linux-kernel - Re: [PATCH v3 00/12] KVM: Add host swap event notifications for PV guest

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Message-ID: <fdaac4d51001050705s3f46dd0fi948a3b3ea803fa51@mail.gmail.com>
Date:	Wed, 6 Jan 2010 00:05:32 +0900
From:	Jun Koi <junkoi2004@...il.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	kvm@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, avi@...hat.com, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, hpa@...or.com,
	riel@...hat.com, cl@...ux-foundation.org
Subject: Re: [PATCH v3 00/12] KVM: Add host swap event notifications for PV 
	guest

On Tue, Jan 5, 2010 at 11:12 PM, Gleb Natapov <gleb@...hat.com> wrote:
> KVM virtualizes guest memory by means of shadow pages or HW assistance
> like NPT/EPT. Not all memory used by a guest is mapped into the guest
> address space or even present in a host memory at any given time.
> When vcpu tries to access memory page that is not mapped into the guest
> address space KVM is notified about it. KVM maps the page into the guest
> address space and resumes vcpu execution. If the page is swapped out
> from host memory vcpu execution is suspended till the page is not swapped
> into the memory again. This is inefficient since vcpu can do other work
> (run other task or serve interrupts) while page gets swapped in.
>
> To overcome this inefficiency this patch series implements "asynchronous
> page fault" for paravirtualized KVM guests. If a page that vcpu is
> trying to access is swapped out KVM sends an async PF to the vcpu
> and continues vcpu execution. Requested page is swapped in by another
> thread in parallel.  When vcpu gets async PF it puts faulted task to
> sleep until "wake up" interrupt is delivered. When the page is brought
> to the host memory KVM sends "wake up" interrupt and the guest's task
> resumes execution.
>

Is it true that to make this work, we will need a (PV) kernel driver
for each guest OS (Windows, Linux, ...)?

Thanks,
Jun
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