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=-4.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 6E93EC2B9F4 for ; Tue, 22 Jun 2021 17:34:29 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3633F61107 for ; Tue, 22 Jun 2021 17:34:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3633F61107 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Subject:Cc:To:From:Message-ID:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=/kSCukZpnxk+SR5zPNGOnH7duB27Pya6rrbDAcs/Dmo=; b=I9Pxh2DfxcZ4Kk 8iC8vwi8mDW5g4lTQQI+AZyLYzszkLhG2I2UHsM48GgmGRnZlesYK4hvPIwugdsHmt2coArzesWqc tM0frB/4IROr2SJdHZw3UNzdAvm4pQJiRJt/638PtvFmpbWp2vru7DvNZ/v5NLw7YbRQAXakC5UMO mXTCkc2+oeitWL33Xnk0XHH6qD6FmlhW19QKkpTfxzP6MClwMx+/NPWdgIEwJkRcswEAGVS2H4Vga ency0VBLFimvW9x5p8eX1d9sgphiq4X872T2tuRF2sECoQtby3+8bo2G7pJqxbMSy7ZSe1PAO6qDy irQj1nA6VFA6XHzTzi2Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lvkGc-0083XE-Gq; Tue, 22 Jun 2021 17:32:54 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lvkGY-0083WF-6n for linux-arm-kernel@lists.infradead.org; Tue, 22 Jun 2021 17:32:51 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F2CDD61075; Tue, 22 Jun 2021 17:32:49 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lvkGV-009E0J-Re; Tue, 22 Jun 2021 18:32:48 +0100 Date: Tue, 22 Jun 2021 18:32:47 +0100 Message-ID: <87sg19by9s.wl-maz@kernel.org> From: Marc Zyngier To: Boqun Feng Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, Arnd Bergmann , Bjorn Helgaas , Linux ARM , Catalin Marinas , Will Deacon Subject: Re: [RFC 0/2] irqchip/gic-v3-its: Introduce virtual ITS In-Reply-To: <20210622155313.3819952-1-boqun.feng@gmail.com> References: <20210622155313.3819952-1-boqun.feng@gmail.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: boqun.feng@gmail.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, arnd@arndb.de, bhelgaas@google.com, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210622_103250_303608_C550959E X-CRM114-Status: GOOD ( 24.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 22 Jun 2021 16:53:11 +0100, Boqun Feng wrote: > > Hi Marc, > > Here is an RFC for supporting platforms having LPI supported but without > ITS. And this is for the virtual PCI support for ARM64 Hyper-V guests. > We currently choose this approach (LPI w/o ITS) because a) it's allowed > for GICv3 and b) ITS may not be a more efficient way to configure LPIs > compared to hypercalls, but we'd like to get feedbacks from the > community. > > Besides, patch #1 fixes a bug which I found while I was at it. > > Looking forwards to any comment and suggestion! My suggestion is to not do that. The ITS driver is used to drive an ITS. That, and only that. The simple fact that you mention hypercalls shows that this is *not* what the architecture allows. So if you are going to implement something that is evidently outside of the scope of the architecture, keep it in some Hyper-V specific code that doesn't involve the ITS driver. All you need is something that will piggy-back on top of the GIC driver using a hierarchical driver. We support that today. Of course, you'll have to invent your own firmware interface for discovery. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel