linux-kernel - [PATCH 2/2] xen/x86: Increase xen_e820_map to E820_X

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Date:   Mon,  5 Dec 2016 11:49:14 -0600
From:   Alex Thorlton <athorlton@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Alex Thorlton <athorlton@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>, Russ Anderson <rja@....com>,
        David Vrabel <david.vrabel@...rix.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Denys Vlasenko <dvlasenk@...hat.com>, x86@...nel.org,
        xen-devel@...ts.xenproject.org
Subject: [PATCH 2/2] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries

On systems with sufficiently large e820 tables, and several IOAPICs, it
is possible for the XENMEM_machine_memory_map callback (and its
counterpart, XENMEM_memory_map) to attempt to return an e820 table with
more than 128 entries.  This callback adds entries to the BIOS-provided
e820 table to account for IOAPIC registers, which, on sufficiently large
systems, can result in an e820 table that is too large to copy back into
xen_e820_map.

This change simply increases the size of xen_e820_map to E820_X_MAX to
ensure that there is enough room to store the entire e820 map returned
from this callback.

Signed-off-by: Alex Thorlton <athorlton@....com>
Suggested-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Reviewed-by: Juergen Gross <jgross@...e.com>
Cc: Russ Anderson <rja@....com>
Cc: David Vrabel <david.vrabel@...rix.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: x86@...nel.org
Cc: xen-devel@...ts.xenproject.org
---
 arch/x86/xen/setup.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index f8960fc..8c394e3 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -41,7 +41,7 @@
 unsigned long xen_released_pages;
 
 /* E820 map used during setting up memory. */
-static struct e820entry xen_e820_map[E820MAX] __initdata;
+static struct e820entry xen_e820_map[E820_X_MAX] __initdata;
 static u32 xen_e820_map_entries __initdata;
 
 /*
@@ -750,7 +750,7 @@ char * __init xen_memory_setup(void)
 	max_pfn = min(max_pfn, xen_start_info->nr_pages);
 	mem_end = PFN_PHYS(max_pfn);
 
-	memmap.nr_entries = E820MAX;
+	memmap.nr_entries = ARRAY_SIZE(xen_e820_map);
 	set_xen_guest_handle(memmap.buffer, xen_e820_map);
 
 	op = xen_initial_domain() ?
@@ -923,7 +923,7 @@ char * __init xen_auto_xlated_memory_setup(void)
 	int i;
 	int rc;
 
-	memmap.nr_entries = E820MAX;
+	memmap.nr_entries = ARRAY_SIZE(xen_e820_map);
 	set_xen_guest_handle(memmap.buffer, xen_e820_map);
 
 	rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
-- 
1.8.5.6