drm/xe/pf: Don't advertise support to enable VFs if not ready

Even if we have not enabled SR-IOV support using the platform
specific has_sriov flag, the hardware may still report SR-IOV
capability and the PCI layer may wrongly advertise driver support
to enable VFs.  Explicitly reset the number of supported VFs to
zero to avoid confusion.

Applications may read the /sys/bus/pci/devices/.../sriov_totalvfs
prior to enabling VFs using the sriov_numvfs to check if such an
operation is possible.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240507165757.2835-1-michal.wajdeczko@intel.com

drivers/gpu/drm/xe/xe_sriov.c

@@ -53,6 +53,7 @@ static bool test_is_vf(struct xe_device *xe)
  */
 void xe_sriov_probe_early(struct xe_device *xe)
 {
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
 	enum xe_sriov_mode mode = XE_SRIOV_MODE_NONE;
 	bool has_sriov = xe->info.has_sriov;
 
@@ -61,6 +62,16 @@ void xe_sriov_probe_early(struct xe_device *xe)
 			mode = XE_SRIOV_MODE_VF;
 		else if (xe_sriov_pf_readiness(xe))
 			mode = XE_SRIOV_MODE_PF;
+	} else if (pci_sriov_get_totalvfs(pdev)) {
+		/*
+		 * Even if we have not enabled SR-IOV support using the
+		 * platform specific has_sriov flag, the hardware may still
+		 * report SR-IOV capability and the PCI layer may wrongly
+		 * advertise driver support to enable VFs. Explicitly reset
+		 * the number of supported VFs to zero to avoid confusion.
+		 */
+		drm_info(&xe->drm, "Support for SR-IOV is not available\n");
+		pci_sriov_set_totalvfs(pdev, 0);
 	}
 
 	xe_assert(xe, !xe->sriov.__mode);