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| author | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2012-04-26 21:50:03 +0400 |
|---|---|---|
| committer | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2012-04-27 06:07:21 +0400 |
| commit | cf405ae612b0f7e2358db7ff594c0e94846137aa (patch) | |
| tree | 5f3540aa675a25325c318da47d02853fe8b79043 /arch | |
| parent | 521394e4e679996955bc351cb6b64639751db2ff (diff) | |
| download | linux-cf405ae612b0f7e2358db7ff594c0e94846137aa.tar.xz | |
xen/smp: Fix crash when booting with ACPI hotplug CPUs.
When we boot on a machine that can hotplug CPUs and we
are using 'dom0_max_vcpus=X' on the Xen hypervisor line
to clip the amount of CPUs available to the initial domain,
we get this:
(XEN) Command line: com1=115200,8n1 dom0_mem=8G noreboot dom0_max_vcpus=8 sync_console mce_verbosity=verbose console=com1,vga loglvl=all guest_loglvl=all
.. snip..
DMI: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.99.99.x032.072520111118 07/25/2011
.. snip.
SMP: Allowing 64 CPUs, 32 hotplug CPUs
installing Xen timer for CPU 7
cpu 7 spinlock event irq 361
NMI watchdog: disabled (cpu7): hardware events not enabled
Brought up 8 CPUs
.. snip..
[acpi processor finds the CPUs are not initialized and starts calling
arch_register_cpu, which creates /sys/devices/system/cpu/cpu8/online]
CPU 8 got hotplugged
CPU 9 got hotplugged
CPU 10 got hotplugged
.. snip..
initcall 1_acpi_battery_init_async+0x0/0x1b returned 0 after 406 usecs
calling erst_init+0x0/0x2bb @ 1
[and the scheduler sticks newly started tasks on the new CPUs, but
said CPUs cannot be initialized b/c the hypervisor has limited the
amount of vCPUS to 8 - as per the dom0_max_vcpus=8 flag.
The spinlock tries to kick the other CPU, but the structure for that
is not initialized and we crash.]
BUG: unable to handle kernel paging request at fffffffffffffed8
IP: [<ffffffff81035289>] xen_spin_lock+0x29/0x60
PGD 180d067 PUD 180e067 PMD 0
Oops: 0002 [#1] SMP
CPU 7
Modules linked in:
Pid: 1, comm: swapper/0 Not tainted 3.4.0-rc2upstream-00001-gf5154e8 #1 Intel Corporation S2600CP/S2600CP
RIP: e030:[<ffffffff81035289>] [<ffffffff81035289>] xen_spin_lock+0x29/0x60
RSP: e02b:ffff8801fb9b3a70 EFLAGS: 00010282
With this patch, we cap the amount of vCPUS that the initial domain
can run, to exactly what dom0_max_vcpus=X has specified.
In the future, if there is a hypercall that will allow a running
domain to expand past its initial set of vCPUS, this patch should
be re-evaluated.
CC: stable@kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/xen/smp.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index 5fac6919b957..0503c0c493a9 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -178,6 +178,7 @@ static void __init xen_fill_possible_map(void) static void __init xen_filter_cpu_maps(void) { int i, rc; + unsigned int subtract = 0; if (!xen_initial_domain()) return; @@ -192,8 +193,22 @@ static void __init xen_filter_cpu_maps(void) } else { set_cpu_possible(i, false); set_cpu_present(i, false); + subtract++; } } +#ifdef CONFIG_HOTPLUG_CPU + /* This is akin to using 'nr_cpus' on the Linux command line. + * Which is OK as when we use 'dom0_max_vcpus=X' we can only + * have up to X, while nr_cpu_ids is greater than X. This + * normally is not a problem, except when CPU hotplugging + * is involved and then there might be more than X CPUs + * in the guest - which will not work as there is no + * hypercall to expand the max number of VCPUs an already + * running guest has. So cap it up to X. */ + if (subtract) + nr_cpu_ids = nr_cpu_ids - subtract; +#endif + } static void __init xen_smp_prepare_boot_cpu(void) |