linux-kernel - Re: [PATCH v5 01/23] irqchip/gic-v3: Use SGIs without active state if offered

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Message-ID: <63f6530a-9369-31e6-88d0-5337173495b9@huawei.com>
Date:   Thu, 12 Mar 2020 14:30:28 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Marc Zyngier <maz@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Robert Richter <rrichter@...vell.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Eric Auger <eric.auger@...hat.com>,
        "James Morse" <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH v5 01/23] irqchip/gic-v3: Use SGIs without active state if
 offered

Hi Marc,

On 2020/3/5 4:33, 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).

I still can't find the description of these two bits in IHI0069F.
Are they actually architected and will be available in the future
version of the spec?  I want to confirm it again since this has a
great impact on the KVM code, any pointers?


Thanks,
Zenghui