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Date:   Mon, 17 Feb 2020 17:18:10 +0800
From:   Zenghui Yu <>
To:     Marc Zyngier <>,
        <>, <>,
CC:     Lorenzo Pieralisi <>,
        Jason Cooper <>,
        Robert Richter <>,
        "Thomas Gleixner" <>,
        Eric Auger <>,
        "James Morse" <>,
        Julien Thierry <>,
        Suzuki K Poulose <>
Subject: Re: [PATCH v4 02/20] irqchip/gic-v3: Use SGIs without active state if

Hi Marc,

On 2020/2/14 22:57, Marc Zyngier wrote:
> To allow the direct injection of SGIs into a guest, the GICv4.1
> architecture has to sacrifice the Active state so that SGIs look
> a lot like LPIs (they are injected by the same mechanism).
> In order not to break existing software, the architecture gives
> offers guests OSs the choice: SGIs with or without an active
> state. It is the hypervisors duty to honor the guest's choice.
> For this, the architecture offers a discovery bit indicating whether
> the GIC supports GICv4.1 SGIs (GICD_TYPER2.nASSGIcap), and another
> bit indicating whether the guest wants Active-less SGIs or not
> (controlled by GICD_CTLR.nASSGIreq).
> A hypervisor not supporting GICv4.1 SGIs would leave nASSGIcap
> clear, and a guest not knowing about GICv4.1 SGIs (or definitely
> wanting an Active state) would leave nASSGIreq clear (both being
> thankfully backward compatible with oler revisions of the GIC).

> Since Linux is perfectly happy without an active state on SGIs,
> inform the hypervisor that we'll use that if offered.
> Signed-off-by: Marc Zyngier <>

Per the description of these two bits in the commit message,

Reviewed-by: Zenghui Yu <>


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