linux-kernel - Re: [PATCH v8 01/33] x86/traps: let common_interrupt() handle IRQ_MOVE_CLEANUP

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Message-ID: <70ef07f1-e3b7-7c4e-01ac-11f159a87a6b@zytor.com>
Date:   Mon, 5 Jun 2023 10:09:23 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Thomas Gleixner <tglx@...utronix.de>, Xin Li <xin3.li@...el.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org
Cc:     mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        peterz@...radead.org, andrew.cooper3@...rix.com, seanjc@...gle.com,
        pbonzini@...hat.com, ravi.v.shankar@...el.com,
        jiangshanlai@...il.com, shan.kang@...el.com
Subject: Re: [PATCH v8 01/33] x86/traps: let common_interrupt() handle
 IRQ_MOVE_CLEANUP_VECTOR

On 6/5/23 10:07, Thomas Gleixner wrote:
> On Sat, Jun 03 2023 at 22:51, Thomas Gleixner wrote:
>> On Mon, Apr 10 2023 at 01:14, Xin Li wrote:
>>> IRQ_MOVE_CLEANUP_VECTOR is the only one of the system IRQ vectors that
>>> is *below* FIRST_SYSTEM_VECTOR. It is a slow path, so just push it
>>> into common_interrupt() just before the spurious interrupt handling.
>>
>> This is a complete NOOP on not FRED enabled systems as the IDT entry is
>> still separate. So this change makes no sense outside of the FRED
>> universe. Can we pretty please make this consistent?
> 
> The right thing to make this consistent is to get rid of this vector
> completely.
> 
> There is zero reason for this to be an IPI. This can be delegated to a
> worker or whatever delayed mechanism.
> 

As we discussed offline, I agree that this is a better solution (and 
should be a separate changeset before the FRED one.)

	-hpa