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From: Anchal Agarwal <anchalag@amazon.com>
To: <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>,
	<hpa@zytor.com>,  <x86@kernel.org>, <boris.ostrovsky@oracle.com>,
	<jgross@suse.com>, <linux-pm@vger.kernel.org>,
	<linux-mm@kvack.org>, <kamatam@amazon.com>,
	<sstabellini@kernel.org>, <konrad.wilk@oracle.com>,
	<roger.pau@citrix.com>, <axboe@kernel.dk>, <davem@davemloft.net>,
	<rjw@rjwysocki.net>, <len.brown@intel.com>, <pavel@ucw.cz>,
	<peterz@infradead.org>, <eduval@amazon.com>, <sblbir@amazon.com>,
	<anchalag@amazon.com>, <xen-devel@lists.xenproject.org>,
	<vkuznets@redhat.com>, <netdev@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <dwmw@amazon.co.uk>,
	<fllinden@amaozn.com>, <benh@kernel.crashing.org>
Subject: [Xen-devel] [RFC PATCH v3 01/12] xen/manage: keep track of the on-going suspend mode
Date: Fri, 14 Feb 2020 23:22:08 +0000
Message-ID: <36567b7204db25d7307a165a6565837a213efdf8.1581721799.git.anchalag@amazon.com> (raw)
In-Reply-To: <cover.1581721799.git.anchalag@amazon.com>

From: Munehisa Kamata <kamatam@amazon.com>

Guest hibernation is different from xen suspend/resume/live migration.
Xen save/restore does not use pm_ops as is needed by guest hibernation.
Hibernation in guest follows ACPI path and is guest inititated , the
hibernation image is saved within guest as compared to later modes
which are xen toolstack assisted and image creation/storage is in
control of hypervisor/host machine.
To differentiate between Xen suspend and PM hibernation, keep track
of the on-going suspend mode by mainly using a new PM notifier.
Introduce simple functions which help to know the on-going suspend mode
so that other Xen-related code can behave differently according to the
current suspend mode.
Since Xen suspend doesn't have corresponding PM event, its main logic
is modfied to acquire pm_mutex and set the current mode.

Though, acquirng pm_mutex is still right thing to do, we may
see deadlock if PM hibernation is interrupted by Xen suspend.
PM hibernation depends on xenwatch thread to process xenbus state
transactions, but the thread will sleep to wait pm_mutex which is
already held by PM hibernation context in the scenario. Xen shutdown
code may need some changes to avoid the issue.

[Anchal Changelog: Merged patch xen/manage: introduce helper function
to know the on-going suspend mode into this one for better readability]
Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
---
 drivers/xen/manage.c  | 73 +++++++++++++++++++++++++++++++++++++++++++
 include/xen/xen-ops.h |  3 ++
 2 files changed, 76 insertions(+)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index cd046684e0d1..0b30ab522b77 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -14,6 +14,7 @@
 #include <linux/freezer.h>
 #include <linux/syscore_ops.h>
 #include <linux/export.h>
+#include <linux/suspend.h>
 
 #include <xen/xen.h>
 #include <xen/xenbus.h>
@@ -40,6 +41,31 @@ enum shutdown_state {
 /* Ignore multiple shutdown requests. */
 static enum shutdown_state shutting_down = SHUTDOWN_INVALID;
 
+enum suspend_modes {
+	NO_SUSPEND = 0,
+	XEN_SUSPEND,
+	PM_SUSPEND,
+	PM_HIBERNATION,
+};
+
+/* Protected by pm_mutex */
+static enum suspend_modes suspend_mode = NO_SUSPEND;
+
+bool xen_suspend_mode_is_xen_suspend(void)
+{
+	return suspend_mode == XEN_SUSPEND;
+}
+
+bool xen_suspend_mode_is_pm_suspend(void)
+{
+	return suspend_mode == PM_SUSPEND;
+}
+
+bool xen_suspend_mode_is_pm_hibernation(void)
+{
+	return suspend_mode == PM_HIBERNATION;
+}
+
 struct suspend_info {
 	int cancelled;
 };
@@ -99,6 +125,10 @@ static void do_suspend(void)
 	int err;
 	struct suspend_info si;
 
+	lock_system_sleep();
+
+	suspend_mode = XEN_SUSPEND;
+
 	shutting_down = SHUTDOWN_SUSPEND;
 
 	err = freeze_processes();
@@ -162,6 +192,10 @@ static void do_suspend(void)
 	thaw_processes();
 out:
 	shutting_down = SHUTDOWN_INVALID;
+
+	suspend_mode = NO_SUSPEND;
+
+	unlock_system_sleep();
 }
 #endif	/* CONFIG_HIBERNATE_CALLBACKS */
 
@@ -387,3 +421,42 @@ int xen_setup_shutdown_event(void)
 EXPORT_SYMBOL_GPL(xen_setup_shutdown_event);
 
 subsys_initcall(xen_setup_shutdown_event);
+
+static int xen_pm_notifier(struct notifier_block *notifier,
+			   unsigned long pm_event, void *unused)
+{
+	switch (pm_event) {
+	case PM_SUSPEND_PREPARE:
+		suspend_mode = PM_SUSPEND;
+		break;
+	case PM_HIBERNATION_PREPARE:
+	case PM_RESTORE_PREPARE:
+		suspend_mode = PM_HIBERNATION;
+		break;
+	case PM_POST_SUSPEND:
+	case PM_POST_RESTORE:
+	case PM_POST_HIBERNATION:
+		/* Set back to the default */
+		suspend_mode = NO_SUSPEND;
+		break;
+	default:
+		pr_warn("Receive unknown PM event 0x%lx\n", pm_event);
+		return -EINVAL;
+	}
+
+	return 0;
+};
+
+static struct notifier_block xen_pm_notifier_block = {
+	.notifier_call = xen_pm_notifier
+};
+
+static int xen_setup_pm_notifier(void)
+{
+	if (!xen_hvm_domain())
+		return -ENODEV;
+
+	return register_pm_notifier(&xen_pm_notifier_block);
+}
+
+subsys_initcall(xen_setup_pm_notifier);
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index d89969aa9942..6c36e161dfd1 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -40,6 +40,9 @@ u64 xen_steal_clock(int cpu);
 
 int xen_setup_shutdown_event(void);
 
+bool xen_suspend_mode_is_xen_suspend(void);
+bool xen_suspend_mode_is_pm_suspend(void);
+bool xen_suspend_mode_is_pm_hibernation(void);
 extern unsigned long *xen_contiguous_bitmap;
 
 #if defined(CONFIG_XEN_PV) || defined(CONFIG_ARM) || defined(CONFIG_ARM64)
-- 
2.24.1.AMZN


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Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14 23:21 [Xen-devel] [RFC RESEND PATCH v3 00/12] Enable PM hibernation on guest VMs Anchal Agarwal
2020-02-14 23:22 ` Anchal Agarwal [this message]
2020-02-14 23:23 ` [Xen-devel] [RFC PATCH v3 02/12] xenbus: add freeze/thaw/restore callbacks support Anchal Agarwal
2020-02-14 23:23 ` [Xen-devel] [RFC PATCH v3 03/12] x86/xen: Introduce new function to map HYPERVISOR_shared_info on Resume Anchal Agarwal
2020-02-14 23:24 ` [Xen-devel] [RFC PATCH v3 04/12] x86/xen: add system core suspend and resume callbacks Anchal Agarwal
2020-02-14 23:24 ` [Xen-devel] [RFC PATCH v3 05/12] xen-netfront: add callbacks for PM suspend and hibernation support Anchal Agarwal
2020-02-14 23:25 ` [Xen-devel] [RFC PATCH v3 06/12] xen-blkfront: add callbacks for PM suspend and hibernation Anchal Agarwal
2020-02-17 10:05   ` Roger Pau Monné
2020-02-17 23:05     ` Anchal Agarwal
2020-02-18  9:16       ` Roger Pau Monné
2020-02-19 18:04         ` Anchal Agarwal
2020-02-20  8:39           ` Roger Pau Monné
2020-02-20  8:54             ` Durrant, Paul
2020-02-20 15:45               ` Roger Pau Monné
2020-02-20 16:23                 ` Durrant, Paul
2020-02-20 16:48                   ` Roger Pau Monné
2020-02-20 17:01                     ` Durrant, Paul
2020-02-14 23:25 ` [Xen-devel] [RFC PATCH v3 07/12] genirq: Shutdown irq chips in suspend/resume during hibernation Anchal Agarwal
2020-02-14 23:26 ` [Xen-devel] [RFC PATCH v3 08/12] xen/time: introduce xen_{save, restore}_steal_clock Anchal Agarwal
2020-02-14 23:27 ` [Xen-devel] [RFC PATCH v3 09/12] x86/xen: save and restore steal clock Anchal Agarwal
2020-02-14 23:27 ` [Xen-devel] [RFC PATCH v3 10/12] xen: Introduce wrapper for save/restore sched clock offset Anchal Agarwal
2020-02-14 23:27 ` [Xen-devel] [RFC PATCH v3 11/12] xen: Update sched clock offset to avoid system instability in hibernation Anchal Agarwal
2020-02-14 23:28 ` [Xen-devel] [RFC PATCH v3 12/12] PM / hibernate: update the resume offset on SNAPSHOT_SET_SWAP_AREA Anchal Agarwal
  -- strict thread matches above, loose matches on Subject: below --
2020-02-12 22:30 [Xen-devel] [RFC PATCH v3 01/12] xen/manage: keep track of the on-going suspend mode Anchal Agarwal

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