linux-kernel - Re: [PATCH 2/2] KVM: MMU: Use base

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Message-ID: <4C922302.20900@redhat.com>
Date:	Thu, 16 Sep 2010 16:00:34 +0200
From:	Avi Kivity <avi@...hat.com>
To:	"Roedel, Joerg" <Joerg.Roedel@....com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] KVM: MMU: Use base_role.nxe for mmu.nx

  On 09/15/2010 10:48 AM, Roedel, Joerg wrote:
> On Tue, Sep 14, 2010 at 06:08:37PM -0400, Marcelo Tosatti wrote:
> >
> >  For tdp better set base_role.nxe to zero, otherwise duplicate tdp
> >  pagetables can be created if the guest switches between nx/non-nx.
> >
>
> This does not work because bit 63 is marked as reserved if base_role.nxe
> is 0. If the walk_addr_generic function then runs with tdp enabled it
> would report a set nx bit as a rsvd fault.
> We also can't use is_nx() in those path because it does not distinguish
> between l1 and l2 nx. Are there guests that switch the efer.nx bit
> regularly enough so that it matters? If so I would suggest to drop this
> patch and keep mmu.nx.
>
>

I'll do that then.  I'm still unhappy about the duplication.

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

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