Re: [EXTERNAL] Re: [PATCH net-next,v2] net: mana: Add support for Multi Vports on Bare metal

[Paolo Abeni <pabeni@redhat.com>]

On 5/22/25 2:02 PM, Simon Horman wrote:
> On Wed, May 21, 2025 at 05:28:33PM +0000, Haiyang Zhang wrote:
>>> -----Original Message-----
>>> From: Simon Horman <horms@kernel.org>
>>> Sent: Wednesday, May 21, 2025 10:03 AM
>>> To: Haiyang Zhang <haiyangz@microsoft.com>
>>> Cc: linux-hyperv@vger.kernel.org; netdev@vger.kernel.org; Dexuan Cui
>>> <decui@microsoft.com>; stephen@networkplumber.org; KY Srinivasan
>>> <kys@microsoft.com>; Paul Rosswurm <paulros@microsoft.com>;
>>> olaf@aepfle.de; vkuznets@redhat.com; davem@davemloft.net;
>>> wei.liu@kernel.org; edumazet@google.com; kuba@kernel.org;
>>> pabeni@redhat.com; leon@kernel.org; Long Li <longli@microsoft.com>;
>>> ssengar@linux.microsoft.com; linux-rdma@vger.kernel.org;
>>> daniel@iogearbox.net; john.fastabend@gmail.com; bpf@vger.kernel.org;
>>> ast@kernel.org; hawk@kernel.org; tglx@linutronix.de;
>>> shradhagupta@linux.microsoft.com; andrew+netdev@lunn.ch; Konstantin
>>> Taranov <kotaranov@microsoft.com>; linux-kernel@vger.kernel.org
>>> Subject: [EXTERNAL] Re: [PATCH net-next,v2] net: mana: Add support for
>>> Multi Vports on Bare metal
>>>
>>> On Mon, May 19, 2025 at 09:20:36AM -0700, Haiyang Zhang wrote:
>>>> To support Multi Vports on Bare metal, increase the device config
>>> response
>>>> version. And, skip the register HW vport, and register filter steps,
>>> when
>>>> the Bare metal hostmode is set.
>>>>
>>>> Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
>>>> ---
>>>> v2:
>>>>   Updated comments as suggested by ALOK TIWARI.
>>>>   Fixed the version check.
>>>>
>>>> ---
>>>>  drivers/net/ethernet/microsoft/mana/mana_en.c | 24 ++++++++++++-------
>>>>  include/net/mana/mana.h                       |  4 +++-
>>>>  2 files changed, 19 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c
>>> b/drivers/net/ethernet/microsoft/mana/mana_en.c
>>>> index 2bac6be8f6a0..9c58d9e0bbb5 100644
>>>> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
>>>> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
>>>> @@ -921,7 +921,7 @@ static void mana_pf_deregister_filter(struct
>>> mana_port_context *apc)
>>>>
>>>>  static int mana_query_device_cfg(struct mana_context *ac, u32
>>> proto_major_ver,
>>>>  				 u32 proto_minor_ver, u32 proto_micro_ver,
>>>> -				 u16 *max_num_vports)
>>>> +				 u16 *max_num_vports, u8 *bm_hostmode)
>>>>  {
>>>>  	struct gdma_context *gc = ac->gdma_dev->gdma_context;
>>>>  	struct mana_query_device_cfg_resp resp = {};
>>>> @@ -932,7 +932,7 @@ static int mana_query_device_cfg(struct mana_context
>>> *ac, u32 proto_major_ver,
>>>>  	mana_gd_init_req_hdr(&req.hdr, MANA_QUERY_DEV_CONFIG,
>>>>  			     sizeof(req), sizeof(resp));
>>>>
>>>> -	req.hdr.resp.msg_version = GDMA_MESSAGE_V2;
>>>> +	req.hdr.resp.msg_version = GDMA_MESSAGE_V3;
>>>>
>>>>  	req.proto_major_ver = proto_major_ver;
>>>>  	req.proto_minor_ver = proto_minor_ver;
>>>
>>>> @@ -956,11 +956,16 @@ static int mana_query_device_cfg(struct
>>> mana_context *ac, u32 proto_major_ver,
>>>>
>>>>  	*max_num_vports = resp.max_num_vports;
>>>>
>>>> -	if (resp.hdr.response.msg_version == GDMA_MESSAGE_V2)
>>>> +	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V2)
>>>>  		gc->adapter_mtu = resp.adapter_mtu;
>>>>  	else
>>>>  		gc->adapter_mtu = ETH_FRAME_LEN;
>>>>
>>>> +	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V3)
>>>> +		*bm_hostmode = resp.bm_hostmode;
>>>> +	else
>>>> +		*bm_hostmode = 0;
>>>
>>> Hi,
>>>
>>> Perhaps not strictly related to this patch, but I see
>>> that mana_verify_resp_hdr() is called a few lines above.
>>> And that verifies a minimum msg_version. But I do not see
>>> any verification of the maximum msg_version supported by the code.
>>>
>>> I am concerned about a hypothetical scenario where, say the as yet unknown
>>> version 5 is sent as the version, and the above behaviour is used, while
>>> not being correct.
>>>
>>> Could you shed some light on this?
>>>
>>
>> In driver, we specify the expected reply msg version is v3 here:
>> req.hdr.resp.msg_version = GDMA_MESSAGE_V3;
>>
>> If the HW side is upgraded, it won't send reply msg version higher
>> than expected, which may break the driver.
> 
> Thanks,
> 
> If I understand things correctly the HW side will honour the
> req.hdr.resp.msg_version and thus the SW won't receive anything
> it doesn't expect. Is that right?

@Haiyang, if Simon's interpretation is correct, please change the
version checking in the driver from:

	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V3)

to
	if (resp.hdr.response.msg_version == GDMA_MESSAGE_V3)

As the current code is misleading.

Thanks,

Paolo