[PATCH v4 02/11] vpci: cancel pending map/unmap on vpci removal

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

When a vPCI is removed for a PCI device it is possible that we have
scheduled a delayed work for map/unmap operations for that device.
For example, the following scenario can illustrate the problem:

pci_physdev_op
   pci_add_device
       init_bars -> modify_bars -> defer_map -> raise_softirq(SCHEDULE_SOFTIRQ)
   iommu_add_device <- FAILS
   vpci_remove_device -> xfree(pdev->vpci)

leave_hypervisor_to_guest
   vpci_process_pending: v->vpci.mem != NULL; v->vpci.pdev->vpci == NULL

For the hardware domain we continue execution as the worse that
could happen is that MMIO mappings are left in place when the
device has been deassigned

For unprivileged domains that get a failure in the middle of a vPCI
{un}map operation we need to destroy them, as we don't know in which
state the p2m is. This can only happen in vpci_process_pending for
DomUs as they won't be allowed to call pci_add_device.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

---
Cc: Roger Pau Monné <roger.pau@citrix.com>

New in v4
---
 xen/drivers/vpci/header.c | 15 +++++++++++++--
 xen/drivers/vpci/vpci.c   |  2 ++
 xen/include/xen/vpci.h    |  6 ++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index 40ff79c33f8f..ef538386e95d 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -149,8 +149,7 @@ bool vpci_process_pending(struct vcpu *v)
                         !rc && v->vpci.rom_only);
         spin_unlock(&v->vpci.pdev->vpci->lock);
 
-        rangeset_destroy(v->vpci.mem);
-        v->vpci.mem = NULL;
+        vpci_cancel_pending(v->vpci.pdev);
         if ( rc )
             /*
              * FIXME: in case of failure remove the device from the domain.
@@ -165,6 +164,18 @@ bool vpci_process_pending(struct vcpu *v)
     return false;
 }
 
+void vpci_cancel_pending(const struct pci_dev *pdev)
+{
+    struct vcpu *v = current;
+
+    /* Cancel any pending work now. */
+    if ( v->vpci.mem && v->vpci.pdev == pdev)
+    {
+        rangeset_destroy(v->vpci.mem);
+        v->vpci.mem = NULL;
+    }
+}
+
 static int __init apply_map(struct domain *d, const struct pci_dev *pdev,
                             struct rangeset *mem, uint16_t cmd)
 {
diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 657697fe3406..4e24956419aa 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -51,6 +51,8 @@ void vpci_remove_device(struct pci_dev *pdev)
         xfree(r);
     }
     spin_unlock(&pdev->vpci->lock);
+
+    vpci_cancel_pending(pdev);
     xfree(pdev->vpci->msix);
     xfree(pdev->vpci->msi);
     xfree(pdev->vpci);
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index 3f32de9d7eb3..609d6383b252 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -56,6 +56,7 @@ uint32_t vpci_hw_read32(const struct pci_dev *pdev, unsigned int reg,
  * should not run.
  */
 bool __must_check vpci_process_pending(struct vcpu *v);
+void vpci_cancel_pending(const struct pci_dev *pdev);
 
 struct vpci {
     /* List of vPCI handlers for a device. */
@@ -252,6 +253,11 @@ static inline bool __must_check vpci_process_pending(struct vcpu *v)
     ASSERT_UNREACHABLE();
     return false;
 }
+
+static inline void vpci_cancel_pending(const struct pci_dev *pdev)
+{
+    ASSERT_UNREACHABLE();
+}
 #endif
 
 #endif
-- 
2.25.1