From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDD2EC7619D for ; Mon, 17 Feb 2020 09:18:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6BC12070B for ; Mon, 17 Feb 2020 09:18:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728815AbgBQJSX (ORCPT ); Mon, 17 Feb 2020 04:18:23 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:10626 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728272AbgBQJSX (ORCPT ); Mon, 17 Feb 2020 04:18:23 -0500 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 8B5BF7C85E4B5CC973CB; Mon, 17 Feb 2020 17:18:18 +0800 (CST) Received: from [127.0.0.1] (10.173.222.27) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.439.0; Mon, 17 Feb 2020 17:18:11 +0800 Subject: Re: [PATCH v4 02/20] irqchip/gic-v3: Use SGIs without active state if offered To: Marc Zyngier , , , , CC: Lorenzo Pieralisi , Jason Cooper , Robert Richter , "Thomas Gleixner" , Eric Auger , "James Morse" , Julien Thierry , Suzuki K Poulose References: <20200214145736.18550-1-maz@kernel.org> <20200214145736.18550-3-maz@kernel.org> From: Zenghui Yu Message-ID: Date: Mon, 17 Feb 2020 17:18:10 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20200214145736.18550-3-maz@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.222.27] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). older? > > 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 Thanks