vfio/pci: Restore device state on PM transition

PCI core handles save and restore of device state around reset, but
when using pci_set_power_state() we can unintentionally trigger a soft
reset of the device, where PCI core only restores the BAR state.  If
we're using vfio-pci's idle D3 support to try to put devices into low
power when unused, this might trigger a reset when the device is woken
for use.  Also power state management by the user, or within a guest,
can put the device into D3 power state with potentially limited
ability to restore the device if it should undergo a reset.  The PCI
spec does not define the extent of a soft reset and many devices
reporting soft reset on D3->D0 transition do not undergo a PCI config
space reset.  It's therefore assumed safe to unconditionally restore
the remainder of the state if the device indicates soft reset
support, even on a user initiated wakeup.

Implement a wrapper in vfio-pci to tag devices reporting PM reset
support, save their state on transitions into D3 and restore on
transitions back to D0.

Reported-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index ff60bd1..84b593b 100644 (file)
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -209,6 +209,57 @@ static bool vfio_pci_nointx(struct pci_dev *pdev)
        return false;
 }
 
+static void vfio_pci_probe_power_state(struct vfio_pci_device *vdev)
+{
+       struct pci_dev *pdev = vdev->pdev;
+       u16 pmcsr;
+
+       if (!pdev->pm_cap)
+               return;
+
+       pci_read_config_word(pdev, pdev->pm_cap + PCI_PM_CTRL, &pmcsr);
+
+       vdev->needs_pm_restore = !(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET);
+}
+
+/*
+ * pci_set_power_state() wrapper handling devices which perform a soft reset on
+ * D3->D0 transition.  Save state prior to D0/1/2->D3, stash it on the vdev,
+ * restore when returned to D0.  Saved separately from pci_saved_state for use
+ * by PM capability emulation and separately from pci_dev internal saved state
+ * to avoid it being overwritten and consumed around other resets.
+ */
+int vfio_pci_set_power_state(struct vfio_pci_device *vdev, pci_power_t state)
+{
+       struct pci_dev *pdev = vdev->pdev;
+       bool needs_restore = false, needs_save = false;
+       int ret;
+
+       if (vdev->needs_pm_restore) {
+               if (pdev->current_state < PCI_D3hot && state >= PCI_D3hot) {
+                       pci_save_state(pdev);
+                       needs_save = true;
+               }
+
+               if (pdev->current_state >= PCI_D3hot && state <= PCI_D0)
+                       needs_restore = true;
+       }
+
+       ret = pci_set_power_state(pdev, state);
+
+       if (!ret) {
+               /* D3 might be unsupported via quirk, skip unless in D3 */
+               if (needs_save && pdev->current_state >= PCI_D3hot) {
+                       vdev->pm_save = pci_store_saved_state(pdev);
+               } else if (needs_restore) {
+                       pci_load_and_free_saved_state(pdev, &vdev->pm_save);
+                       pci_restore_state(pdev);
+               }
+       }
+
+       return ret;
+}
+
 static int vfio_pci_enable(struct vfio_pci_device *vdev)
 {
        struct pci_dev *pdev = vdev->pdev;
@@ -216,7 +267,7 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
        u16 cmd;
        u8 msix_pos;
 
-       pci_set_power_state(pdev, PCI_D0);
+       vfio_pci_set_power_state(vdev, PCI_D0);
 
        /* Don't allow our initial saved state to include busmaster */
        pci_clear_master(pdev);
@@ -407,7 +458,7 @@ out:
        vfio_pci_try_bus_reset(vdev);
 
        if (!disable_idle_d3)
-               pci_set_power_state(pdev, PCI_D3hot);
+               vfio_pci_set_power_state(vdev, PCI_D3hot);
 }
 
 static void vfio_pci_release(void *device_data)
@@ -1286,6 +1337,8 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
                                        vfio_pci_set_vga_decode(vdev, false));
        }
 
+       vfio_pci_probe_power_state(vdev);
+
        if (!disable_idle_d3) {
                /*
                 * pci-core sets the device power state to an unknown value at
@@ -1296,8 +1349,8 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
                 * be able to get to D3.  Therefore first do a D0 transition
                 * before going to D3.
                 */
-               pci_set_power_state(pdev, PCI_D0);
-               pci_set_power_state(pdev, PCI_D3hot);
+               vfio_pci_set_power_state(vdev, PCI_D0);
+               vfio_pci_set_power_state(vdev, PCI_D3hot);
        }
 
        return ret;
@@ -1316,6 +1369,11 @@ static void vfio_pci_remove(struct pci_dev *pdev)
        vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
        kfree(vdev->region);
        mutex_destroy(&vdev->ioeventfds_lock);
+
+       if (!disable_idle_d3)
+               vfio_pci_set_power_state(vdev, PCI_D0);
+
+       kfree(vdev->pm_save);
        kfree(vdev);
 
        if (vfio_pci_is_vga(pdev)) {
@@ -1324,9 +1382,6 @@ static void vfio_pci_remove(struct pci_dev *pdev)
                                VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM |
                                VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM);
        }
-
-       if (!disable_idle_d3)
-               pci_set_power_state(pdev, PCI_D0);
 }
 
 static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
@@ -1551,7 +1606,7 @@ put_devs:
                        tmp->needs_reset = false;
 
                        if (tmp != vdev && !disable_idle_d3)
-                               pci_set_power_state(tmp->pdev, PCI_D3hot);
+                               vfio_pci_set_power_state(tmp, PCI_D3hot);
                }
 
                vfio_device_put(devs.devices[i]);

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index 423ea1f..e82b511 100644 (file)
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -691,7 +691,7 @@ static int vfio_pm_config_write(struct vfio_pci_device *vdev, int pos,
                        break;
                }
 
-               pci_set_power_state(vdev->pdev, state);
+               vfio_pci_set_power_state(vdev, state);
        }
 
        return count;

diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 8c0009f..1812cf2 100644 (file)
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -114,7 +114,9 @@ struct vfio_pci_device {
        bool                    has_vga;
        bool                    needs_reset;
        bool                    nointx;
+       bool                    needs_pm_restore;
        struct pci_saved_state  *pci_saved_state;
+       struct pci_saved_state  *pm_save;
        struct vfio_pci_reflck  *reflck;
        int                     refcnt;
        int                     ioeventfds_nr;
@@ -161,6 +163,10 @@ extern int vfio_pci_register_dev_region(struct vfio_pci_device *vdev,
                                        unsigned int type, unsigned int subtype,
                                        const struct vfio_pci_regops *ops,
                                        size_t size, u32 flags, void *data);
+
+extern int vfio_pci_set_power_state(struct vfio_pci_device *vdev,
+                                   pci_power_t state);
+
 #ifdef CONFIG_VFIO_PCI_IGD
 extern int vfio_pci_igd_init(struct vfio_pci_device *vdev);
 #else