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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 107B5C282C0 for ; Wed, 23 Jan 2019 10:32:05 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 4702620861 for ; Wed, 23 Jan 2019 10:32:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=ozlabs.org header.i=@ozlabs.org header.b="CmYqR/UJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4702620861 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ozlabs.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43l1my1pFjzDqNH for ; Wed, 23 Jan 2019 21:32:02 +1100 (AEDT) Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43l1kv4ZQKzDqKH for ; Wed, 23 Jan 2019 21:30:15 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=ozlabs.org header.i=@ozlabs.org header.b="CmYqR/UJ"; dkim-atps=neutral Received: by ozlabs.org (Postfix, from userid 1003) id 43l1kv0w4Wz9s4s; Wed, 23 Jan 2019 21:30:14 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ozlabs.org; s=201707; t=1548239415; bh=E9jhbke0ONEa9KRFA8tMqQVtg1nCTkEdmyAamgWd8wM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CmYqR/UJdoUIGevbgzvxg0kD6/8sBBn32/WNATH3c6fCIXpGZ0Y8I7EYgDnh+9W7+ fDkyvnz7VhEwiZbvT52Sws2Y/KVCFY0ZuzV9lWYoGfSYTV2610BZOdt0Zp4Fgn0FZd 7FO4yrJZOWO37tIlyeU+gFvlOsOJD4aWHEu5YPKG+Jo5l875LWZVF1Qk8CxLjlje8E VE6ZuSh8qjWm6CLNkOUxXeq/p/ejYcTI3ICpFu8zA2vYI2Gmua3mAShHF07J/4W+pi sZ8S3u52rbMaLK/xzLfswKvVhltZn9IiIqBywcMuqCDlf8N3C8CV/5b8FdFx/PPx9a UChxA2vFCohaA== Date: Wed, 23 Jan 2019 21:30:09 +1100 From: Paul Mackerras To: Benjamin Herrenschmidt Subject: Re: [PATCH 18/19] KVM: PPC: Book3S HV: add passthrough support Message-ID: <20190123103009.GB29826@blackberry> References: <20190107184331.8429-1-clg@kaod.org> <20190107191006.10648-1-clg@kaod.org> <20190107191006.10648-2-clg@kaod.org> <20190122052657.GG15124@blackberry> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, =?iso-8859-1?Q?C=E9dric?= Le Goater , linuxppc-dev@lists.ozlabs.org, David Gibson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Jan 23, 2019 at 05:45:24PM +1100, Benjamin Herrenschmidt wrote: > On Tue, 2019-01-22 at 16:26 +1100, Paul Mackerras wrote: > > On Mon, Jan 07, 2019 at 08:10:05PM +0100, Cédric Le Goater wrote: > > > Clear the ESB pages from the VMA of the IRQ being pass through to the > > > guest and let the fault handler repopulate the VMA when the ESB pages > > > are accessed for an EOI or for a trigger. > > > > Why do we want to do this? > > > > I don't see any possible advantage to removing the PTEs from the > > userspace mapping. You'll need to explain further. > > Afaik bcs we change the mapping to point to the real HW irq ESB page > instead of the "IPI" that was there at VM init time. So that makes it sound like there is a whole lot going on that hasn't even been hinted at in the patch descriptions... It sounds like we need a good description of how all this works and fits together somewhere under Documentation/. In any case we need much more informative patch descriptions. I realize that it's all currently in Cedric's head, but I bet that in two or three years' time when we come to try to debug something, it won't be in anyone's head... Paul.