linux-kernel - Re: [PATCH v10 01/15] x86/cpu: Enumerate the LASS feature bits

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Message-ID: <e82b48b9-5566-4bf2-9b9e-ee529d59e9b5@intel.com>
Date: Tue, 7 Oct 2025 13:49:12 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "tglx@...utronix.de"
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Subject: Re: [PATCH v10 01/15] x86/cpu: Enumerate the LASS feature bits

On 10/7/2025 11:19 AM, Edgecombe, Rick P wrote:
>> LASS provides the same mode-based protections as paging but without
>> traversing the paging structures. Because the protections are enforced
>> pre-paging, an attacker will not be able to derive paging-based timing
> 
> Nit: pre-page walk maybe? Otherwise it could sound like before paging is enabled
> during boot.
> 

How about: ... protections are enforced prior to page walks, an ...

>>  
>> +config X86_DISABLED_FEATURE_LASS
>> +	def_bool y
>> +	depends on X86_32
>> +
> 
> All the other ones in the file are !X86_64. Why do this one X86_32?
> 

The double negation (DISABLED and !X86_64) was harder to follow when
this was initially posted.

https://lore.kernel.org/lkml/73796800-819b-4433-b0ef-db852336d7a4@zytor.com/
https://lore.kernel.org/lkml/756e93a2-7e42-4323-ae21-a5437e71148e@infradead.org/

I don't have a strong preference. I guess the inconsistency makes it
confusing as well. Will change it back to !X86_64 unless Xin objects.