linux-kernel - Re: [PATCH] kvm: allow RO page when atomic && !write

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Message-ID: <20110222192412.GA7645@amt.cnet>
Date:	Tue, 22 Feb 2011 16:24:12 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH] kvm: allow RO page when atomic && !write_fault

On Mon, Feb 21, 2011 at 11:47:36AM +0800, Lai Jiangshan wrote:
> 
> Atomic-able hva_to_pfn() patches and allow-read-only-page patches
> are merged almost the same time. But hva_to_pfn() does not handle
> these two issues well together.
> 
> When @atomic && !@...te_fault && host-is-read-only-page-mapped
> the code will return fault_page, actually, it will be better
> if we return the pfn of the read-only-page.
> 
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>

Lai,

For pte prefetch, user of atomic hva_to_pfn, the write_fault parameter
is meaningless (since that information is only available for the pte
being faulted).

Returning fault page for a read-only page is useful so that pte prefetch
is aborted.

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