* re: mlx4_en: fix endianness with blue frame support
@ 2012-09-18 7:34 Dan Carpenter
2012-09-20 13:46 ` Or Gerlitz
0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2012-09-18 7:34 UTC (permalink / raw)
To: cascardo; +Cc: netdev
Hello Thadeu Lima de Souza Cascardo,
The patch c5d6136e10d6: "mlx4_en: fix endianness with blue frame
support" from Oct 10, 2011, leads to the following warning:
drivers/net/ethernet/mellanox/mlx4/en_tx.c:720 mlx4_en_xmit()
warn: potential memory corrupting cast. 4 vs 2 bytes
That patch introduced a call to cpu_to_be32() and added some endian
notation.
*(__be32 *) (&tx_desc->ctrl.vlan_tag) |= cpu_to_be32(ring->doorbell_qpn);
But it doesn't make sense because the data type is declared as u16 in
the header and we would be corrupting the next elements in the struct
which are ins_vlan and fence_size.
struct mlx4_wqe_ctrl_seg {
__be32 owner_opcode;
__be16 vlan_tag;
u8 ins_vlan;
u8 fence_size;
I guess the reason we get away with it is that the ->doorbell_qpn is
normally less that 65k. But doorbell_qpn is a u32 type so I think there
is a risk here.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: mlx4_en: fix endianness with blue frame support
2012-09-18 7:34 mlx4_en: fix endianness with blue frame support Dan Carpenter
@ 2012-09-20 13:46 ` Or Gerlitz
2012-09-24 19:42 ` Dan Carpenter
0 siblings, 1 reply; 3+ messages in thread
From: Or Gerlitz @ 2012-09-20 13:46 UTC (permalink / raw)
To: Dan Carpenter; +Cc: cascardo, netdev, Yevgeny Petrilin, Eli Cohen
On Tue, Sep 18, 2012 at 10:34 AM, Dan Carpenter
<dan.carpenter@oracle.com> wrote:
> Hello Thadeu Lima de Souza Cascardo,
>
> The patch c5d6136e10d6: "mlx4_en: fix endianness with blue frame
> support" from Oct 10, 2011, leads to the following warning:
> drivers/net/ethernet/mellanox/mlx4/en_tx.c:720 mlx4_en_xmit()
> warn: potential memory corrupting cast. 4 vs 2 bytes
>
> That patch introduced a call to cpu_to_be32() and added some endian notation.
> *(__be32 *) (&tx_desc->ctrl.vlan_tag) |= cpu_to_be32(ring->doorbell_qpn);
> But it doesn't make sense because the data type is declared as u16 in
> the header and we would be corrupting the next elements in the struct
> which are ins_vlan and fence_size.
>
> struct mlx4_wqe_ctrl_seg {
> __be32 owner_opcode;
> __be16 vlan_tag;
> u8 ins_vlan;
> u8 fence_size;
>
> I guess the reason we get away with it is that the ->doorbell_qpn is
> normally less that 65k. But doorbell_qpn is a u32 type so I think there is a risk here.
Dan,
QP numbers are 24 bit in size, under blue-flame setting the QP number
is written
over the "vlan_tag" field and potentially also the "ins_vlan" field of
the control segment,
we can do a little cleanup here with introducing a modified version of
the mlx4_wqe_ctrl_seg
structure over which the cast is made under the blue-flame flow.
Or.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: mlx4_en: fix endianness with blue frame support
2012-09-20 13:46 ` Or Gerlitz
@ 2012-09-24 19:42 ` Dan Carpenter
0 siblings, 0 replies; 3+ messages in thread
From: Dan Carpenter @ 2012-09-24 19:42 UTC (permalink / raw)
To: Or Gerlitz; +Cc: cascardo, netdev, Yevgeny Petrilin, Eli Cohen
On Thu, Sep 20, 2012 at 04:46:51PM +0300, Or Gerlitz wrote:
> On Tue, Sep 18, 2012 at 10:34 AM, Dan Carpenter
> <dan.carpenter@oracle.com> wrote:
> > Hello Thadeu Lima de Souza Cascardo,
> >
> > The patch c5d6136e10d6: "mlx4_en: fix endianness with blue frame
> > support" from Oct 10, 2011, leads to the following warning:
> > drivers/net/ethernet/mellanox/mlx4/en_tx.c:720 mlx4_en_xmit()
> > warn: potential memory corrupting cast. 4 vs 2 bytes
> >
> > That patch introduced a call to cpu_to_be32() and added some endian notation.
> > *(__be32 *) (&tx_desc->ctrl.vlan_tag) |= cpu_to_be32(ring->doorbell_qpn);
> > But it doesn't make sense because the data type is declared as u16 in
> > the header and we would be corrupting the next elements in the struct
> > which are ins_vlan and fence_size.
> >
> > struct mlx4_wqe_ctrl_seg {
> > __be32 owner_opcode;
> > __be16 vlan_tag;
> > u8 ins_vlan;
> > u8 fence_size;
> >
> > I guess the reason we get away with it is that the ->doorbell_qpn is
> > normally less that 65k. But doorbell_qpn is a u32 type so I think there is a risk here.
>
> Dan,
>
> QP numbers are 24 bit in size, under blue-flame setting the QP number
> is written
> over the "vlan_tag" field and potentially also the "ins_vlan" field of
> the control segment,
> we can do a little cleanup here with introducing a modified version of
> the mlx4_wqe_ctrl_seg
> structure over which the cast is made under the blue-flame flow.
>
> Or.
Actually 24 bit big endian would mean they almost always over-write
the fence_size field. It's the highest byte of vlan_tag which would
not be modified.
I'm not sure how this ever worked. Something is confusing here.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2012-09-24 19:43 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2012-09-18 7:34 mlx4_en: fix endianness with blue frame support Dan Carpenter
2012-09-20 13:46 ` Or Gerlitz
2012-09-24 19:42 ` Dan Carpenter
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).