* Re: [Intel-wired-lan] [PATCH net v1] ice: fix undersized tx_flags field
[not found] <20230411073707.19230-1-jan.sokolowski@intel.com>
@ 2023-04-12 16:49 ` Alexander Lobakin
2023-04-17 10:16 ` Sokolowski, Jan
0 siblings, 1 reply; 2+ messages in thread
From: Alexander Lobakin @ 2023-04-12 16:49 UTC (permalink / raw)
To: Jan Sokolowski; +Cc: intel-wired-lan, netdev
From: Jan Sokolowski <jan.sokolowski@intel.com>
Date: Tue, 11 Apr 2023 09:37:07 +0200
Please always add original authors to Ccs when you modify some code. I
found this mail only by scrolling IWL, while I should've got it from the
start.
+ Cc netdev (no idea why you didn't do that)
> As not all ICE_TX_FLAGS_* fit in current 16-bit limited
> tx_flags field, some flags would not properly apply.
Could you give more details here? With the actual definitions and also
how it was found and what's the regression is.
I found that there's VLAN tag which uses upper 16 bits only by browsing
the code, while I'd say you should've written it here.
>
> Fix that by removing 16 bit limitation.
>
> Signed-off-by: Jan Sokolowski <jan.sokolowski@intel.com>
> Fixes: aa1d3faf71a6 ("ice: Robustify cleaning/completing XDP Tx buffers")
Your SoB must go last, i.e. "Fixes:" should be placed above it.
> ---
> drivers/net/ethernet/intel/ice/ice_txrx.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
> index fff0efe28373..46c108cc5283 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.h
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
> @@ -183,7 +183,7 @@ struct ice_tx_buf {
> unsigned int nr_frags; /* used for mbuf XDP */
> };
> u32 type:16; /* &ice_tx_buf_type */
> - u32 tx_flags:16;
> + u32 tx_flags;
Please always provide pahole output when you change fields
size/structure. Here you create a 16-bit hole and increase structure
size with no mentioning.
I wouldn't say the fix is optimal. From what I see, we have such flags
(correct me if I'm wrong):
TSO BIT(0)
[bits 1-7 are used]
OUTER_SINGLE_VLAN BIT(8)
[bits 9-15 are UNused]
VLAN_S (shift) 16
[bits 16-31 are used for VLAN tag]
So you have 7 free bits to reuse for &ice_tx_buf_type, but you just
restored the before-commit ::tx_flags size =\
I would do the following:
u32 tx_flags:12;
u32 type:4;
u32 vid:16;
* no structure size change (even no layout change);
* ::type range is 0-15 -- more than enough, as the last &ice_tx_buf_type
value is 6;
* ::tx_flags still has 3 free bits left (9, 10, and 11);
* ::vid makes it easier to set a VLAN tag (no explicit masking-shifting,
just don't forget to adjust the places where %ICE_TX_VLAN_{M,S} are
used).
Don't just use "first that works" approach =\
> DEFINE_DMA_UNMAP_LEN(len);
> DEFINE_DMA_UNMAP_ADDR(dma);
> };
Thanks,
Olek
^ permalink raw reply [flat|nested] 2+ messages in thread
* RE: [Intel-wired-lan] [PATCH net v1] ice: fix undersized tx_flags field
2023-04-12 16:49 ` [Intel-wired-lan] [PATCH net v1] ice: fix undersized tx_flags field Alexander Lobakin
@ 2023-04-17 10:16 ` Sokolowski, Jan
0 siblings, 0 replies; 2+ messages in thread
From: Sokolowski, Jan @ 2023-04-17 10:16 UTC (permalink / raw)
To: Lobakin, Aleksander; +Cc: intel-wired-lan, netdev
From: Lobakin, Aleksander <aleksander.lobakin@intel.com>
Sent: Wednesday, April 12, 2023 6:49 PM
To: Sokolowski, Jan <jan.sokolowski@intel.com>
Cc: intel-wired-lan@lists.osuosl.org; netdev@vger.kernel.org
>Subject: Re: [Intel-wired-lan] [PATCH net v1] ice: fix undersized tx_flags field
>>From: Jan Sokolowski <jan.sokolowski@intel.com>
>>Date: Tue, 11 Apr 2023 09:37:07 +0200
>
>Please always add original authors to Ccs when you modify some code. I
>found this mail only by scrolling IWL, while I should've got it from the
>start.
>
>+ Cc netdev (no idea why you didn't do that)
>> As not all ICE_TX_FLAGS_* fit in current 16-bit limited
>> tx_flags field, some flags would not properly apply.
>
>Could you give more details here? With the actual definitions and also
>how it was found and what's the regression is.
>I found that there's VLAN tag which uses upper 16 bits only by browsing
>the code, while I'd say you should've written it here.
The definitions are ICE_TX_FLAGS_VLAN_* ones, for example ICE_TX_FLAGS_VLAN_M that is a
0xffff0000 mask.
The regression found was with some vlan traffic no longer passing through after commit
aa1d3faf71a6 ("ice: Robustify cleaning/completing XDP Tx buffers")
>>
>> Fix that by removing 16 bit limitation.
>>
>> Signed-off-by: Jan Sokolowski <jan.sokolowski@intel.com>
>> Fixes: aa1d3faf71a6 ("ice: Robustify cleaning/completing XDP Tx buffers")
>
>Your SoB must go last, i.e. "Fixes:" should be placed above it.
>
>> ---
>> drivers/net/ethernet/intel/ice/ice_txrx.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
>> index fff0efe28373..46c108cc5283 100644
>> --- a/drivers/net/ethernet/intel/ice/ice_txrx.h
>> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
>> @@ -183,7 +183,7 @@ struct ice_tx_buf {
>> unsigned int nr_frags; /* used for mbuf XDP */
>> };
>> u32 type:16; /* &ice_tx_buf_type */
>> - u32 tx_flags:16;
>> + u32 tx_flags;
>
>Please always provide pahole output when you change fields
>size/structure. Here you create a 16-bit hole and increase structure
>size with no mentioning.
Ok, will do that.
>I wouldn't say the fix is optimal. From what I see, we have such flags
>(correct me if I'm wrong):
>
>TSO BIT(0)
>[bits 1-7 are used]
>OUTER_SINGLE_VLAN BIT(8)
>[bits 9-15 are UNused]
>VLAN_S (shift) 16
>[bits 16-31 are used for VLAN tag]
>
>So you have 7 free bits to reuse for &ice_tx_buf_type, but you just
>restored the before-commit ::tx_flags size =\
>I would do the following:
>
> u32 tx_flags:12;
> u32 type:4;
> u32 vid:16;
Ok, will try to refactor it in this way and see whether it'll work.
>* no structure size change (even no layout change);
>* ::type range is 0-15 -- more than enough, as the last &ice_tx_buf_type
> value is 6;
>* ::tx_flags still has 3 free bits left (9, 10, and 11);
>* ::vid makes it easier to set a VLAN tag (no explicit masking-shifting,
> just don't forget to adjust the places where %ICE_TX_VLAN_{M,S} are
> used).
>
>Don't just use "first that works" approach =\
>
>> DEFINE_DMA_UNMAP_LEN(len);
>> DEFINE_DMA_UNMAP_ADDR(dma);
>> };
>
>Thanks,
>Olek
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-04-12 16:49 ` [Intel-wired-lan] [PATCH net v1] ice: fix undersized tx_flags field Alexander Lobakin
2023-04-17 10:16 ` Sokolowski, Jan
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