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 402DFC433FE for ; Fri, 25 Mar 2022 10:23:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354590AbiCYKZD (ORCPT ); Fri, 25 Mar 2022 06:25:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40590 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345973AbiCYKZB (ORCPT ); Fri, 25 Mar 2022 06:25:01 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 66C335F4C7 for ; Fri, 25 Mar 2022 03:23:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648203806; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FqCkuUzPjL3vvNWJz+rpLQdGrzF6nE10Um+x1rzjlhw=; b=eycqUu+lmTpWohdjgA/uorq8UagF7J0eLotCDJ0DSPQEYv953ODxIWnPpERwwQB78Ddf2z OR3rwmzYbzCa76CricdWC5dAW3oDDJzKGFL0uF5q9Z+4G3YkrhutizbmdzPgdwY2Wcpvf+ 87/pAbq8lFJ3lfOlUpvxwQ1G4YxYHag= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-498-4BHchNMkNC6H0D-e-9kIow-1; Fri, 25 Mar 2022 06:23:22 -0400 X-MC-Unique: 4BHchNMkNC6H0D-e-9kIow-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5387B802803; Fri, 25 Mar 2022 10:23:22 +0000 (UTC) Received: from [10.72.12.33] (ovpn-12-33.pek2.redhat.com [10.72.12.33]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C5CC840D296B; Fri, 25 Mar 2022 10:23:17 +0000 (UTC) Reply-To: Gavin Shan Subject: Re: [PATCH v5 19/22] KVM: arm64: Support SDEI ioctl commands on vCPU To: Oliver Upton 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 References: <20220322080710.51727-1-gshan@redhat.com> <20220322080710.51727-20-gshan@redhat.com> <949146db-d467-4949-9e82-94f803c3b166@redhat.com> From: Gavin Shan Message-ID: Date: Fri, 25 Mar 2022 18:23:14 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Oliver, On 3/25/22 4:37 PM, Oliver Upton wrote: > On Fri, Mar 25, 2022 at 03:59:50PM +0800, Gavin Shan wrote: >> 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 :) > Ok, Thanks for your clarification about 'one giant pseudoregister'. Lets have more discussion about the migration on next revision. To be more clear, I plan to implement the base functionality, where only the private event is supported. After it reaches into mergeable or merged, we can post the add-on series to support migration. >> 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. > Ok, I think we need padding to structures of the event, to make the event object aligned to 64-bytes aligned, and VCPU state to 512-bytes aligned. 64-bytes and 128-bytes registers have been supported. Thanks, Gavin