[Crash-utility] What is the current state of the 5-level page tables in Crash

[Dou Liyang]

Hi Dave,

At 12/20/2017 02:15 AM, Dave Anderson wrote:
> 
> 
> ----- Original Message -----
>> Dear Dave,
>>
>> I saw your commit
>>
>> 307e7f35f510("First phase of future support for x86_64 5-level page
>> tables.")
>>
>> in crash git-tree. It is the preparatory for x86_64 5-level page tables.
>> There may be more things to be done to support for 5-level.
> 
> Right.  There needs to be a manner of determining very early on whether
> the kernel page tables are using 5-level.  And during crash runtime, there
> needs to be a manner of determining whether each user-space task is using
> 4- or 5-level page tables.  Also, it may be possible/preferable to
> squeeze the 5-level support into the currently existing x86_64_kvtop() and
> x86_64_uvtop() functions instead of using the new xxx_5level() function
> placeholders that I added in the preparatory patch.
> 

It is really helpful to me.

>>
>> I hope to know:
>>
>> 1. What is the current state of the 5-level page table in Crash?
> 
> I have done nothing further beyond than the preparatory steps in that commit.
> 
>>
>> 2. If there are some reason that we should pause the support work of
>> 5-level page tables currently.
> 
> No, not really.  I originally delayed further work because originally it
> was enabled by kernel CONFIG, but as I understand it now, it is enabled by
> a combination of a kernel CONFIG and a boot command line option?  But

I am sorry I just found the CONFIG_X86_5LEVEL, Could you tell me the
name of boot command line option?

> since I have never seen or worked with a kernel with it enabled, I've

Indeed, we only can use it in QEmu now.

> not done anything further.

Yes, I see.

> 
>>
>> 3. Are you already doing it?
> 
> No.  Are you offering to complete the work?
> 

Aha, I am willing to, But I am not familiar with crash, I will try me
best to do it.

Thanks,
	dou