[PATCH v6 10/12] PCI: liveupdate: Freeze preservation status during shutdown

[David Matlack <dmatlack@google.com>]

Freeze a device's outgoing preservation status (preserved or not
preserved) during shutdown. This enables the PCI core and drivers to
safely make decisions based on the device's preservation status during
shutdown.

Note that pci_liveupdate_freeze() is triggered by the PCI core rather
than from drivers participating in Live Update so that all devices can
have their status frozen (i.e. prevent non-preserved devices from
getting preserved late).

Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/liveupdate.c       | 16 ++++++++++++++++
 drivers/pci/liveupdate.h       |  5 +++++
 drivers/pci/pci-driver.c       |  2 ++
 include/linux/pci_liveupdate.h |  3 +++
 4 files changed, 26 insertions(+)

diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c
index 701276ef6cfb..d404e64a4e55 100644
--- a/drivers/pci/liveupdate.c
+++ b/drivers/pci/liveupdate.c
@@ -297,6 +297,11 @@ static int pci_liveupdate_unpreserve_device(struct pci_ser *ser, struct pci_dev
 {
 	struct pci_dev_ser *dev_ser = dev->liveupdate.outgoing;
 
+	if (dev->liveupdate.frozen) {
+		pci_warn(dev, "Cannot unpreserve device after it is frozen!\n");
+		return -EINVAL;
+	}
+
 	if (!dev_ser) {
 		pci_warn(dev, "Cannot unpreserve device that is not preserved\n");
 		return -EINVAL;
@@ -380,6 +385,11 @@ static int __pci_liveupdate_preserve_device(struct pci_ser *ser, struct pci_dev
 
 static int pci_liveupdate_preserve_device(struct pci_ser *ser, struct pci_dev *dev)
 {
+	if (dev->liveupdate.frozen) {
+		pci_warn(dev, "Cannot preserve device after it is frozen!\n");
+		return -EINVAL;
+	}
+
 	if (dev->liveupdate.outgoing)
 		return pci_liveupdate_preserve_device_again(dev);
 
@@ -653,6 +663,12 @@ void pci_liveupdate_cleanup_device(struct pci_dev *dev)
 	}
 }
 
+void pci_liveupdate_freeze(struct pci_dev *dev)
+{
+	guard(rwsem_write)(&pci_liveupdate.rwsem);
+	dev->liveupdate.frozen = 1;
+}
+
 static int pci_liveupdate_finish_device(struct pci_ser *ser, struct pci_dev *dev)
 {
 	if (!dev->liveupdate.incoming) {
diff --git a/drivers/pci/liveupdate.h b/drivers/pci/liveupdate.h
index 6f21ec50927b..bcb0bc73d684 100644
--- a/drivers/pci/liveupdate.h
+++ b/drivers/pci/liveupdate.h
@@ -13,6 +13,7 @@
 #ifdef CONFIG_PCI_LIVEUPDATE
 void pci_liveupdate_setup_device(struct pci_dev *dev);
 void pci_liveupdate_cleanup_device(struct pci_dev *dev);
+void pci_liveupdate_freeze(struct pci_dev *dev);
 bool pci_liveupdate_scan_bridge_begin(struct pci_bus *bus, struct pci_dev *dev,
 				      int pass);
 void pci_liveupdate_scan_bridge_end(struct pci_dev *dev, int pass);
@@ -28,6 +29,10 @@ static inline void pci_liveupdate_cleanup_device(struct pci_dev *dev)
 {
 }
 
+static inline void pci_liveupdate_freeze(struct pci_dev *dev)
+{
+}
+
 static inline bool pci_liveupdate_scan_bridge_begin(struct pci_bus *bus,
 						    struct pci_dev *dev,
 						    int pass)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index d10ece0889f0..f7a5e65a7c75 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -21,6 +21,7 @@
 #include <linux/acpi.h>
 #include <linux/dma-map-ops.h>
 #include <linux/iommu.h>
+#include "liveupdate.h"
 #include "pci.h"
 #include "pcie/portdrv.h"
 
@@ -536,6 +537,7 @@ static void pci_device_shutdown(struct device *dev)
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct pci_driver *drv = pci_dev->driver;
 
+	pci_liveupdate_freeze(pci_dev);
 	pm_runtime_resume(dev);
 
 	if (drv && drv->shutdown)
diff --git a/include/linux/pci_liveupdate.h b/include/linux/pci_liveupdate.h
index 2446c6d237ca..150993405754 100644
--- a/include/linux/pci_liveupdate.h
+++ b/include/linux/pci_liveupdate.h
@@ -24,6 +24,8 @@
  * @was_preserved: True if this struct pci_dev was preserved by the previous
  *                 kernel. Unlike @incoming, this field is not cleared after
  *                 the device is finished participating in Live Update.
+ * @frozen: True if the outgoing preservation status of this device is frozen
+ *          and thus cannot be changed.
  */
 struct pci_liveupdate {
 	struct pci_dev_ser *outgoing;
@@ -31,6 +33,7 @@ struct pci_liveupdate {
 	u16 acs_ctrl;
 	bool inherit_buses;
 	bool was_preserved;
+	bool frozen;
 };
 
 struct pci_dev;
-- 
2.54.0.746.g67dd491aae-goog