[RFC PATCH 11/12] x86/xen: close event channels for PIRQs in system core suspend callback

Anchal Agarwal
2018-06-12T20:56:18Z

From: Munehisa Kamata <kamatam@amazon.com>

Close event channels allocated for devices which are backed by PIRQ and
still active when suspending the system core. Normally, the devices are
emulated legacy devices, e.g. PS/2 keyboard, floppy controller and etc.

Without this, in PM hibernation, information about the event channel
remains in hibernation image, but there is no guarantee that the same
event channel numbers are assigned to the devices when restoring the
system. This may cause conflict like the following and prevent some
devices from being restored correctly.

[ 102.330821] ------------[ cut here ]------------
[ 102.333264] WARNING: CPU: 0 PID: 2324 at
drivers/xen/events/events_base.c:878 bind_evtchn_to_irq+0x88/0xf0
...
[ 102.348057] Call Trace:
[ 102.348057] [<ffffffff813001df>] dump_stack+0x63/0x84
[ 102.348057] [<ffffffff81071811>] __warn+0xd1/0xf0
[ 102.348057] [<ffffffff810718fd>] warn_slowpath_null+0x1d/0x20
[ 102.348057] [<ffffffff8139a1f8>] bind_evtchn_to_irq+0x88/0xf0
[ 102.348057] [<ffffffffa00cd420>] ? blkif_copy_from_grant+0xb0/0xb0 [xen_blkfront]
[ 102.348057] [<ffffffff8139a307>] bind_evtchn_to_irqhandler+0x27/0x80
[ 102.348057] [<ffffffffa00cc785>] talk_to_blkback+0x425/0xcd0 [xen_blkfront]
[ 102.348057] [<ffffffff811e0c8a>] ? __kmalloc+0x1ea/0x200
[ 102.348057] [<ffffffffa00ce84d>] blkfront_restore+0x2d/0x60 [xen_blkfront]
[ 102.348057] [<ffffffff813a0078>] xenbus_dev_restore+0x58/0x100
[ 102.348057] [<ffffffff813a1ff0>] ? xenbus_frontend_delayed_resume+0x20/0x20
[ 102.348057] [<ffffffff813a200e>] xenbus_dev_cond_restore+0x1e/0x30
[ 102.348057] [<ffffffff813f797e>] dpm_run_callback+0x4e/0x130
[ 102.348057] [<ffffffff813f7f17>] device_resume+0xe7/0x210
[ 102.348057] [<ffffffff813f7810>] ? pm_dev_dbg+0x80/0x80
[ 102.348057] [<ffffffff813f9374>] dpm_resume+0x114/0x2f0
[ 102.348057] [<ffffffff810c00cf>] hibernation_snapshot+0x15f/0x380
[ 102.348057] [<ffffffff810c0ac3>] hibernate+0x183/0x290
[ 102.348057] [<ffffffff810be1af>] state_store+0xcf/0xe0
[ 102.348057] [<ffffffff813020bf>] kobj_attr_store+0xf/0x20
[ 102.348057] [<ffffffff8127c88a>] sysfs_kf_write+0x3a/0x50
[ 102.348057] [<ffffffff8127c3bb>] kernfs_fop_write+0x10b/0x190
[ 102.348057] [<ffffffff81200008>] __vfs_write+0x28/0x120
[ 102.348057] [<ffffffff81200c19>] ? rw_verify_area+0x49/0xb0
[ 102.348057] [<ffffffff81200e62>] vfs_write+0xb2/0x1b0
[ 102.348057] [<ffffffff81202196>] SyS_write+0x46/0xa0
[ 102.348057] [<ffffffff81520cf7>] entry_SYSCALL_64_fastpath+0x1a/0xa9
[ 102.423005] ---[ end trace b8d6718e22e2b107 ]---
[ 102.425031] genirq: Flags mismatch irq 6. 00000000 (blkif) vs. 00000000 (floppy)

Note that we don't explicitly re-allocate event channels for such
devices in the resume callback. Re-allocation will occur when PM core
re-enable IRQs for the devices at later point.

Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
Reviewed-by: Munehisa Kamata <kamatam@amazon.com>
Reviewed-by: Eduardo Valentin <eduval@amazon.com>
---
arch/x86/xen/suspend.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
index dae0f74..affa63d 100644
--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -105,6 +105,8 @@ static int xen_syscore_suspend(void)
xen_save_steal_clock(cpu);
}

+ xen_shutdown_pirqs();
+
xrfp.domid = DOMID_SELF;
xrfp.gpfn = __pa(HYPERVISOR_shared_info) >> PAGE_SHIFT;

--
2.7.4