linux-kernel - Re: [PATCH] x86/boot/compressed: Register NMI handler in EFI boot loader

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Message-ID: <Y71FJ+G0NGQe3Ppq@gmail.com>
Date:   Tue, 10 Jan 2023 11:59:51 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Zeng Heng <zengheng4@...wei.com>
Cc:     michael.roth@....com, bp@...en8.de, hpa@...or.com,
        tglx@...utronix.de, sathyanarayanan.kuppuswamy@...ux.intel.com,
        kirill.shutemov@...ux.intel.com, jroedel@...e.de,
        keescook@...omium.org, mingo@...hat.com,
        dave.hansen@...ux.intel.com, brijesh.singh@....com,
        linux-kernel@...r.kernel.org, x86@...nel.org, liwei391@...wei.com
Subject: Re: [PATCH] x86/boot/compressed: Register NMI handler in EFI boot
 loader


* Zeng Heng <zengheng4@...wei.com> wrote:

> +void do_boot_nmi_fault(struct pt_regs *regs, unsigned long error_code)
> +{
> +	/* ignore */
> +}
> diff --git a/arch/x86/boot/compressed/idt_64.c b/arch/x86/boot/compressed/idt_64.c
> index 6debb816e83d..b169c9728d52 100644
> --- a/arch/x86/boot/compressed/idt_64.c
> +++ b/arch/x86/boot/compressed/idt_64.c
> @@ -60,6 +60,7 @@ void load_stage2_idt(void)
>  {
>  	boot_idt_desc.address = (unsigned long)boot_idt;
>  
> +	set_idt_entry(X86_TRAP_NMI, boot_nmi_fault);
>  	set_idt_entry(X86_TRAP_PF, boot_page_fault);

So it's a bit sad to install a dummy handler that does nothing, while 
something clearly sent an NMI and expects an intelligent reaction - OTOH 
the unexpected NMIs from from watchdog during a kdump clearly make things 
worse by crashing the bootup.

Anyway, I cannot think of a better response here that the boot loading code 
could do either, so I've applied your fix to tip:x86/boot.

Thanks,

	Ingo