Re: [PATCH v3 1/3] x86/cpu: Enable FSGSBASE early in cpu_init_exception_handling()

[Sohil Mehta]

On 3/18/2026 8:53 AM, Dave Hansen wrote:
> On 3/18/26 08:39, Borislav Petkov wrote:
>> On Wed, Mar 18, 2026 at 06:54:46AM -0700, Sohil Mehta wrote:
>>> It would be more accurate to say ".. before any exceptions that uses
>>> paranoid_entry() can occur.."
>>>
>>> I think early exceptions such #VC can still occur and the
>>> bringup_idt_table is set up to handle those.
>> I really don't understand what the splitting of hairs is supposed to bring
>> here?!
>>
>> The commit message is more than clear and overly detailed - I even thought of
>> shortening it because it went too long...
> 
> Yeah, while Sohil's suggested addition is technically correct, the
> suggestion is a _bit_ too detailed for my taste. I'm OK leaving it like
> Nikunj's original version.


Sorry about the churn.

While reviewing the patch, I was trying to understand the difference
between the early exception handlers and the one setup by
cpu_init_exception_handling() on BSP and APs. It caught my attention
that the code comment said, "Enable the feature (FSGSBASE) before any
exceptions occur."

I got a bit carried away with the technicalities!