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

[Lucas De Marchi]

On Tue, May 07, 2024 at 06:57:57PM GMT, Michal Wajdeczko wrote:
>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 at intel.com>
>---
> drivers/gpu/drm/xe/xe_sriov.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
>diff --git a/drivers/gpu/drm/xe/xe_sriov.c b/drivers/gpu/drm/xe/xe_sriov.c
>index 1c3fa84b6adb..a274a5fb1401 100644
>--- a/drivers/gpu/drm/xe/xe_sriov.c
>+++ b/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.

Aren't these 2 different things? The PCI layer is reporting SR-IOV
availability as reported by the HW, which doesn't mean the driver
supports it.

Lucas De Marchi

>+		 */
>+		drm_info(&xe->drm, "Support for SR-IOV is not available\n");
>+		pci_sriov_set_totalvfs(pdev, 0);
> 	}
>
> 	xe_assert(xe, !xe->sriov.__mode);
>-- 
>2.43.0
>