linux-kernel - Re: [tip: irq/core] x86: Select HARDIRQS_SW

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Message-ID: <231875e7-fc72-edb4-a4de-fc7cfc3cdca3@redhat.com>
Date:   Thu, 12 Mar 2020 15:05:38 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-tip-commits@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>, x86 <x86@...nel.org>
Subject: Re: [tip: irq/core] x86: Select HARDIRQS_SW_RESEND on x86

Hi,

On 3/12/20 3:02 PM, Linus Walleij wrote:
> On Thu, Mar 12, 2020 at 2:49 PM Hans de Goede <hdegoede@...hat.com> wrote:
> 
> [Me]
>>> I see that ARM and ARM64 simply just select this. What
>>> happens if you do that and why is x86 not selecting it in general?
>>
>> Erm, "selecting it in general" (well at least on x86) is what
>> this patch is doing.
> 
> Sorry that I was unclear, what I meant to say is why wasn't
> this done ages ago since so many important architectures seem
> to have it enabled by default.
> 
> I suppose the reason would be something like "firmware/BIOS
> should handle that for us" and recently that has started to
> break apart and x86 platforms started to be more like ARM?

That (x86 becoming more like ARM, sorta, kinda) as well as
that turning it on on x86 was not safe until Thomas wrote
the 2 patches which are marked as dependencies in the commit
message for this patch.

Regards,

Hans