linux-kernel - RE: [PATCH 1/2] x86/fred: Always install system interrupt handler into IDT

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Date: Tue, 25 Jun 2024 19:11:54 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: "Li, Xin3" <xin3.li@...el.com>, Xin Li <xin@...or.com>, Hou Wenlong
 <houwenlong.hwl@...group.com>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>, Ingo Molnar
 <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
 <dave.hansen@...ux.intel.com>, "x86@...nel.org" <x86@...nel.org>, "H.
 Peter
 Anvin" <hpa@...or.com>, Jacob Pan <jacob.jun.pan@...ux.intel.com>,
 "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, Paolo Bonzini
 <pbonzini@...hat.com>
Subject: RE: [PATCH 1/2] x86/fred: Always install system interrupt handler
 into IDT

On Tue, Jun 25 2024 at 17:08, Li, Xin3 wrote:
>> >>> And please put a comment here to explain why this is unconditionally
>> >>> done for IDT.
>> >>
>> >> Wait. If we need this during early boot, then why don't we enable
>> >> FRED earlier?
>> >
>> > Unconditionally call idt_install_sysvec() is still needed, right?
>> 
>> Not when we enable FRED early enough.
>> 
>
> What if FRED is disabled in the kernel command line?
>
> "fred=off" gets parsed in a later stage of the kernel initialization sequence.

You can parse it early on. There are examples for that like encryption
and other things which need to be decided way before the real parsing
happens.

Thanks,

        tglx