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xen-devel
[Xen-devel] Re: [PATCH 7/8] xen/mmu: Introduce IDENTITY_FRAME_BIT
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To: |
Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH 7/8] xen/mmu: Introduce IDENTITY_FRAME_BIT |
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From: |
Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> |
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Date: |
Tue, 4 Jan 2011 11:45:44 -0500 |
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Cc: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>, "hpa@xxxxxxxxx" <hpa@xxxxxxxxx> |
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Delivery-date: |
Tue, 04 Jan 2011 08:47:56 -0800 |
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<1294158375.3831.490.camel@xxxxxxxxxxxxxxxxxxxxxx> |
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References: |
<1293738517-7287-1-git-send-email-konrad.wilk@xxxxxxxxxx> <1293738517-7287-8-git-send-email-konrad.wilk@xxxxxxxxxx> <1294158375.3831.490.camel@xxxxxxxxxxxxxxxxxxxxxx> |
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Mutt/1.5.20 (2009-06-14) |
On Tue, Jan 04, 2011 at 04:26:15PM +0000, Ian Campbell wrote:
> On Thu, 2010-12-30 at 19:48 +0000, Konrad Rzeszutek Wilk wrote:
> > @@ -52,9 +53,12 @@ static inline unsigned long pfn_to_mfn(unsigned long pfn)
> >
> > mfn = get_phys_to_machine(pfn);
> >
> > - if (mfn != INVALID_P2M_ENTRY)
> > + if (mfn != INVALID_P2M_ENTRY) {
> > mfn &= ~FOREIGN_FRAME_BIT;
> >
> > + if (mfn & IDENTITY_FRAME_BIT)
> > + mfn &= ~IDENTITY_FRAME_BIT;
> > + }
>
> I don't think the inner-if buys us anything here and the whole thing is
> equivalent to:
> if (mfn != INVALID_P2M_ENTRY)
> mfn &= ~(FOREIGN_FRAME_BIT|IDENTITY_FRAME_BIT);
>
> Not sure if the FOREIGN_FRAME_BIT|IDENTITY_FRAME_BIT construct gets
> enough use to be worthy of a #define FRAME_TYPE_MASK etc.
Yeah, that is much better.
>
> > return mfn;
> > }
> >
> > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> > index d98bd43..d470435 100644
> > --- a/arch/x86/xen/mmu.c
> > +++ b/arch/x86/xen/mmu.c
> > @@ -425,10 +425,10 @@ unsigned long get_phys_to_machine(unsigned long pfn)
> > * would be wrong.
> > */
> > if (p2m_top[topidx] == p2m_mid_identity)
> > - return pfn;
> > + return pfn | IDENTITY_FRAME_BIT;
>
> It's probably worth defining IDENTITY_FRAME(m) in the pattern of
> FOREIGN_FRAME(m).
<nods>
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