linux-kernel - [PATCH] xen/p2m: fix extra memory regions accounting

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Date:	Thu, 3 Sep 2015 14:05:15 +0200
From:	Roger Pau Monne <roger.pau@...rix.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Roger Pau Monne <roger.pau@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	"David Vrabel" <david.vrabel@...rix.com>,
	Juergen Gross <jgross@...e.com>,
	<xen-devel@...ts.xenproject.org>
Subject: [PATCH] xen/p2m: fix extra memory regions accounting

On systems with memory maps with ranges that don't end at page boundaries,
like:

[...]
(XEN)  0000000000100000 - 00000000dfdf9c00 (usable)
(XEN)  00000000dfdf9c00 - 00000000dfe4bc00 (ACPI NVS)
[...]

xen_add_extra_mem will create a protected range that ends up at 0xdfdf9c00,
but the function used to check if a memory address is inside of a protected
range works with pfns, which means that an attempt to map 0xdfdf9c00 will be
refused because the check is performed against 0xdfdf9000 instead of
0xdfdf9c00.

In order to fix this, make sure that the ranges that are added to the
xen_extra_mem array are aligned to page boundaries.

Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: David Vrabel <david.vrabel@...rix.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: xen-devel@...ts.xenproject.org
---
AFAICT this patch needs to be backported to 3.19, 4.0, 4.1 and 4.2.
---
 arch/x86/xen/setup.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 55f388e..dcf5865 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -68,6 +68,9 @@ static void __init xen_add_extra_mem(phys_addr_t start, phys_addr_t size)
 {
 	int i;
 
+	start = PAGE_ALIGN(start);
+	size &= PAGE_MASK;
+
 	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
 		/* Add new region. */
 		if (xen_extra_mem[i].size == 0) {
@@ -92,6 +95,9 @@ static void __init xen_del_extra_mem(phys_addr_t start, phys_addr_t size)
 	int i;
 	phys_addr_t start_r, size_r;
 
+	start = PAGE_ALIGN(start);
+	size &= PAGE_MASK;
+
 	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
 		start_r = xen_extra_mem[i].start;
 		size_r = xen_extra_mem[i].size;
-- 
1.9.5 (Apple Git-50.3)

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