On 3/20/26 15:29, Paul Menzel wrote:
Dear Petr,
Thank you for your patch.
Am 20.03.26 um 14:53 schrieb Petr Oros:
The IAVF_RXD_LEGACY_L2TAG2_M mask was incorrectly defined as
GENMASK_ULL(63, 32), extracting 32 bits from qw2 instead of the
16-bit VLAN tag. In the legacy Rx descriptor layout, the 2nd L2TAG2
(VLAN tag) occupies bits 63:48 of qw2, not 63:32.
The oversized mask causes FIELD_GET to return a 32-bit value where the
actual VLAN tag sits in bits 31:16. When this value is passed to
iavf_receive_skb() as a u16 parameter, it gets truncated to the lower
16 bits (which contain the 1st L2TAG2, typically zero). As a result,
__vlan_hwaccel_put_tag() is never called and software VLAN interfaces
on VFs receive no traffic.
This affects VFs behind ice PF (VIRTCHNL VLAN v2) when the PF
advertises VLAN stripping into L2TAG2_2 and legacy descriptors are
used.
The flex descriptor path already uses the correct mask
(IAVF_RXD_FLEX_L2TAG2_2_M = GENMASK_ULL(63, 48)).
Do you have a reproducer to verify the fix?
Yes, i have
1. Create 2 VFs on ice PF (echo 2 > sriov_numvfs)
2. Disable spoofchk on both VFs
3. Move each VF into a separate network namespace
4. On each VF: create VLAN interface (e.g. vlan 198), assign IP, bring up
5. Set rx-vlan-offload OFF on both VFs
6. Ping between VLAN interfaces → expect PASS
(VLAN tag stays in packet data, kernel matches in-band)
7. Set rx-vlan-offload ON on both VFs
8. Ping between VLAN interfaces → expect FAIL if bug present
(HW strips VLAN tag into descriptor L2TAG2 field,
wrong mask extracts bits 47:32 instead of 63:48,
truncated to u16 → zero, __vlan_hwaccel_put_tag() never called,
packet delivered to parent interface, not VLAN interface)
Fixes: 2dc8e7c36d80 ("iavf: refactor iavf_clean_rx_irq to support
legacy and flex descriptors")
(That first entered Linux v6.15-rc1, and Linux 6.12 and 6.18 are LTS
series.)
The reproducer works but requires legacy Rx descriptors to be in use.
On modern ice + iavf with full PTP support, flex descriptors are always
negotiated and the buggy legacy path is never reached.
Flex descriptors require all of the following:
- CONFIG_PTP_1588_CLOCK enabled in kernel config
- VIRTCHNL_VF_OFFLOAD_RX_FLEX_DESC granted by PF
- PTP capabilities negotiated (VIRTCHNL_VF_CAP_PTP)
- VIRTCHNL_1588_PTP_CAP_RX_TSTAMP supported
- VIRTCHNL_RXDID_2_FLEX_SQ_NIC present in DDP profile
If any of these conditions is not met, iavf_select_rx_desc_format()
falls back to legacy descriptors (RXDID=1) and the wrong L2TAG2 mask is hit.
In our kernel we ended up in a state where the iavf Rx path refactor was
backported but the full PTP support chain was not. Without PTP,
iavf_ptp_cap_supported() returns false and flex descriptors
are never selected, exposing the bug.
Regards,
Petr
Signed-off-by: Petr Oros <[email protected]>
---
drivers/net/ethernet/intel/iavf/iavf_type.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/intel/iavf/iavf_type.h
b/drivers/net/ethernet/intel/iavf/iavf_type.h
index 1d8cf29cb65ac5..5bb1de1cfd33b1 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_type.h
+++ b/drivers/net/ethernet/intel/iavf/iavf_type.h
@@ -277,7 +277,7 @@ struct iavf_rx_desc {
/* L2 Tag 2 Presence */
#define IAVF_RXD_LEGACY_L2TAG2P_M BIT(0)
/* Stripped S-TAG VLAN from the receive packet */
-#define IAVF_RXD_LEGACY_L2TAG2_M GENMASK_ULL(63, 32)
+#define IAVF_RXD_LEGACY_L2TAG2_M GENMASK_ULL(63, 48)
/* Stripped S-TAG VLAN from the receive packet */
#define IAVF_RXD_FLEX_L2TAG2_2_M GENMASK_ULL(63, 48)
/* The packet is a UDP tunneled packet */
Nice find.
Reviewed-by: Paul Menzel <[email protected]>
Kind regards,
Paul
