linux-kernel - Re: [PATCH v2 08/12] Inject asynchronous page fault into a guest if page is swapped out.

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Message-ID: <4B0D2B22.4030403@redhat.com>
Date:	Wed, 25 Nov 2009 15:03:30 +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
Subject: Re: [PATCH v2 08/12] Inject asynchronous page fault into a guest
 if page is swapped out.

On 11/23/2009 04:06 PM, Gleb Natapov wrote:
> If guest access swapped out memory do not swap it in from vcpu thread
> context. Setup slow work to do swapping and send async page fault to
> a guest.
>
> Allow async page fault injection only when guest is in user mode since
> otherwise guest may be in non-sleepable context and will not be able to
> reschedule.
>
> +
> +void kvm_arch_inject_async_page_present(struct kvm_vcpu *vcpu,
> +					struct kvm_async_pf *work)
> +{
> +	put_user(KVM_PV_REASON_PAGE_READY, vcpu->arch.apf_data);
> +	kvm_inject_page_fault(vcpu, work->arch.token, 0);
> +	trace_kvm_send_async_pf(work->arch.token, work->gva,
> +				KVM_PV_REASON_PAGE_READY);
> +}
>    

What if the guest is now handling a previous asynv pf or ready 
notification?  We're clobbering the data structure.

> +
> +bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu)
> +{
> +	return !kvm_event_needs_reinjection(vcpu)&&
> +		kvm_x86_ops->interrupt_allowed(vcpu);
> +}
>    

Okay, so this is only allowed with interrupts disabled.  Need to make 
sure the entire pf path up to async pf executes with interrupts disabled.

-- 
error compiling committee.c: too many arguments to function

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