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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 96A7EC12002 for ; Wed, 21 Jul 2021 08:32:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78CB56120A for ; Wed, 21 Jul 2021 08:32:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237265AbhGUHvi (ORCPT ); Wed, 21 Jul 2021 03:51:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:46640 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236383AbhGUHmb (ORCPT ); Wed, 21 Jul 2021 03:42:31 -0400 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 46F786120A; Wed, 21 Jul 2021 08:23:02 +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 1m67VM-00Eev3-8O; Wed, 21 Jul 2021 09:23:00 +0100 Date: Wed, 21 Jul 2021 09:22:44 +0100 Message-ID: <87im142i0b.wl-maz@kernel.org> From: Marc Zyngier To: Sergey Senozhatsky Cc: Will Deacon , Suleiman Souhlal , Joel Fernandes , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCHv2 2/4] arm64: add guest pvstate support In-Reply-To: References: <20210709043713.887098-1-senozhatsky@chromium.org> <20210709043713.887098-3-senozhatsky@chromium.org> <877dhv35ea.wl-maz@kernel.org> 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") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: senozhatsky@chromium.org, will@kernel.org, suleiman@google.com, joelaf@google.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Jul 2021 03:05:25 +0100, Sergey Senozhatsky wrote: > > On (21/07/12 16:42), Marc Zyngier wrote: > > > > > > PV-vcpu-state is a per-CPU struct, which, for the time being, > > > holds boolean `preempted' vCPU state. During the startup, > > > given that host supports PV-state, each guest vCPU sends > > > a pointer to its per-CPU variable to the host as a payload > > > > What is the expected memory type for this memory region? What is its > > life cycle? Where is it allocated from? > > Guest per-CPU area, which physical addresses is shared with the > host. Again: what are the memory types you expect this to be used with? When will the hypervisor ever stop accessing this? How does it work across reset? I'm sorry to be that pressing, but these are the gory details that actually matter if you want this thing to be maintainable. Thanks, M. -- Without deviation from the norm, progress is not possible.