linux-kernel - Re: [PATCH v6 06/12] Add PV MSR to enable asynchronous page faults delivery.

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Message-ID: <4CB0B7C5.5030609@redhat.com>
Date:	Sat, 09 Oct 2010 20:43:17 +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 06/12] Add PV MSR to enable asynchronous page faults
 delivery.

  On 10/07/2010 07:59 PM, Gleb Natapov wrote:
> On Thu, Oct 07, 2010 at 02:58:26PM +0200, Avi Kivity wrote:
> >   On 10/04/2010 05:56 PM, Gleb Natapov wrote:
> >  >+
> >  >+	Physical address points to 32 bit memory location that will be written
> >  >+	to by the hypervisor at the time of asynchronous page fault injection to
> >  >+	indicate type of asynchronous page fault. Value of 1 means that the page
> >  >+	referred to by the page fault is not present. Value 2 means that the
> >  >+	page is now available.
> >
> >  "The must not enable interrupts before the reason is read, or it may
> >  be overwritten by another apf".
> >
> >  Document the fact that disabling interrupts disables APFs.
> >
> >  How does the guest distinguish betweem APFs and ordinary page faults?
> >
> >  What's the role of cr2?
> >
> >  When disabling APF, all pending APFs are flushed and may or may not
> >  get a completion.
> >
> >  Is a "page available" notification guaranteed to arrive on the same
> >  vcpu that took the "page not present" fault?
> >
> You mean documentation is lacking? :)
>

I mean you should be able to write guest support code without reading 
the host code, just the documentation.

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

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