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

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Date:	Tue, 05 Jan 2010 10:59:42 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Jun Koi <junkoi2004@...il.com>
CC:	Gleb Natapov <gleb@...hat.com>, 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, cl@...ux-foundation.org
Subject: Re: [PATCH v3 00/12] KVM: Add host swap event notifications for PV
 	guest

On 01/05/2010 10:05 AM, Jun Koi wrote:
> 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, ...)?

This patch series contains the guest kernel code for Linux,
as well as the host side code.

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