linux-kernel - Re: [PATCH v3 4/4] x86/of: Add support for boot time interrupt delivery mode configuration

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Date:   Tue, 22 Nov 2022 11:14:17 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Rahul Tanwar <rtanwar@...linear.com>
Cc:     bigeasy@...utronix.de, robh@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, linux-kernel@...r.kernel.org,
        linux-lgm-soc@...linear.com
Subject: Re: [PATCH v3 4/4] x86/of: Add support for boot time interrupt
 delivery mode configuration

On Tue, Nov 22, 2022 at 03:39:10PM +0800, Rahul Tanwar wrote:
> Presently, init/boot time interrupt delivery mode is enumerated
> only for ACPI enabled systems by parsing MADT table or for older
> systems by parsing MP table. But for OF based x86 systems, it is
> assumed & hardcoded to legacy PIC mode. This is a bug for
> platforms which are OF based but do not use 8259 compliant legacy
> PIC interrupt controller. Such platforms can not even boot because
> of this bug/hardcoding.
> 
> Fix this bug by adding support for configuration of init time
> interrupt delivery mode for x86 OF based systems by introducing a
> new optional boolean property 'intel,virtual-wire-mode' for
> interrupt-controller node of local APIC. This property emulates
> IMCRP Bit 7 of MP feature info byte 2 of MP floating pointer
> structure.
> 
> Defaults to legacy PIC mode if absent. Configures it to virtual
> wire compatibility mode if present.

> Fixes: 3879a6f32948 ("x86: dtb: Add early parsing of IO_APIC")

If it was never working, there is nothing to fix.
OTOH, without Cc: stable@ this is up to stable maintainers to
backport.


> Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

I definitely haven't suggested this fix.

...

The code looks good to me.

-- 
With Best Regards,
Andy Shevchenko