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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>
This commit is contained in:
Alex Williamson
2019-02-09 13:43:30 -07:00
parent a390685589
commit 51ef3a004b
3 changed files with 70 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

71
drivers/vfio/pci/vfio_pci.c
View File

@@ -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]);