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Subject[PATCH 2/4] xen: support CONFIG_MAXSMP
Date
From: Andrew Jones <drjones@redhat.com>

The MAXSMP config option requires CPUMASK_OFFSTACK, which in turn
requires we init the memory for the maps while we bring up the cpus.
MAXSMP also increases NR_CPUS to 4096. This increase in size exposed an
issue in the argument construction for multicalls from
xen_flush_tlb_others. The args should only need space for the actual
number of cpus.

Also in 2.6.39 it exposes a bootup problem.

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8157a1d3>] set_cpu_sibling_map+0x123/0x30d
...
Call Trace:
[<ffffffff81039a3f>] ? xen_restore_fl_direct_reloc+0x4/0x4
[<ffffffff819dc4db>] xen_smp_prepare_cpus+0x36/0x135
..

CC: stable@kernel.org
Signed-off-by: Andrew Jones <drjones@redhat.com>
[v2: Updated to compile on 3.0]
[v3: Updated to compile when CONFIG_SMP is not defined]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
arch/x86/xen/mmu.c | 3 ++-
arch/x86/xen/smp.c | 7 +++++++
2 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index afe1d54..673e968 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -59,6 +59,7 @@
#include <asm/page.h>
#include <asm/init.h>
#include <asm/pat.h>
+#include <asm/smp.h>

#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
@@ -1231,7 +1232,7 @@ static void xen_flush_tlb_others(const struct cpumask *cpus,
{
struct {
struct mmuext_op op;
- DECLARE_BITMAP(mask, NR_CPUS);
+ DECLARE_BITMAP(mask, num_processors);
} *args;
struct multicall_space mcs;

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 41038c0..b4533a8 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -205,11 +205,18 @@ static void __init xen_smp_prepare_boot_cpu(void)
static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
{
unsigned cpu;
+ unsigned int i;

xen_init_lock_cpu(0);

smp_store_cpu_info(0);
cpu_data(0).x86_max_cores = 1;
+
+ for_each_possible_cpu(i) {
+ zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
+ zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
+ zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
+ }
set_cpu_sibling_map(0);

if (xen_smp_intr_init(0))
--
1.7.4.1


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