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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D23A7C433EF for ; Fri, 25 Mar 2022 08:38:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355301AbiCYIjf (ORCPT ); Fri, 25 Mar 2022 04:39:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351420AbiCYIje (ORCPT ); Fri, 25 Mar 2022 04:39:34 -0400 Received: from mail-il1-x12a.google.com (mail-il1-x12a.google.com [IPv6:2607:f8b0:4864:20::12a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6DA0FCD312 for ; Fri, 25 Mar 2022 01:38:00 -0700 (PDT) Received: by mail-il1-x12a.google.com with SMTP id j15so4741481ila.13 for ; Fri, 25 Mar 2022 01:38:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=9k7Y8WevncKwpBhN8GfDJPtpTXD3hrhwGt8wNGgKE88=; b=kJla5xL5682VRhITm7mYpJSv9xA9f20EYy0FOb4lmRJ066bsONolddlq/nDZsS4qWo 2Bt9vcCBjbPhDlVY0oyvJavLRj9bI1ArzI5Rm+Z7ke8cj87XhsmPgWO23LLnzZ/WMUc8 q9f13beidyvk7D71B9sc4ctKwiUEKWYlJFqs91ZM4KLOOsIRp7RNwr0zd1uqU7PqmHbe VVoRwef+mProrNYGLhVLAbi23Fmzuer5EAFDs0I69UE0jRJ8cb1yBZaYhZ+czqTCKKM+ /cxjfaWlopTIwU6JKrOi7NKANp5xsx8PmlbgrnKVXf0jvLPq3IGDH7RtEntiWpSIUgBb G7iQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9k7Y8WevncKwpBhN8GfDJPtpTXD3hrhwGt8wNGgKE88=; b=0dVTNq7QPwmn+NtlElfvhjMg7ArOnT4cqfqG45q+HP09BRO6tm3uGTo0bciTqlWUFf qt5jncWtOUHI3H755XaUmcbgFKGuNi2YkY7pjupJ1MtTc64U2v4MVfRRQxejrwaOeSZW 8YUaR6mbK2y5sxxeQNTwIJiRf9E4MdrpFulnfQHUg72s/AZpGm7jblTX+YOPUjwoHty4 aHwg/Dv2yvukxiqGzcDXIjiP+BLv/yiM2SqydZe+yrs3DkLKpUkmmZOiDw6loPSSux+F rCaN+D7c0Vk6ZpInQPtRfDbhyRJIJPLXP6maQUseJVwIk6+477xx0CWvBZiK/FLbhTw8 Ezhw== X-Gm-Message-State: AOAM533qAWRsTtkYpoAt+d/P/I8mkrzmf/pSS1nKic/vmpwVAbMdfKbB XHe1aYic1wXRYp2kaO1Sl1e3Bka+Fejhzg== X-Google-Smtp-Source: ABdhPJyJC/YiQb6vlBS9ZFN2J20kwUvAt30H61gUwhYDFICPDSxDuwwh3f3X9GJ3e+aSc/EZEZufQQ== X-Received: by 2002:a05:6e02:2162:b0:2c8:47b8:d3e1 with SMTP id s2-20020a056e02216200b002c847b8d3e1mr4875222ilv.59.1648197479512; Fri, 25 Mar 2022 01:37:59 -0700 (PDT) Received: from google.com (194.225.68.34.bc.googleusercontent.com. [34.68.225.194]) by smtp.gmail.com with ESMTPSA id v3-20020a5d9483000000b00640d3d4acabsm2593820ioj.44.2022.03.25.01.37.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Mar 2022 01:37:58 -0700 (PDT) Date: Fri, 25 Mar 2022 08:37:55 +0000 From: Oliver Upton To: Gavin Shan Cc: kvmarm@lists.cs.columbia.edu, maz@kernel.org, linux-kernel@vger.kernel.org, eauger@redhat.com, shan.gavin@gmail.com, Jonathan.Cameron@huawei.com, pbonzini@redhat.com, vkuznets@redhat.com, will@kernel.org Subject: Re: [PATCH v5 19/22] KVM: arm64: Support SDEI ioctl commands on vCPU Message-ID: References: <20220322080710.51727-1-gshan@redhat.com> <20220322080710.51727-20-gshan@redhat.com> <949146db-d467-4949-9e82-94f803c3b166@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <949146db-d467-4949-9e82-94f803c3b166@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 25, 2022 at 03:59:50PM +0800, Gavin Shan wrote: > Hi Oliver, > > On 3/24/22 1:55 AM, Oliver Upton wrote: > > On Tue, Mar 22, 2022 at 04:07:07PM +0800, Gavin Shan wrote: > > > This supports ioctl commands on vCPU to manage the various object. > > > It's primarily used by VMM to accomplish migration. The ioctl > > > commands introduced by this are highlighted as below: > > > > > > * KVM_SDEI_CMD_GET_VCPU_EVENT_COUNT > > > Return the total count of vCPU events, which have been queued > > > on the target vCPU. > > > > > > * KVM_SDEI_CMD_GET_VCPU_EVENT > > > * KVM_SDEI_CMD_SET_VCPU_EVENT > > > Get or set vCPU events. > > > > > > * KVM_SDEI_CMD_GET_VCPU_STATE > > > * KVM_SDEI_CMD_SET_VCPU_STATE > > > Get or set vCPU state. > > > > All of this GET/SET stuff can probably be added to KVM_{GET,SET}_ONE_REG > > immediately. Just introduce new registers any time a new event comes > > along. The only event we have at the end of this series is the > > software-signaled event, with async PF coming later right? > > > > Some special consideration is likely necessary to avoid adding a > > register for every u64 chunk of data. I don't think we need to afford > > userspace any illusion of granularity with these, and can probably lump > > it all under one giant pseudoregister. > > > > Yes, KVM_{GET,SET}_ONE_REG is the ideal interface for migration. You're > correct we're only concerned by software signaled event and the one for > Async PF. > > I didn't look into Raghavendra's series deeply. Actually, a lump of > registers can be avoid after 2048 byte size is specified in its > encoding. I think 2048 bytes are enough for now since there are > only two supported events. When I had said 'one giant pseudoregister' I actually meant 'one pseudoregister per event', not all of SDEI into a single structure. Since most of this is in flux now, it is hard to point out what/how we should migrate from conversation alone. And on the topic of Raghavendra's series, I do not believe it is required anymore here w/ the removal of shared events, which I'm strongly in favor of. Let's delve deeper into migration on the next series :) > In the future, we probably have varied number of SDEI events to > be migrated. In that case, we need to add a new bit to the encoding > of the pseudo system register, so that VMM (QEMU) can support > variable sized system register and keep reading and writing on > these registers on migration: > > PSEUDO_SDEI_ADDR: 64-bits in width > PSEUDO_SDEI_DATA: has varied size > > PSEUDO_SDEI_ADDR is used to (1) Indicate the size of PSEUDO_SDEI_DATA > (2) The information to be read/written, for example the (shared/private) > registered events on VM and vCPU, VCPU state. > > PSEUDO_SDEI_DATA is used to (1) Retrieved information or that to be > written. (2) Flags to indicate current block of information is the > last one or not. I don't think we have sufficient encoding space in the register ID to allow for arbitrary length registers. Any new registers for SDEI will need to fit into one of the predefined sizes. Note that we've already conditioned userspace to handle registers this way and anything else is an ABI change. -- Thanks, Oliver