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* [Xen-devel] [RFC PATCH v3 10/12] xen: Introduce wrapper for save/restore sched clock offset
@ 2020-02-12 22:34 Anchal Agarwal
  0 siblings, 0 replies; 2+ messages in thread
From: Anchal Agarwal @ 2020-02-12 22:34 UTC (permalink / raw)
  To: tglx, mingo, bp, hpa, x86, boris.ostrovsky, jgross, linux-pm,
	linux-mm, kamatam, sstabellini, konrad.wilk, roger.pau, axboe,
	davem, rjw, len.brown, pavel, peterz, eduval, sblbir, anchalag,
	xen-devel, vkuznets, netdev, linux-kernel, dwmw, fllinden, benh

Introduce wrappers for save/restore xen_sched_clock_offset to be
used by PM hibernation code to avoid system instability during resume.

Signed-off-by: Anchal Agarwal <anchalag@amazon.com>

---
Changes since V2:
* Dropped marking tsc unstable during hibernation patch
* Fixed issue with xen_sched_clock_offset during suspend/resume
* On further interrogation and testing, the issue wasn't with tsc
being stable/unstable

---
 arch/x86/xen/time.c    | 15 +++++++++++++--
 arch/x86/xen/xen-ops.h |  2 ++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 8cf632dda605..eeb6d3d2eaab 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -379,12 +379,23 @@ static const struct pv_time_ops xen_time_ops __initconst = {
 static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
 static u64 xen_clock_value_saved;
 
+/*This is needed to maintain a monotonic clock value during PM hibernation */
+void xen_save_sched_clock_offset(void)
+{
+	xen_clock_value_saved = xen_clocksource_read() - xen_sched_clock_offset;
+}
+
+void xen_restore_sched_clock_offset(void)
+{
+	xen_sched_clock_offset = xen_clocksource_read() - xen_clock_value_saved;
+}
+
 void xen_save_time_memory_area(void)
 {
 	struct vcpu_register_time_memory_area t;
 	int ret;
 
-	xen_clock_value_saved = xen_clocksource_read() - xen_sched_clock_offset;
+	xen_save_sched_clock_offset();
 
 	if (!xen_clock)
 		return;
@@ -426,7 +437,7 @@ void xen_restore_time_memory_area(void)
 out:
 	/* Need pvclock_resume() before using xen_clocksource_read(). */
 	pvclock_resume();
-	xen_sched_clock_offset = xen_clocksource_read() - xen_clock_value_saved;
+	xen_restore_sched_clock_offset();
 }
 
 static void xen_setup_vsyscall_time_info(void)
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index d84c357994bd..9f49124df033 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -72,6 +72,8 @@ void xen_save_time_memory_area(void);
 void xen_restore_time_memory_area(void);
 void xen_init_time_ops(void);
 void xen_hvm_init_time_ops(void);
+void xen_save_sched_clock_offset(void);
+void xen_restore_sched_clock_offset(void);
 
 irqreturn_t xen_debug_interrupt(int irq, void *dev_id);
 
-- 
2.24.1.AMZN


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^ permalink raw reply	[flat|nested] 2+ messages in thread
* [Xen-devel] [RFC RESEND PATCH v3 00/12] Enable PM hibernation on guest VMs
@ 2020-02-14 23:21 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
  0 siblings, 1 reply; 2+ messages in thread
From: Anchal Agarwal @ 2020-02-14 23:21 UTC (permalink / raw)
  To: tglx, mingo, bp, hpa, x86, boris.ostrovsky, jgross, linux-pm,
	linux-mm, kamatam, sstabellini, konrad.wilk, roger.pau, axboe,
	davem, rjw, len.brown, pavel, peterz, eduval, sblbir, anchalag,
	xen-devel, vkuznets, netdev, linux-kernel, dwmw, fllinden, benh

Resending this in a more threaded format.
  
Hello,
I am sending out a v3 version of series of patches that implements guest
PM hibernation.
These guests are running on xen hypervisor. The patches had been tested
against mainstream kernel. EC2 instance hibernation feature is provided
to the AWS EC2 customers. PM hibernation uses swap space carved out within
the guest[or can be a separate partition], where hibernation image is
stored and restored from.

Doing guest hibernation does not involve any support from hypervisor and
this way guest has complete control over its state. Infrastructure
restrictions for saving up guest state can be overcome by guest initiated
hibernation.

This series includes some improvements over RFC series sent last year:
https://lists.xenproject.org/archives/html/xen-devel/2018-06/msg00823.html

Changelog v3:
1. Feedback from V2
2. Introduced 2 new patches for xen sched clock offset fix
3. Fixed pirq shutdown/restore in generic irq subsystem
4. Split save/restore steal clock patches into 2 for better readability

Changelog v2:
1. Removed timeout/request present on the ring in xen-blkfront during blkfront freeze
2. Fixed restoring of PIRQs which was apparently working for 4.9 kernels but not for
newer kernel. [Legacy irqs were no longer restored after hibernation introduced with
this commit "020db9d3c1dc0"]
3. Merged couple of related patches to make the code more coherent and readable
4. Code refactoring
5. Sched clock fix when hibernating guest is under heavy CPU load
Note: Under very rare circumstances we see resume failures with KASLR enabled only
on xen instances.  We are roughly seeing 3% failures [>1000 runs] when testing with
various instance sizes and some workload running on each instance. I am currently
investigating the issue as to confirm if its a xen issue or kernel issue.
However, it should not hold back anyone from reviewing/accepting these patches.

Testing done:
All testing is done for multiple hibernation cycle for 5.4 kernel on EC2.

Testing How to:
---------------
Example:
Set up a file-backed swap space. Swap file size>=Total memory on the system
sudo dd if=/dev/zero of=/swap bs=$(( 1024 * 1024 )) count=4096 # 4096MiB
sudo chmod 600 /swap
sudo mkswap /swap
sudo swapon /swap

Update resume device/resume offset in grub if using swap file:
resume=/dev/xvda1 resume_offset=200704

Execute:
--------
sudo pm-hibernate
OR
echo disk > /sys/power/state && echo reboot > /sys/power/disk

Compute resume offset code:
"
#!/usr/bin/env python
import sys
import array
import fcntl

#swap file
f = open(sys.argv[1], 'r')
buf = array.array('L', [0])

#FIBMAP
ret = fcntl.ioctl(f.fileno(), 0x01, buf)
print buf[0]
"

Aleksei Besogonov (1):
  PM / hibernate: update the resume offset on SNAPSHOT_SET_SWAP_AREA

Anchal Agarwal (4):
  x86/xen: Introduce new function to map HYPERVISOR_shared_info on
    Resume
  genirq: Shutdown irq chips in suspend/resume during hibernation
  xen: Introduce wrapper for save/restore sched clock offset
  xen: Update sched clock offset to avoid system instability in
    hibernation

Munehisa Kamata (7):
  xen/manage: keep track of the on-going suspend mode
  xenbus: add freeze/thaw/restore callbacks support
  x86/xen: add system core suspend and resume callbacks
  xen-netfront: add callbacks for PM suspend and hibernation support
  xen-blkfront: add callbacks for PM suspend and hibernation
  xen/time: introduce xen_{save,restore}_steal_clock
  x86/xen: save and restore steal clock

 arch/x86/xen/enlighten_hvm.c      |   8 ++
 arch/x86/xen/suspend.c            |  72 ++++++++++++++++++
 arch/x86/xen/time.c               |  18 ++++-
 arch/x86/xen/xen-ops.h            |   3 +
 drivers/block/xen-blkfront.c      | 119 ++++++++++++++++++++++++++++--
 drivers/net/xen-netfront.c        |  98 +++++++++++++++++++++++-
 drivers/xen/events/events_base.c  |   1 +
 drivers/xen/manage.c              |  73 ++++++++++++++++++
 drivers/xen/time.c                |  29 +++++++-
 drivers/xen/xenbus/xenbus_probe.c |  99 ++++++++++++++++++++-----
 include/linux/irq.h               |   2 +
 include/xen/xen-ops.h             |   8 ++
 include/xen/xenbus.h              |   3 +
 kernel/irq/chip.c                 |   2 +-
 kernel/irq/internals.h            |   1 +
 kernel/irq/pm.c                   |  31 +++++---
 kernel/power/user.c               |   6 +-
 17 files changed, 533 insertions(+), 40 deletions(-)

-- 
2.24.1.AMZN


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Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

^ permalink raw reply	[flat|nested] 2+ messages in thread

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Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-12 22:34 [Xen-devel] [RFC PATCH v3 10/12] xen: Introduce wrapper for save/restore sched clock offset Anchal Agarwal
2020-02-14 23:21 [Xen-devel] [RFC RESEND PATCH v3 00/12] Enable PM hibernation on guest VMs Anchal Agarwal
2020-02-14 23:27 ` [Xen-devel] [RFC PATCH v3 10/12] xen: Introduce wrapper for save/restore sched clock offset Anchal Agarwal

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