Re: [PATCH 00/11] x86: Supervisor Mode Access Prevention

[Eric W. Biederman]

"H. Peter Anvin" <hpa@xxxxxxxxxxxxxxx> writes:

> On 09/21/2012 03:07 PM, Eric W. Biederman wrote:
>> 
>> Have you tested kexec in this environment?
>> 
>> This is the kind of cpu feature that when we enable it, frequently we
>> have to do something on the kexec path.
>> 
>> At a quick skim it looks like the kexec path is using kernel page table
>> entries and clearing all bits from cr4 except X86_CR4_PAE so I don't
>> actually expect this change will require anything on the kexec path.
>> 
>
> I have not, no, but as you quite correctly point out that shouldn't
> affect things.
>
> We should also change the kernel to start clean with CR4 -- the purpose
> of CR4 is to indicate which CPU features the OS is opting into.
>
> I think we do on x86-64 but not on x86-32 at the moment.
>
> This is an unrelated problem, though, and can be addressed later.

Agreed.  I just was just curious where things stood.

Eric

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