Re: [PATCH 1/6] arm: make it possible to disable more kconfig options

[Julien Grall <julien.grall@arm.com>]

Hi,

On 05/21/2018 08:58 PM, Stefano Stabellini wrote:
> On Thu, 19 Apr 2018, Julien Grall wrote:
>>> +
>>> +config HAS_MEM_ACCESS
>>> +	bool
>>> +	prompt "Memory Access and VM events"
>>> +	default y
>>
>> Most of the memaccess code is not protected by HAS_MEM_ACCESS.  So you are
>> going to drop just a couple of hundreds line. Not sure if it is worth it in
>> the actual state.
> 
> Yes, the LOC count it is not worth it today, but I would still like to
> make it selectable because I don't want Xen to come to rely on having
> HAS_MEM_ACCESS enabled all the time. !MEM_ACCESS is a good and valid
> configuration. Also, we can go forward in making more stuff protected by
> HAS_MEM_ACCESS soon.

The common code already doesn't rely on memaccess thanks to when Arm was 
not support it. While I agree that we don't want HAS_MEM_ACCESS enabled 
all the time, I question the usefulness of that possibility today. What 
you are going to remove is about ~150 lines of pumbling to the 
userspace. That's it.

All the meat (and complexity) of memaccess is still here (~500 lines). 
You can achieve the same situation with using XSM. So I don't see the 
real benefits of it here.

It would be better to first guard all memaccess code and then expose the 
config if we still think it is useful.

Cheers,

-- 
Julien Grall

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