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authorDavid Hildenbrand <david@redhat.com>2024-03-18 13:06:45 +0100
committerMichael S. Tsirkin <mst@redhat.com>2024-05-22 08:31:15 -0400
commite4544c550eb1857845bb7114bac53edd04dc078f (patch)
tree18789c06f5ed715b6ec00d8d2762927fe0f207ba /include/uapi
parent240a1853b4d2bce51e5cac9ba65cd646152ab6d6 (diff)
virtio-mem: support suspend+resume
With virtio-mem, primarily hibernation is problematic: as the machine shuts down, the virtio-mem device loses its state. Powering the machine back up is like losing a bunch of DIMMs. While there would be ways to add limited support, suspend+resume is more commonly used for VMs and "easier" to support cleanly. s2idle can be supported without any device dependencies. Similarly, one would expect suspend-to-ram (i.e., S3) to work out of the box. However, QEMU currently unplugs all device memory when resuming the VM, using a cold reset on the "wakeup" path. In order to support S3, we need a feature flag for the device to tell us if memory remains plugged when waking up. In the future, QEMU will implement this feature. So let's always support s2idle and support S3 with plugged memory only if the device indicates support. Block hibernation early using the PM notifier. Trying to hibernate now fails early: # echo disk > /sys/power/state [ 26.455369] PM: hibernation: hibernation entry [ 26.458271] virtio_mem virtio0: hibernation is not supported. [ 26.462498] PM: hibernation: hibernation exit -bash: echo: write error: Operation not permitted s2idle works even without the new feature bit: # echo s2idle > /sys/power/mem_sleep # echo mem > /sys/power/state [ 52.083725] PM: suspend entry (s2idle) [ 52.095950] Filesystems sync: 0.010 seconds [ 52.101493] Freezing user space processes [ 52.104213] Freezing user space processes completed (elapsed 0.001 seconds) [ 52.106520] OOM killer disabled. [ 52.107655] Freezing remaining freezable tasks [ 52.110880] Freezing remaining freezable tasks completed (elapsed 0.001 seconds) [ 52.113296] printk: Suspending console(s) (use no_console_suspend to debug) S3 does not work without the feature bit when memory is plugged: # echo deep > /sys/power/mem_sleep # echo mem > /sys/power/state [ 32.788281] PM: suspend entry (deep) [ 32.816630] Filesystems sync: 0.027 seconds [ 32.820029] Freezing user space processes [ 32.823870] Freezing user space processes completed (elapsed 0.001 seconds) [ 32.827756] OOM killer disabled. [ 32.829608] Freezing remaining freezable tasks [ 32.833842] Freezing remaining freezable tasks completed (elapsed 0.001 seconds) [ 32.837953] printk: Suspending console(s) (use no_console_suspend to debug) [ 32.916172] virtio_mem virtio0: suspend+resume with plugged memory is not supported [ 32.916181] virtio-pci 0000:00:02.0: PM: pci_pm_suspend(): virtio_pci_freeze+0x0/0x50 returns -1 [ 32.916197] virtio-pci 0000:00:02.0: PM: dpm_run_callback(): pci_pm_suspend+0x0/0x170 returns -1 [ 32.916210] virtio-pci 0000:00:02.0: PM: failed to suspend async: error -1 But S3 works with the new feature bit when memory is plugged (patched QEMU): # echo deep > /sys/power/mem_sleep # echo mem > /sys/power/state [ 33.983694] PM: suspend entry (deep) [ 34.009828] Filesystems sync: 0.024 seconds [ 34.013589] Freezing user space processes [ 34.016722] Freezing user space processes completed (elapsed 0.001 seconds) [ 34.019092] OOM killer disabled. [ 34.020291] Freezing remaining freezable tasks [ 34.023549] Freezing remaining freezable tasks completed (elapsed 0.001 seconds) [ 34.026090] printk: Suspending console(s) (use no_console_suspend to debug) Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Signed-off-by: David Hildenbrand <david@redhat.com> Message-Id: <20240318120645.105664-1-david@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'include/uapi')
-rw-r--r--include/uapi/linux/virtio_mem.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/uapi/linux/virtio_mem.h b/include/uapi/linux/virtio_mem.h
index e9122f1d0e0c..6e4b2cf6b7f1 100644
--- a/include/uapi/linux/virtio_mem.h
+++ b/include/uapi/linux/virtio_mem.h
@@ -90,6 +90,8 @@
#define VIRTIO_MEM_F_ACPI_PXM 0
/* unplugged memory must not be accessed */
#define VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE 1
+/* plugged memory will remain plugged when suspending+resuming */
+#define VIRTIO_MEM_F_PERSISTENT_SUSPEND 2
/* --- virtio-mem: guest -> host requests --- */