[PATCH] drm/xe/pf: Restore TotalVFs

[Michal Wajdeczko]

If we update TotalVFs to a new value and fail the .probe() then
the PCI subsystem will not restore original value, which might
impact next .probe() attempt. As a backup plan, use managed action
to restore it ourselves.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
Cc: Piotr Piórkowski <piotr.piorkowski at intel.com>
---
Attempt to fix that at PCI layer is here [1], but until it will be
available for us, we can still fix that on our side.

[1] https://lore.kernel.org/linux-pci/20240715102835.1286-1-michal.wajdeczko@intel.com/
---
 drivers/gpu/drm/xe/xe_sriov_pf.c | 48 +++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_sriov_pf.c b/drivers/gpu/drm/xe/xe_sriov_pf.c
index 0f721ae17b26..d61933770f1c 100644
--- a/drivers/gpu/drm/xe/xe_sriov_pf.c
+++ b/drivers/gpu/drm/xe/xe_sriov_pf.c
@@ -17,12 +17,40 @@ static unsigned int wanted_max_vfs(struct xe_device *xe)
 	return xe_modparam.max_vfs;
 }
 
-static int pf_reduce_totalvfs(struct xe_device *xe, int limit)
+static void restore_totalvfs(void *arg)
+{
+	struct xe_device *xe = arg;
+	struct device *dev = xe->drm.dev;
+	struct pci_dev *pdev = to_pci_dev(dev);
+	int totalvfs = xe->sriov.pf.device_total_vfs;
+
+	xe_sriov_dbg_verbose(xe, "restoring totalvfs to %d\n", totalvfs);
+	pci_sriov_set_totalvfs(pdev, totalvfs);
+}
+
+static int pf_reduce_totalvfs(struct xe_device *xe, u16 limit)
 {
 	struct device *dev = xe->drm.dev;
 	struct pci_dev *pdev = to_pci_dev(dev);
 	int err;
 
+	xe->sriov.pf.device_total_vfs = pci_sriov_get_totalvfs(pdev);
+	xe->sriov.pf.driver_max_vfs = limit;
+
+	xe_sriov_dbg_verbose(xe, "reducing totalvfs from %u to %u\n",
+			     xe->sriov.pf.device_total_vfs,
+			     xe->sriov.pf.driver_max_vfs);
+
+	/*
+	 * XXX: If we update TotalVFs to a new value and fail the .probe()
+	 * then the PCI subsystem might not restore original TotalVFs value,
+	 * which might impact next .probe() attempt. As a backup plan, use
+	 * managed action to restore it ourselves.
+	 *
+	 * Note that it's not critical if registering that action fails.
+	 */
+	devm_add_action(xe->drm.dev, restore_totalvfs, xe);
+
 	err = pci_sriov_set_totalvfs(pdev, limit);
 	if (err)
 		xe_sriov_notice(xe, "Failed to set number of VFs to %d (%pe)\n",
@@ -37,6 +65,14 @@ static bool pf_continue_as_native(struct xe_device *xe, const char *why)
 	return false;
 }
 
+static bool pf_continue_ready(struct xe_device *xe, u16 max_vfs)
+{
+	xe_assert(xe, max_vfs > 0);
+	xe_sriov_dbg(xe, "preparing for %u VF%s\n", max_vfs, str_plural(max_vfs));
+	pf_reduce_totalvfs(xe, max_vfs);
+	return true;
+}
+
 /**
  * xe_sriov_pf_readiness - Check if PF functionality can be enabled.
  * @xe: the &xe_device to check
@@ -58,18 +94,16 @@ bool xe_sriov_pf_readiness(struct xe_device *xe)
 	if (!dev_is_pf(dev))
 		return false;
 
+	if (!totalvfs)
+		return pf_continue_as_native(xe, "no VFs reported");
+
 	if (!xe_device_uc_enabled(xe))
 		return pf_continue_as_native(xe, "Guc submission disabled");
 
 	if (!newlimit)
 		return pf_continue_as_native(xe, "all VFs disabled");
 
-	pf_reduce_totalvfs(xe, newlimit);
-
-	xe->sriov.pf.device_total_vfs = totalvfs;
-	xe->sriov.pf.driver_max_vfs = newlimit;
-
-	return true;
+	return pf_continue_ready(xe, newlimit);
 }
 
 /**
-- 
2.43.0