linux-kernel - [PATCH 10/11] xen/m2p: No need to catch exceptions when we know that there is no RAM

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Date:	Mon, 31 Jan 2011 17:44:35 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	linux-kernel@...r.kernel.org, Xen-devel@...ts.xensource.com,
	konrad@...nel.org, jeremy@...p.org
Cc:	hpa@...or.com, stefano.stabellini@...citrix.com,
	Ian.Campbell@...citrix.com,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH 10/11] xen/m2p: No need to catch exceptions when we know that there is no RAM

. beyound what we think is the end of memory. However there might
be more System RAM - but assigned to a guest. Hence jump to the
M2P override check and consult.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
 arch/x86/include/asm/xen/page.h |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 7b17fc5..ed46ec2 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -85,6 +85,10 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return mfn;
 
+	if (unlikely((mfn >> machine_to_phys_order) != 0)) {
+		pfn = ~0;
+		goto try_override;
+	}
 	pfn = 0;
 	/*
 	 * The array access can fail (e.g., device space beyond end of RAM).
@@ -92,7 +96,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
 	 * but we must handle the fault without crashing!
 	 */
 	__get_user(pfn, &machine_to_phys_mapping[mfn]);
-
+try_override:
 	/*
 	 * If this appears to be a foreign mfn (because the pfn
 	 * doesn't map back to the mfn), then check the local override
-- 
1.7.1

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