[RFC KERNEL PATCH v3 1/3] xen/pci: Add xen_reset_device_state function

[Jiqian Chen <Jiqian.Chen@xxxxxxx>]

When device on dom0 side has been reset, the vpci on Xen side
won't get notification, so that the cached state in vpci is
all out of date with the real device state.
To solve that problem, add a new function to clear all vpci
device state when device is reset on dom0 side.

And call that function in pcistub_init_device. Because when
using "pci-assignable-add" to assign a passthrough device in
Xen, it will reset passthrough device and the vpci state will
out of date, and then device will fail to restore bar state.

Co-developed-by: Huang Rui <ray.huang@xxxxxxx>
Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
---
 drivers/xen/pci.c                  | 12 ++++++++++++
 drivers/xen/xen-pciback/pci_stub.c |  4 ++++
 include/xen/interface/physdev.h    |  8 ++++++++
 include/xen/pci.h                  |  6 ++++++
 4 files changed, 30 insertions(+)

diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
index 72d4e3f193af..e9b30bc09139 100644
--- a/drivers/xen/pci.c
+++ b/drivers/xen/pci.c
@@ -177,6 +177,18 @@ static int xen_remove_device(struct device *dev)
 	return r;
 }
 
+int xen_reset_device_state(const struct pci_dev *dev)
+{
+	struct physdev_pci_device device = {
+		.seg = pci_domain_nr(dev->bus),
+		.bus = dev->bus->number,
+		.devfn = dev->devfn
+	};
+
+	return HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_state_reset, &device);
+}
+EXPORT_SYMBOL_GPL(xen_reset_device_state);
+
 static int xen_pci_notifier(struct notifier_block *nb,
 			    unsigned long action, void *data)
 {
diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index e34b623e4b41..24f599eaec14 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -421,6 +421,10 @@ static int pcistub_init_device(struct pci_dev *dev)
 	else {
 		dev_dbg(&dev->dev, "resetting (FLR, D3, etc) the device\n");
 		__pci_reset_function_locked(dev);
+		if (!xen_pv_domain())
+			err = xen_reset_device_state(dev);
+		if (err)
+			goto config_release;
 		pci_restore_state(dev);
 	}
 	/* Now disable the device (this also ensures some private device
diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
index a237af867873..bed53afc4c52 100644
--- a/include/xen/interface/physdev.h
+++ b/include/xen/interface/physdev.h
@@ -256,6 +256,14 @@ struct physdev_pci_device_add {
  */
 #define PHYSDEVOP_prepare_msix          30
 #define PHYSDEVOP_release_msix          31
+/*
+ * On PVH dom0, when device is reset, the vpci on Xen side
+ * won't get notification, so that the cached state in vpci is
+ * all out of date with the real device state. Use this to reset
+ * the vpci state of device.
+ */
+#define PHYSDEVOP_pci_device_state_reset     32
+
 struct physdev_pci_device {
     /* IN */
     uint16_t seg;
diff --git a/include/xen/pci.h b/include/xen/pci.h
index b8337cf85fd1..b2e2e856efd6 100644
--- a/include/xen/pci.h
+++ b/include/xen/pci.h
@@ -4,10 +4,16 @@
 #define __XEN_PCI_H__
 
 #if defined(CONFIG_XEN_DOM0)
+int xen_reset_device_state(const struct pci_dev *dev);
 int xen_find_device_domain_owner(struct pci_dev *dev);
 int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain);
 int xen_unregister_device_domain_owner(struct pci_dev *dev);
 #else
+static inline int xen_reset_device_state(const struct pci_dev *dev)
+{
+	return -1;
+}
+
 static inline int xen_find_device_domain_owner(struct pci_dev *dev)
 {
 	return -1;
-- 
2.34.1