[RFC PATCH v5 0/4] virtio: add noirq system sleep PM callbacks for virtio-mmio

[RFC PATCH v5 0/4] virtio: add noirq system sleep PM callbacks for virtio-mmio

[Sungho Bae]

From: Sungho Bae <baver.bae@lge.com>

Hi all,

Some virtio-mmio based devices, such as virtio-clock or virtio-regulator,
must become operational before other devices have their regular PM restore
callbacks invoked, because those other devices depend on them.

Generally, PM framework provides the three phases (freeze, freeze_late,
freeze_noirq) for the system sleep sequence, and the corresponding resume
phases. But, virtio core only supports the normal freeze/restore phase,
so virtio drivers have no way to participate in the noirq phase, which runs
with IRQs disabled and is guaranteed to run before any normal-phase restore
callbacks.

This series adds the infrastructure and the virtio-mmio transport
wiring so that virtio drivers can implement freeze_noirq/restore_noirq
callbacks.

Design overview
===============

The noirq phase runs with device IRQ handlers disabled and must avoid
sleepable operations. The main constraints addressed are:

 - might_sleep() in virtio_add_status() and virtio_features_ok().
 - virtio_synchronize_cbs() in virtio_reset_device() (IRQs are already
   quiesced).
 - spin_lock_irq() in virtio_config_core_enable() (not safe to call
   with interrupts already disabled).
 - Memory allocation during vq setup (virtqueue_reinit_vring() reuses
   existing buffers instead).

The series provides noirq-safe variants for each of these, plus a new
config_ops->reset_vqs() callback that lets the transport reprogram
queue registers without freeing/reallocating vring memory.

Not all transports can safely perform these operations in the noirq phase.
Transports like virtio-ccw issue channel commands and wait for a completion
interrupt, which will never arrive while device interrupts are masked at
the interrupt controller. A new boolean field config_ops->noirq_safe marks
transports that implement reset/status operations via simple MMIO
reads/writes and are therefore safe to use in noirq context. The noirq
helpers assert this flag at runtime, and virtio_device_freeze_noirq()
enforces it at freeze time, returning -EOPNOTSUPP early to prevent
a deadlock on resume.

When a driver implements restore_noirq, the device bring-up (reset ->
ACKNOWLEDGE -> DRIVER -> finalize_features -> FEATURES_OK) happens in
the noirq phase. The subsequent normal-phase virtio_device_restore()
detects this and skips the redundant re-initialization.

Patch breakdown
===============

Patch 1 is a preparatory refactoring with no functional change.
Patches 2-3 add the core infrastructure. Patch 4 wires it up for
virtio-mmio.

 1. virtio: separate PM restore and reset_done paths

    Splits virtio_device_restore_priv() into independent
    virtio_device_restore() and virtio_device_reset_done() paths,
    using a shared virtio_device_reinit() helper. This is a pure
    refactoring to make the restore path independently extensible
    without complicating the boolean dispatch.

 2. virtio_ring: export virtqueue_reinit_vring() for noirq restore

    Adds virtqueue_reinit_vring(), an exported wrapper that resets
    vring indices and descriptor state in place without any memory
    allocation, making it safe to call from noirq context. Also
    resets IN_ORDER-specific state (free_head, batch_last.id) in
    virtqueue_init() to keep the ring consistent after reinit, and
    adds runtime WARN_ON checks for unexpected in-flight descriptor
    state and split-ring index consistency.

 3. virtio: add noirq system sleep PM infrastructure

    Adds noirq-safe helpers (virtio_add_status_noirq,
    virtio_features_ok_noirq, virtio_reset_device_noirq,
    virtio_config_core_enable_noirq, virtio_device_ready_noirq) and
    the freeze_noirq/restore_noirq driver callbacks plus the
    config_ops->reset_vqs() transport hook. Introduces
    config_ops->noirq_safe to mark transports whose reset/status
    operations are safe in noirq context (e.g. simple MMIO), and
    enforces early -EOPNOTSUPP in virtio_device_freeze_noirq() when
    the transport does not meet noirq requirements. Modifies
    virtio_device_restore() to skip bring-up when restore_noirq
    already ran.

 4. virtio-mmio: wire up noirq system sleep PM callbacks

    Implements vm_reset_vqs() which iterates existing virtqueues,
    reinitializes the vring state via virtqueue_reinit_vring(), and
    reprograms the MMIO queue registers. Adds
    virtio_mmio_freeze_noirq/virtio_mmio_restore_noirq and registers
    them via SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(). Sets .noirq_safe = true
    in virtio_mmio_config_ops to declare that MMIO-based status and
    reset operations are safe during the noirq PM phase.

Testing
=======

Build-tested with arm64 cross-compilation.
(make ARCH=arm64 M=drivers/virtio)

Runtime-tested on an internal virtio-mmio platform with virtio-clock,
confirming that the clock device works well before other devices' normal
restore() callbacks run.

Changes
=======

v5:
  virtio: add noirq system sleep PM infrastructure
   - Preserve FAILED across restore_noirq() failure by recording the
     failure in dev->failed before falling back to the normal restore path.
   - Document the restore/restore_noirq fallback contract more clearly,
     especially for drivers that preserve virtqueues across suspend.

v4:
  virtio_ring: export virtqueue_reinit_vring() for noirq restore
   - Reinit safety was tightened by resetting IN_ORDER-specific state.
   - Added extra split-ring consistency WARN_ON checks.
   - Clarified caller preconditions for noirq-safe vring reinit.

  virtio: add noirq system sleep PM infrastructure
   - Added config_ops->noirq_safe to explicitly mark transports that are
     safe in noirq PM phase.
   - Enforced early -EOPNOTSUPP checks in freeze_noirq for unsupported
     transport combinations (noirq_safe/reset_vqs requirements).
   - Added defensive runtime guards/warnings in noirq helper and restore
     paths.
   - Discussed the freeze-before-freeze_noirq abort scenario raised in
     review and concluded that the fallback restore path is intentionally
     handled by regular restore after core reinit/reset, so reset_vqs is
     kept limited to the noirq restore flow.

  virtio-mmio: wire up noirq system sleep PM callbacks
   - Marked virtio-mmio transport as noirq-capable by setting .noirq_safe
     in virtio_mmio_config_ops.

v3:
  virtio: separate PM restore and reset_done paths
   - Refined restore flow to explicitly handle the no-driver case after
     reinit, improving clarity and avoiding unnecessary driver-path
     assumptions.

  virtio_ring: export virtqueue_reinit_vring() for noirq restore
   - Hardened virtqueue_reinit_vring() with stronger safety notes and
     a runtime WARN_ON check to catch reinit with unexpected free-list
     state.

  virtio: add noirq system sleep PM infrastructure
   - Added explicit noirq restore completion tracking noirq_restore_done
     and updated PM sequencing to use it, plus early freeze_noirq
     validation for missing reset_vqs support.

  virtio-mmio: wire up noirq system sleep PM callbacks
   - Updated virtio-mmio restore path to skip legacy GUEST_PAGE_SIZE
     rewrite when noirq restore already completed.

v2:
  virtio-mmio: wire up noirq system sleep PM callbacks
   - The code that was duplicated in vm_setup_vq() and vm_reset_vqs() has
     been moved to vm_active_vq() function.


Sungho Bae (4):
  virtio: separate PM restore and reset_done paths
  virtio_ring: export virtqueue_reinit_vring() for noirq restore
  virtio: add noirq system sleep PM infrastructure
  virtio-mmio: wire up noirq system sleep PM callbacks

 drivers/virtio/virtio.c       | 298 +++++++++++++++++++++++++++++++---
 drivers/virtio/virtio_mmio.c  | 134 ++++++++++-----
 drivers/virtio/virtio_ring.c  |  51 ++++++
 include/linux/virtio.h        |  17 ++
 include/linux/virtio_config.h |  39 +++++
 include/linux/virtio_ring.h   |   3 +
 6 files changed, 476 insertions(+), 66 deletions(-)

-- 
2.43.0

[RFC PATCH v5 1/4] virtio: separate PM restore and reset_done paths

[Sungho Bae]

From: Sungho Bae <baver.bae@lge.com>

Refactor virtio_device_restore_priv() by extracting the common device
re-initialization sequence into virtio_device_reinit(). This helper
performs the full bring-up sequence: reset, status acknowledgment,
feature finalization, and feature negotiation.

virtio_device_restore() and virtio_device_reset_done() now each call
virtio_device_reinit() directly instead of going through a boolean-
dispatched wrapper. This makes each path independently readable and
extensible without further complicating the dispatch logic.

A follow-up series will add noirq PM callbacks that only affect the
restore path; having the two paths separated avoids adding more
conditionals to a shared function.

No functional change.

Signed-off-by: Sungho Bae <baver.bae@lge.com>
---
 drivers/virtio/virtio.c | 81 +++++++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 31 deletions(-)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 5bdc6b82b30b..98f1875f8df1 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -588,7 +588,7 @@ void unregister_virtio_device(struct virtio_device *dev)
 }
 EXPORT_SYMBOL_GPL(unregister_virtio_device);
 
-static int virtio_device_restore_priv(struct virtio_device *dev, bool restore)
+static int virtio_device_reinit(struct virtio_device *dev)
 {
 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
 	int ret;
@@ -613,35 +613,9 @@ static int virtio_device_restore_priv(struct virtio_device *dev, bool restore)
 
 	ret = dev->config->finalize_features(dev);
 	if (ret)
-		goto err;
-
-	ret = virtio_features_ok(dev);
-	if (ret)
-		goto err;
-
-	if (restore) {
-		if (drv->restore) {
-			ret = drv->restore(dev);
-			if (ret)
-				goto err;
-		}
-	} else {
-		ret = drv->reset_done(dev);
-		if (ret)
-			goto err;
-	}
-
-	/* If restore didn't do it, mark device DRIVER_OK ourselves. */
-	if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
-		virtio_device_ready(dev);
-
-	virtio_config_core_enable(dev);
-
-	return 0;
+		return ret;
 
-err:
-	virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
-	return ret;
+	return virtio_features_ok(dev);
 }
 
 #ifdef CONFIG_PM_SLEEP
@@ -668,7 +642,33 @@ EXPORT_SYMBOL_GPL(virtio_device_freeze);
 
 int virtio_device_restore(struct virtio_device *dev)
 {
-	return virtio_device_restore_priv(dev, true);
+	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+	int ret;
+
+	ret = virtio_device_reinit(dev);
+	if (ret)
+		goto err;
+
+	if (!drv)
+		return 0;
+
+	if (drv->restore) {
+		ret = drv->restore(dev);
+		if (ret)
+			goto err;
+	}
+
+	/* If restore didn't do it, mark device DRIVER_OK ourselves. */
+	if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
+		virtio_device_ready(dev);
+
+	virtio_config_core_enable(dev);
+
+	return 0;
+
+err:
+	virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(virtio_device_restore);
 #endif
@@ -698,11 +698,30 @@ EXPORT_SYMBOL_GPL(virtio_device_reset_prepare);
 int virtio_device_reset_done(struct virtio_device *dev)
 {
 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+	int ret;
 
 	if (!drv || !drv->reset_done)
 		return -EOPNOTSUPP;
 
-	return virtio_device_restore_priv(dev, false);
+	ret = virtio_device_reinit(dev);
+	if (ret)
+		goto err;
+
+	ret = drv->reset_done(dev);
+	if (ret)
+		goto err;
+
+	/* If reset_done didn't do it, mark device DRIVER_OK ourselves. */
+	if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
+		virtio_device_ready(dev);
+
+	virtio_config_core_enable(dev);
+
+	return 0;
+
+err:
+	virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(virtio_device_reset_done);
 
-- 
2.43.0

[RFC PATCH v5 2/4] virtio_ring: export virtqueue_reinit_vring() for noirq restore

[Sungho Bae]

From: Sungho Bae <baver.bae@lge.com>

After a device reset in noirq context the existing vrings must be
re-initialized without any memory allocation, because GFP_KERNEL is
not available.

The internal helpers virtqueue_reset_split() and
virtqueue_reset_packed() already reset vring indices and descriptor
state in place.  Add a thin exported wrapper, virtqueue_reinit_vring(),
that dispatches to the appropriate helper based on the ring layout.

This will be used by a subsequent patch that adds noirq system-sleep
PM callbacks for virtio-mmio.

Signed-off-by: Sungho Bae <baver.bae@lge.com>
---
 drivers/virtio/virtio_ring.c | 51 ++++++++++++++++++++++++++++++++++++
 include/linux/virtio_ring.h  |  3 +++
 2 files changed, 54 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index fbca7ce1c6bf..6631c30cb706 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -506,6 +506,15 @@ static void virtqueue_init(struct vring_virtqueue *vq, u32 num)
 	vq->event_triggered = false;
 	vq->num_added = 0;
 
+	/*
+	 * Keep IN_ORDER state aligned with a freshly initialized/reset queue.
+	 * For packed IN_ORDER, free_head is unused but harmlessly reset.
+	 */
+	if (virtqueue_is_in_order(vq)) {
+		vq->free_head = 0;
+		vq->batch_last.id = UINT_MAX;
+	}
+
 #ifdef DEBUG
 	vq->in_use = false;
 	vq->last_add_time_valid = false;
@@ -3936,5 +3945,47 @@ void virtqueue_map_sync_single_range_for_device(const struct virtqueue *_vq,
 }
 EXPORT_SYMBOL_GPL(virtqueue_map_sync_single_range_for_device);
 
+/**
+ * virtqueue_reinit_vring - reinitialize vring state without reallocation
+ * @_vq: the virtqueue
+ *
+ * Reset the avail/used indices and descriptor state of an existing
+ * virtqueue so it can be reused after a device reset.  No memory is
+ * allocated or freed, making this safe for use in noirq context.
+ *
+ * Preconditions for callers:
+ * 1) The vq must be fully quiesced (no concurrent add/get/kick/IRQ callback).
+ * 2) Transport/device side must already have stopped/reset this queue.
+ * 3) All in-flight buffers must already be completed or detached.
+ *
+ * If called with outstanding descriptors, free-list state can be corrupted:
+ * num_free is restored to full capacity while desc_extra next-chain/free_head
+ * may still represent a partially consumed list.
+ */
+void virtqueue_reinit_vring(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+	unsigned int num = virtqueue_is_packed(vq) ?
+		vq->packed.vring.num : vq->split.vring.num;
+
+	/* All in-flight descriptors must be completed or detached */
+	WARN_ON(vq->vq.num_free != num);
+
+	if (virtqueue_is_packed(vq)) {
+		virtqueue_reset_packed(vq);
+	} else {
+		/*
+		 * Split queue shadow index should match the visible avail
+		 * index when the queue is fully quiesced.
+		 */
+		WARN_ON(vq->split.avail_idx_shadow !=
+			virtio16_to_cpu(vq->vq.vdev,
+					vq->split.vring.avail->idx));
+
+		virtqueue_reset_split(vq);
+	}
+}
+EXPORT_SYMBOL_GPL(virtqueue_reinit_vring);
+
 MODULE_DESCRIPTION("Virtio ring implementation");
 MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index c97a12c1cda3..26c7c9d0a151 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -118,6 +118,9 @@ void vring_del_virtqueue(struct virtqueue *vq);
 /* Filter out transport-specific feature bits. */
 void vring_transport_features(struct virtio_device *vdev);
 
+/* Reinitialize a virtqueue without reallocation (safe in noirq context) */
+void virtqueue_reinit_vring(struct virtqueue *_vq);
+
 irqreturn_t vring_interrupt(int irq, void *_vq);
 
 u32 vring_notification_data(struct virtqueue *_vq);
-- 
2.43.0

[RFC PATCH v5 3/4] virtio: add noirq system sleep PM infrastructure

[Sungho Bae]

From: Sungho Bae <baver.bae@lge.com>

Some virtio-mmio devices, such as virtio-clock or virtio-regulator,
must become operational before the regular PM restore callback runs
because other devices may depend on them.

Add the core infrastructure needed to support noirq system-sleep PM
callbacks for virtio transports:

 - virtio_add_status_noirq(): status helper without might_sleep().
 - virtio_features_ok_noirq(): feature negotiation without might_sleep().
 - virtio_reset_device_noirq(): device reset that skips
   virtio_synchronize_cbs() (IRQ handlers are already quiesced in the
   noirq phase).
 - virtio_device_reinit_noirq(): full noirq bring-up sequence using the
   above helpers.
 - virtio_config_core_enable_noirq(): config enable with irqsave
   locking.
 - virtio_device_ready_noirq(): marks DRIVER_OK without
   virtio_synchronize_cbs().

Not all transports can safely call reset, get_status, set_status, or
finalize_features during the noirq phase: transports like virtio-ccw
issue channel commands and wait for a completion interrupt, which will
never be delivered because device interrupts are masked at the interrupt
controller during noirq suspend/resume.  To address this, introduce a
boolean field noirq_safe in struct virtio_config_ops.  Transports that
implement the above operations via simple MMIO reads/writes (e.g.
virtio-mmio) set this flag; all others leave it at the default false.

The noirq helpers assert noirq_safe via WARN_ON at runtime.
virtio_device_freeze_noirq() enforces the contract at freeze time,
returning -EOPNOTSUPP early if the driver provides restore_noirq but
the transport does not meet the requirements, to prevent a deadlock on
resume. virtio_device_restore_noirq() performs a second check as a
safety net in case freeze_noirq was not called.

Add freeze_noirq/restore_noirq callbacks to struct virtio_driver and
provide matching helper wrappers in the virtio core:

 - virtio_device_freeze_noirq(): validates noirq_safe and reset_vqs
   requirements, then forwards to drv->freeze_noirq().
 - virtio_device_restore_noirq(): guards against unsafe transports,
   runs the noirq bring-up sequence, resets existing vrings via the
   new config_ops->reset_vqs() hook, then calls drv->restore_noirq().

Modify virtio_device_restore() so that when a driver provides
restore_noirq, the normal-phase restore skips the re-initialization
that was already done in the noirq phase.

Signed-off-by: Sungho Bae <baver.bae@lge.com>
---
 drivers/virtio/virtio.c       | 239 +++++++++++++++++++++++++++++++++-
 include/linux/virtio.h        |  17 +++
 include/linux/virtio_config.h |  39 ++++++
 3 files changed, 289 insertions(+), 6 deletions(-)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 98f1875f8df1..b1d2cba7d59a 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -193,6 +193,17 @@ static void virtio_config_core_enable(struct virtio_device *dev)
 	spin_unlock_irq(&dev->config_lock);
 }
 
+static void virtio_config_core_enable_noirq(struct virtio_device *dev)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->config_lock, flags);
+	dev->config_core_enabled = true;
+	if (dev->config_change_pending)
+		__virtio_config_changed(dev);
+	spin_unlock_irqrestore(&dev->config_lock, flags);
+}
+
 void virtio_add_status(struct virtio_device *dev, unsigned int status)
 {
 	might_sleep();
@@ -200,6 +211,21 @@ void virtio_add_status(struct virtio_device *dev, unsigned int status)
 }
 EXPORT_SYMBOL_GPL(virtio_add_status);
 
+/*
+ * Same as virtio_add_status() but without the might_sleep() assertion,
+ * so it is safe to call from noirq context.
+ *
+ * Requires the transport to have set config_ops->noirq_safe, which declares
+ * that reset, get_status, and set_status do not wait for a completion
+ * interrupt and are therefore safe during the noirq PM phase.
+ */
+void virtio_add_status_noirq(struct virtio_device *dev, unsigned int status)
+{
+	WARN_ON(!dev->config->noirq_safe);
+	dev->config->set_status(dev, dev->config->get_status(dev) | status);
+}
+EXPORT_SYMBOL_GPL(virtio_add_status_noirq);
+
 /* Do some validation, then set FEATURES_OK */
 static int virtio_features_ok(struct virtio_device *dev)
 {
@@ -234,6 +260,38 @@ static int virtio_features_ok(struct virtio_device *dev)
 	return 0;
 }
 
+/* noirq-safe variant: no might_sleep(), uses virtio_add_status_noirq() */
+static int virtio_features_ok_noirq(struct virtio_device *dev)
+{
+	unsigned int status;
+
+	if (virtio_check_mem_acc_cb(dev)) {
+		if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
+			dev_warn(&dev->dev,
+				 "device must provide VIRTIO_F_VERSION_1\n");
+			return -ENODEV;
+		}
+
+		if (!virtio_has_feature(dev, VIRTIO_F_ACCESS_PLATFORM)) {
+			dev_warn(&dev->dev,
+				 "device must provide VIRTIO_F_ACCESS_PLATFORM\n");
+			return -ENODEV;
+		}
+	}
+
+	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
+		return 0;
+
+	virtio_add_status_noirq(dev, VIRTIO_CONFIG_S_FEATURES_OK);
+	status = dev->config->get_status(dev);
+	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
+		dev_err(&dev->dev, "virtio: device refuses features: %x\n",
+			status);
+		return -ENODEV;
+	}
+	return 0;
+}
+
 /**
  * virtio_reset_device - quiesce device for removal
  * @dev: the device to reset
@@ -267,6 +325,28 @@ void virtio_reset_device(struct virtio_device *dev)
 }
 EXPORT_SYMBOL_GPL(virtio_reset_device);
 
+/**
+ * virtio_reset_device_noirq - noirq-safe variant of virtio_reset_device()
+ * @dev: the device to reset
+ *
+ * Requires the transport to have set config_ops->noirq_safe.
+ */
+void virtio_reset_device_noirq(struct virtio_device *dev)
+{
+	WARN_ON(!dev->config->noirq_safe);
+
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+	/*
+	 * The noirq stage runs with device IRQ handlers disabled, so
+	 * virtio_synchronize_cbs() must not be called here.
+	 */
+	virtio_break_device(dev);
+#endif
+
+	dev->config->reset(dev);
+}
+EXPORT_SYMBOL_GPL(virtio_reset_device_noirq);
+
 static int virtio_dev_probe(struct device *_d)
 {
 	int err, i;
@@ -539,6 +619,7 @@ int register_virtio_device(struct virtio_device *dev)
 	dev->config_driver_disabled = false;
 	dev->config_core_enabled = false;
 	dev->config_change_pending = false;
+	dev->noirq_restore_done = false;
 
 	INIT_LIST_HEAD(&dev->vqs);
 	spin_lock_init(&dev->vqs_list_lock);
@@ -618,6 +699,47 @@ static int virtio_device_reinit(struct virtio_device *dev)
 	return virtio_features_ok(dev);
 }
 
+/*
+ * noirq-safe variant of virtio_device_reinit().
+ *
+ * Requires the transport to declare config_ops->noirq_safe, which means
+ * reset, get_status, set_status, and finalize_features are safe to call
+ * during the noirq PM phase.
+ */
+static int virtio_device_reinit_noirq(struct virtio_device *dev)
+{
+	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+	int ret;
+
+	/*
+	 * We always start by resetting the device, in case a previous
+	 * driver messed it up.
+	 */
+	virtio_reset_device_noirq(dev);
+
+	/* Acknowledge that we've seen the device. */
+	virtio_add_status_noirq(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
+
+	/*
+	 * Maybe driver failed before freeze.
+	 * Restore the failed status, for debugging.
+	 */
+	if (dev->failed)
+		virtio_add_status_noirq(dev, VIRTIO_CONFIG_S_FAILED);
+
+	if (!drv)
+		return 0;
+
+	/* We have a driver! */
+	virtio_add_status_noirq(dev, VIRTIO_CONFIG_S_DRIVER);
+
+	ret = dev->config->finalize_features(dev);
+	if (ret)
+		return ret;
+
+	return virtio_features_ok_noirq(dev);
+}
+
 #ifdef CONFIG_PM_SLEEP
 int virtio_device_freeze(struct virtio_device *dev)
 {
@@ -627,6 +749,7 @@ int virtio_device_freeze(struct virtio_device *dev)
 	virtio_config_core_disable(dev);
 
 	dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
+	dev->noirq_restore_done = false;
 
 	if (drv && drv->freeze) {
 		ret = drv->freeze(dev);
@@ -645,12 +768,22 @@ int virtio_device_restore(struct virtio_device *dev)
 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
 	int ret;
 
-	ret = virtio_device_reinit(dev);
-	if (ret)
-		goto err;
-
-	if (!drv)
-		return 0;
+	/*
+	 * If this device was already brought up in the noirq phase,
+	 * skip the re-initialization here.
+	 *
+	 * Note: this normal restore path does not call reset_vqs().
+	 * Drivers that implement restore_noirq and preserve virtqueues
+	 * must make queue/device state consistent in ->restore() when
+	 * noirq restore did not complete.
+	 */
+	if (!drv || !dev->noirq_restore_done) {
+		ret = virtio_device_reinit(dev);
+		if (ret)
+			goto err;
+		if (!drv)
+			return 0;
+	}
 
 	if (drv->restore) {
 		ret = drv->restore(dev);
@@ -671,6 +804,100 @@ int virtio_device_restore(struct virtio_device *dev)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(virtio_device_restore);
+
+int virtio_device_freeze_noirq(struct virtio_device *dev)
+{
+	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+
+	if (!drv)
+		return 0;
+
+	/*
+	 * restore_noirq requires that the transport's config ops
+	 * (reset, get_status, set_status) are safe to call during the noirq
+	 * PM phase. Catch the mismatch early at freeze time so the PM core
+	 * can abort cleanly rather than deadlocking on resume.
+	 */
+	if (drv->restore_noirq && !dev->config->noirq_safe) {
+		dev_warn(&dev->dev,
+			 "transport does not support noirq PM\n");
+		return -EOPNOTSUPP;
+	}
+
+	/*
+	 * If the driver provides restore_noirq and has active vqs,
+	 * the transport must support reset_vqs to restore them.
+	 * Fail here so the PM core can abort the transition gracefully,
+	 * rather than hitting -EOPNOTSUPP on resume.
+	 */
+	if (drv->restore_noirq && !list_empty(&dev->vqs) &&
+	    !dev->config->reset_vqs) {
+		dev_warn(&dev->dev,
+			 "transport does not support noirq PM restore with active vqs (missing reset_vqs)\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (drv->freeze_noirq)
+		return drv->freeze_noirq(dev);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(virtio_device_freeze_noirq);
+
+int virtio_device_restore_noirq(struct virtio_device *dev)
+{
+	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+	int ret;
+
+	if (!drv || !drv->restore_noirq)
+		return 0;
+
+	/*
+	 * All transport ops called below (reset, get_status, set_status) must
+	 * be noirq-safe.  Return early if not - this should normally have
+	 * been caught at freeze_noirq time.
+	 */
+	if (!dev->config->noirq_safe) {
+		dev_warn(&dev->dev,
+			 "transport does not support noirq PM; skipping restore\n");
+		return -EOPNOTSUPP;
+	}
+
+	ret = virtio_device_reinit_noirq(dev);
+	if (ret)
+		goto err;
+
+	if (!list_empty(&dev->vqs)) {
+		if (!dev->config->reset_vqs) {
+			ret = -EOPNOTSUPP;
+			goto err;
+		}
+
+		ret = dev->config->reset_vqs(dev);
+		if (ret)
+			goto err;
+	}
+
+	ret = drv->restore_noirq(dev);
+	if (ret)
+		goto err;
+
+	/* Mark that noirq restore has completed. */
+	dev->noirq_restore_done = true;
+
+	/* If restore_noirq set DRIVER_OK, enable config now. */
+	if (dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK)
+		virtio_config_core_enable_noirq(dev);
+
+	return 0;
+
+err:
+	/* Record that noirq restore failed so FAILED status persists across reset/reinit. */
+	dev->failed = true;
+	virtio_add_status_noirq(dev, VIRTIO_CONFIG_S_FAILED);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(virtio_device_restore_noirq);
 #endif
 
 int virtio_device_reset_prepare(struct virtio_device *dev)
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 3bbc4cb6a672..c4f85f1ebffa 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -151,6 +151,7 @@ struct virtio_admin_cmd {
  * @config_driver_disabled: configuration change reporting disabled by
  *                          a driver
  * @config_change_pending: configuration change reported while disabled
+ * @noirq_restore_done: set if the noirq restore phase completed successfully
  * @config_lock: protects configuration change reporting
  * @vqs_list_lock: protects @vqs.
  * @dev: underlying device.
@@ -171,6 +172,7 @@ struct virtio_device {
 	bool config_core_enabled;
 	bool config_driver_disabled;
 	bool config_change_pending;
+	bool noirq_restore_done;
 	spinlock_t config_lock;
 	spinlock_t vqs_list_lock;
 	struct device dev;
@@ -209,8 +211,12 @@ void virtio_config_driver_enable(struct virtio_device *dev);
 #ifdef CONFIG_PM_SLEEP
 int virtio_device_freeze(struct virtio_device *dev);
 int virtio_device_restore(struct virtio_device *dev);
+int virtio_device_freeze_noirq(struct virtio_device *dev);
+int virtio_device_restore_noirq(struct virtio_device *dev);
 #endif
 void virtio_reset_device(struct virtio_device *dev);
+void virtio_reset_device_noirq(struct virtio_device *dev);
+void virtio_add_status_noirq(struct virtio_device *dev, unsigned int status);
 int virtio_device_reset_prepare(struct virtio_device *dev);
 int virtio_device_reset_done(struct virtio_device *dev);
 
@@ -237,6 +243,15 @@ size_t virtio_max_dma_size(const struct virtio_device *vdev);
  *    changes; may be called in interrupt context.
  * @freeze: optional function to call during suspend/hibernation.
  * @restore: optional function to call on resume.
+ *    If noirq resume was skipped or failed, core may have reset the device
+ *    before calling this callback. Drivers that preserve virtqueues for
+ *    @restore_noirq must make queue/device state consistent here before
+ *    returning success.
+ * @freeze_noirq: optional function to call during noirq suspend/hibernation.
+ * @restore_noirq: optional function to call on noirq resume.
+ *    If this callback fails, PM core may fall back to @restore. The fallback
+ *    normal resume path does not implicitly perform transport queue reset for
+ *    preserved virtqueues; drivers must handle that in @restore if needed.
  * @reset_prepare: optional function to call when a transport specific reset
  *    occurs.
  * @reset_done: optional function to call after transport specific reset
@@ -258,6 +273,8 @@ struct virtio_driver {
 	void (*config_changed)(struct virtio_device *dev);
 	int (*freeze)(struct virtio_device *dev);
 	int (*restore)(struct virtio_device *dev);
+	int (*freeze_noirq)(struct virtio_device *dev);
+	int (*restore_noirq)(struct virtio_device *dev);
 	int (*reset_prepare)(struct virtio_device *dev);
 	int (*reset_done)(struct virtio_device *dev);
 	void (*shutdown)(struct virtio_device *dev);
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 69f84ea85d71..81af2ad6a7c3 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -70,6 +70,9 @@ struct virtqueue_info {
  *	vqs_info: array of virtqueue info structures
  *	Returns 0 on success or error status
  * @del_vqs: free virtqueues found by find_vqs().
+ * @reset_vqs: reinitialize existing virtqueues without allocating or
+ *	freeing them (optional).  Used during noirq restore.
+ *	Returns 0 on success or error status.
  * @synchronize_cbs: synchronize with the virtqueue callbacks (optional)
  *      The function guarantees that all memory operations on the
  *      queue before it are visible to the vring_interrupt() that is
@@ -108,6 +111,14 @@ struct virtqueue_info {
  *	Returns 0 on success or error status
  *	If disable_vq_and_reset is set, then enable_vq_after_reset must also be
  *	set.
+ * @noirq_safe: set to true if @reset, @get_status, @set_status, and
+ *	@finalize_features are safe to call during the noirq phase of system
+ *	suspend/resume.  Transports that implement these operations via simple
+ *	MMIO reads/writes (e.g. virtio-mmio) can set this flag.  Transports
+ *	that issue channel commands and wait for a completion interrupt (e.g.
+ *	virtio-ccw) must NOT set it, because device interrupts are masked at
+ *	the interrupt controller during the noirq phase, which would cause the
+ *	wait to hang.
  */
 struct virtio_config_ops {
 	void (*get)(struct virtio_device *vdev, unsigned offset,
@@ -123,6 +134,7 @@ struct virtio_config_ops {
 			struct virtqueue_info vqs_info[],
 			struct irq_affinity *desc);
 	void (*del_vqs)(struct virtio_device *);
+	int (*reset_vqs)(struct virtio_device *vdev);
 	void (*synchronize_cbs)(struct virtio_device *);
 	u64 (*get_features)(struct virtio_device *vdev);
 	void (*get_extended_features)(struct virtio_device *vdev,
@@ -137,6 +149,7 @@ struct virtio_config_ops {
 			       struct virtio_shm_region *region, u8 id);
 	int (*disable_vq_and_reset)(struct virtqueue *vq);
 	int (*enable_vq_after_reset)(struct virtqueue *vq);
+	bool noirq_safe;
 };
 
 /**
@@ -371,6 +384,32 @@ void virtio_device_ready(struct virtio_device *dev)
 	dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
 }
 
+/**
+ * virtio_device_ready_noirq - noirq-safe variant of virtio_device_ready()
+ * @dev: the virtio device
+ *
+ * Requires the transport to have set config_ops->noirq_safe, which declares
+ * that get_status and set_status do not wait for a completion interrupt.
+ */
+static inline
+void virtio_device_ready_noirq(struct virtio_device *dev)
+{
+	unsigned int status = dev->config->get_status(dev);
+
+	WARN_ON(!dev->config->noirq_safe);
+	WARN_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
+
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+	/*
+	 * The noirq stage runs with device IRQ handlers disabled, so
+	 * virtio_synchronize_cbs() must not be called here.
+	 */
+	__virtio_unbreak_device(dev);
+#endif
+
+	dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
+}
+
 static inline
 const char *virtio_bus_name(struct virtio_device *vdev)
 {
-- 
2.43.0

[RFC PATCH v5 4/4] virtio-mmio: wire up noirq system sleep PM callbacks

[Sungho Bae]

From: Sungho Bae <baver.bae@lge.com>

Add noirq system-sleep PM support to the virtio-mmio transport.

This change wires noirq freeze/restore callbacks into virtio-mmio and
hooks queue reset/reactivation into the transport config ops so virtqueues
can be reinitialized and reused across suspend/resume.

For legacy (v1) devices, keep GUEST_PAGE_SIZE programming aligned with the
noirq restore path while avoiding duplicate programming in normal restore.

This enables virtio-mmio based devices to participate safely in the noirq
PM phase, which is required for early-restore users.

Signed-off-by: Sungho Bae <baver.bae@lge.com>
---
 drivers/virtio/virtio_mmio.c | 134 ++++++++++++++++++++++++-----------
 1 file changed, 94 insertions(+), 40 deletions(-)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 595c2274fbb5..1cd262f9f8b6 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -336,6 +336,75 @@ static void vm_del_vqs(struct virtio_device *vdev)
 	free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
 }
 
+static int vm_active_vq(struct virtio_device *vdev, struct virtqueue *vq)
+{
+	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
+	int q_num = virtqueue_get_vring_size(vq);
+
+	writel(q_num, vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
+	if (vm_dev->version == 1) {
+		u64 q_pfn = virtqueue_get_desc_addr(vq) >> PAGE_SHIFT;
+
+		/*
+		 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something
+		 * that doesn't fit in 32bit, fail the setup rather than
+		 * pretending to be successful.
+		 */
+		if (q_pfn >> 32) {
+			dev_err(&vdev->dev,
+				"platform bug: legacy virtio-mmio must not be used with RAM above 0x%llxGB\n",
+				0x1ULL << (32 + PAGE_SHIFT - 30));
+			return -E2BIG;
+		}
+
+		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
+		writel(q_pfn, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+	} else {
+		u64 addr;
+
+		addr = virtqueue_get_desc_addr(vq);
+		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
+		writel((u32)(addr >> 32),
+				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
+
+		addr = virtqueue_get_avail_addr(vq);
+		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
+		writel((u32)(addr >> 32),
+				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
+
+		addr = virtqueue_get_used_addr(vq);
+		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
+		writel((u32)(addr >> 32),
+				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
+
+		writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
+	}
+
+	return 0;
+}
+
+static int vm_reset_vqs(struct virtio_device *vdev)
+{
+	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
+	struct virtqueue *vq;
+	int err;
+
+	virtio_device_for_each_vq(vdev, vq) {
+		/* Re-initialize vring state */
+		virtqueue_reinit_vring(vq);
+
+		/* Select the queue we're interested in */
+		writel(vq->index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
+
+		/* Activate the queue */
+		err = vm_active_vq(vdev, vq);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
 static void vm_synchronize_cbs(struct virtio_device *vdev)
 {
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
@@ -388,45 +457,9 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in
 	vq->num_max = num;
 
 	/* Activate the queue */
-	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
-	if (vm_dev->version == 1) {
-		u64 q_pfn = virtqueue_get_desc_addr(vq) >> PAGE_SHIFT;
-
-		/*
-		 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something
-		 * that doesn't fit in 32bit, fail the setup rather than
-		 * pretending to be successful.
-		 */
-		if (q_pfn >> 32) {
-			dev_err(&vdev->dev,
-				"platform bug: legacy virtio-mmio must not be used with RAM above 0x%llxGB\n",
-				0x1ULL << (32 + PAGE_SHIFT - 30));
-			err = -E2BIG;
-			goto error_bad_pfn;
-		}
-
-		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
-		writel(q_pfn, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
-	} else {
-		u64 addr;
-
-		addr = virtqueue_get_desc_addr(vq);
-		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
-		writel((u32)(addr >> 32),
-				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
-
-		addr = virtqueue_get_avail_addr(vq);
-		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
-		writel((u32)(addr >> 32),
-				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
-
-		addr = virtqueue_get_used_addr(vq);
-		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
-		writel((u32)(addr >> 32),
-				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
-
-		writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
-	}
+	err = vm_active_vq(vdev, vq);
+	if (err < 0)
+		goto error_bad_pfn;
 
 	return vq;
 
@@ -528,11 +561,13 @@ static const struct virtio_config_ops virtio_mmio_config_ops = {
 	.reset		= vm_reset,
 	.find_vqs	= vm_find_vqs,
 	.del_vqs	= vm_del_vqs,
+	.reset_vqs	= vm_reset_vqs,
 	.get_features	= vm_get_features,
 	.finalize_features = vm_finalize_features,
 	.bus_name	= vm_bus_name,
 	.get_shm_region = vm_get_shm_region,
 	.synchronize_cbs = vm_synchronize_cbs,
+	.noirq_safe	= true,
 };
 
 #ifdef CONFIG_PM_SLEEP
@@ -547,14 +582,33 @@ static int virtio_mmio_restore(struct device *dev)
 {
 	struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);
 
-	if (vm_dev->version == 1)
+	if (vm_dev->version == 1 && !vm_dev->vdev.noirq_restore_done)
 		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
 
 	return virtio_device_restore(&vm_dev->vdev);
 }
 
+static int virtio_mmio_freeze_noirq(struct device *dev)
+{
+	struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);
+
+	return virtio_device_freeze_noirq(&vm_dev->vdev);
+}
+
+static int virtio_mmio_restore_noirq(struct device *dev)
+{
+	struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);
+
+	if (vm_dev->version == 1)
+		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
+
+	return virtio_device_restore_noirq(&vm_dev->vdev);
+}
+
 static const struct dev_pm_ops virtio_mmio_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(virtio_mmio_freeze, virtio_mmio_restore)
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(virtio_mmio_freeze_noirq,
+				      virtio_mmio_restore_noirq)
 };
 #endif
 
-- 
2.43.0