linux-kernel - Re: [PATCH v2 05/13] x86/irq: Reserve a per CPU IDT vector for posted MSIs

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Message-ID: <20240422153250.07331f49@jacob-builder>
Date: Mon, 22 Apr 2024 15:32:50 -0700
From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, LKML
 <linux-kernel@...r.kernel.org>, X86 Kernel <x86@...nel.org>, Peter Zijlstra
 <peterz@...radead.org>, iommu@...ts.linux.dev, Lu Baolu
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 <dave.hansen@...el.com>, Joerg Roedel <joro@...tes.org>, "H. Peter Anvin"
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 <ashok.raj@...el.com>, "Tian, Kevin" <kevin.tian@...el.com>,
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 kan.liang@...el.com, "Kleen, Andi" <andi.kleen@...el.com>,
 jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 05/13] x86/irq: Reserve a per CPU IDT vector for
 posted MSIs

Hi Arnaldo,

On Fri, 19 Apr 2024 17:07:17 -0300, Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:

> > > On a second thought, if we make system IRQ vector determined at
> > > compile time based on different CONFIG options, will it break
> > > userspace tools such as perf? More importantly the rule of not
> > > breaking userspace.  
> 
> The rule for tools/perf is "don't impose _any requirement_ on the kernel
> developers, they don't have to test if any change they do outside of
> tools/ will break something inside tools/."
>  
> > tools/arch/x86/include/asm/irq_vectors.h is only used to generate the
> > list of system vectors for pretty output. And your change already broke
> > that.  
> 
> Yeah, I even moved that from tools/arch/x86/include/asm/irq_vectors.h
> to tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h (for next
> merge window).

So I will not add anything to the tools directory for my next version.
Just a heads-up for adding this new vector.

Thanks,

Jacob