linux-kernel - Re: [PATCH v8 29/33] x86/fred: allow FRED systems to use interrupt vectors 0x10-0x1f

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Message-ID: <87zg5e57go.ffs@tglx>
Date:   Mon, 05 Jun 2023 16:06:47 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     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,
        hpa@...or.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 29/33] x86/fred: allow FRED systems to use interrupt
 vectors 0x10-0x1f

On Mon, Apr 10 2023 at 01:14, Xin Li wrote:
> From: "H. Peter Anvin (Intel)" <hpa@...or.com>
>
> FRED inherits the Intel VT-x enhancement of classified events with
> a two-level event dispatch logic. The first-level dispatch is on
> the event type, and the second-level is on the event vector. This
> also means that vectors in different event types are orthogonal,
> thus, vectors 0x10-0x1f become available as hardware interrupts.
>
> Enable interrupt vectors 0x10-0x1f on FRED systems (interrupt 0x80 is
> already enabled.) Most of these changes are about removing the
> assumption that the lowest-priority vector is hard-wired to 0x20.

I'm not really interested in this again premature optimization.

Can we please clarify how the final result of FRED vector layout will
look like?

I rather give up on reclaiming these 16 vectors than making _all_ system
vectors dynamically assignable to avoid an extra partitioning of the
vector space.

Thanks,

        tglx