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Re: [net-next 1/2] xen-netback: add module parameter to disable ctrl-ring





Leon Romanovsky 於 2021/3/14 11:04 寫道:
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On Fri, Mar 12, 2021 at 09:36:59PM +0100, Andrew Lunn wrote:
On Fri, Mar 12, 2021 at 04:18:02PM +0100, Hsu, Chiahao wrote:
Andrew Lunn 於 2021/3/12 15:52 寫道:
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On Thu, Mar 11, 2021 at 10:59:44PM +0000, ChiaHao Hsu wrote:
In order to support live migration of guests between kernels
that do and do not support 'feature-ctrl-ring', we add a
module parameter that allows the feature to be disabled
at run time, instead of using hardcode value.
The default value is enable.
Hi ChiaHao

There is a general dislike for module parameters. What other mechanisms
have you looked at? Would an ethtool private flag work?

       Andrew

Hi Andrew,

I can survey other mechanisms, however before I start doing that,

could you share more details about what the problem is with using module
parameters? thanks.
It is not very user friendly. No two kernel modules use the same
module parameters. Often you see the same name, but different
meaning. There is poor documentation, you often need to read the
kernel sources it figure out what it does, etc.
+1, It is also global parameter to whole system/devices that use this
module, which is rarely what users want.

Thanks

Hi,
I think I would say the current implementation(modparams) isappropriate
after reviewing it again.

We are talking about 'feature leveling', a way to support live migrationof guest between kernels that do and do not support the features. So we want to refrain
fromadding the features if guest would be migrated to the kernel which does
not support the feature. Everythingshould be done (in probe function) before
frontend connects, and this is why ethtool is not appropriate for this.

Thanks





 


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