RE: [PATCH V2,net-next, 3/3] net: mana: Add support for jumbo frame

Haiyang Zhang
2023-04-12T14:37:46Z

> -----Original Message-----
> From: Jacob Keller <jacob.e.keller@intel.com>
> Sent: Tuesday, April 11, 2023 7:13 PM
> To: Haiyang Zhang <haiyangz@microsoft.com>; linux-hyperv@vger.kernel.org;
> netdev@vger.kernel.org
> Cc: Dexuan Cui <decui@microsoft.com>; 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; Ajay Sharma <sharmaajay@microsoft.com>;
> hawk@kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH V2,net-next, 3/3] net: mana: Add support for jumbo
> frame
>
>
>
> On 4/7/2023 1:59 PM, Haiyang Zhang wrote:
> > During probe, get the hardware-allowed max MTU by querying the device
> > configuration. Users can select MTU up to the device limit.
> > When XDP is in use, limit MTU settings so the buffer size is within
> > one page.
> > Also, to prevent changing MTU fails, and leaves the NIC in a bad state,
> > pre-allocate all buffers before starting the change. So in low memory
> > condition, it will return error, without affecting the NIC.
> >
>
> What happens if XDP gets enabled after MTU larger than PAGE_SIZE is set?
> Will XDP fail to enable in that case?

Yes, XDP program will fail to enable if MTU is too large.

Thanks,
- Haiyang