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Subject[PATCH] vfio/pci: Restore device state on PM transition
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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>
---
drivers/vfio/pci/vfio_pci.c | 71 +++++++++++++++++++++++++++++++----
drivers/vfio/pci/vfio_pci_config.c | 2 -
drivers/vfio/pci/vfio_pci_private.h | 6 +++
3 files changed, 70 insertions(+), 9 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index ff60bd1ea587..84b593b9fb1f 100644
--- 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 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
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 @@ static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)
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 423ea1f98441..e82b51114687 100644
--- 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 8c0009f00818..1812cf22fc4f 100644
--- 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
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