On Thu, 25 Feb 2021 08:21:01 +0800 Coiby Xu wrote:

On Wed, Feb 24, 2021 at 08:48:41AM -0800, Jakub Kicinski wrote:

quoted

On Wed, 24 Feb 2021 19:41:41 +0800 Coiby Xu wrote:  

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I'm not sure if I understand you correctly. Do you mean we shouldn't
disable i40iw for kdump?  

Forgive my ignorance - are the kdump kernels separate builds?

AFAIK we don't build a kernel exclusively for kdump. 

quoted

If they are it'd be better to leave the choice of enabling RDMA
to the user - through appropriate Kconfig options.

i40iw is usually built as a loadable module. So if we want to leave the
choce of enabling RDMA to the user, we could exclude this driver when
building the initramfs for kdump, for example, dracut provides the 
omit_drivers option for this purpose. 

On the other hand, the users expect "crashkernel=auto" to work out of
the box. So i40iw defeats this purpose. 

I'll discuss with my Red Hat team and the Intel team about whether RDMA
is needed for kdump. Thanks for bringing up this issue!

Great, talking to experts here at FB it seems that building a cut-down
kernel for kdump is easier than chasing all the drivers to react to
is_kdump_kernel(). But if you guys need it and Intel is fine with 
the change I won't complain.