

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Message-ID: <4CADC229.9040402@redhat.com>
Date:	Thu, 07 Oct 2010 14:50:49 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	kvm@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, hpa@...or.com,
	riel@...hat.com, cl@...ux-foundation.org, mtosatti@...hat.com
Subject: Re: [PATCH v6 07/12] Add async PF initialization to PV guest.

  On 10/04/2010 05:56 PM, Gleb Natapov wrote:
> Enable async PF in a guest if async PF capability is discovered.
>
>
> +void __cpuinit kvm_guest_cpu_init(void)
> +{
> +	if (!kvm_para_available())
> +		return;
> +
> +	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF)&&  kvmapf) {
> +		u64 pa = __pa(&__get_cpu_var(apf_reason));
> +
> +		if (native_write_msr_safe(MSR_KVM_ASYNC_PF_EN,
> +					  pa | KVM_ASYNC_PF_ENABLED, pa>>  32))

native_ versions of processor accessors shouldn't be used generally.

Also, the MSR isn't documented to fail on valid input, so you can use a 
normal wrmsrl() here.

> +			return;
> +		__get_cpu_var(apf_reason).enabled = 1;
> +		printk(KERN_INFO"KVM setup async PF for cpu %d\n",
> +		       smp_processor_id());
> +	}
> +}
> +
>
> +static int kvm_pv_reboot_notify(struct notifier_block *nb,
> +				unsigned long code, void *unused)
> +{
> +	if (code == SYS_RESTART)
> +		on_each_cpu(kvm_pv_disable_apf, NULL, 1);
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block kvm_pv_reboot_nb = {
> +	.notifier_call = kvm_pv_reboot_notify,
> +};

Does this handle kexec?

> +
> +static void kvm_guest_cpu_notify(void *dummy)
> +{
> +	if (!dummy)
> +		kvm_guest_cpu_init();
> +	else
> +		kvm_pv_disable_apf(NULL);
> +}

Why are you making decisions based on a dummy input?

The whole thing looks strange.  Use two functions?


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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