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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 95C66C0650F for ; Mon, 5 Aug 2019 11:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6D34620856 for ; Mon, 5 Aug 2019 11:38:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728565AbfHELiC (ORCPT ); Mon, 5 Aug 2019 07:38:02 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:9488 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727328AbfHELiB (ORCPT ); Mon, 5 Aug 2019 07:38:01 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x75BbRfx060185 for ; Mon, 5 Aug 2019 07:37:59 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2u6hn7xa2k-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 05 Aug 2019 07:37:59 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 5 Aug 2019 12:37:57 +0100 Received: from b06avi18626390.portsmouth.uk.ibm.com (9.149.26.192) by e06smtp02.uk.ibm.com (192.168.101.132) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 5 Aug 2019 12:37:51 +0100 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x75BbXBH31457760 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 5 Aug 2019 11:37:33 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DF22E4203F; Mon, 5 Aug 2019 11:37:50 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 69C0942042; Mon, 5 Aug 2019 11:37:50 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.152.224.51]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 5 Aug 2019 11:37:50 +0000 (GMT) Subject: Re: [RFC PATCH v2 07/19] RISC-V: KVM: Implement KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls To: Anup Patel , Palmer Dabbelt , Paul Walmsley , Paolo Bonzini , Radim K Cc: Daniel Lezcano , Thomas Gleixner , Atish Patra , Alistair Francis , Damien Le Moal , Christoph Hellwig , Anup Patel , "kvm@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" References: <20190802074620.115029-1-anup.patel@wdc.com> <20190802074620.115029-8-anup.patel@wdc.com> From: Christian Borntraeger Openpgp: preference=signencrypt Autocrypt: addr=borntraeger@de.ibm.com; prefer-encrypt=mutual; keydata= mQINBE6cPPgBEAC2VpALY0UJjGmgAmavkL/iAdqul2/F9ONz42K6NrwmT+SI9CylKHIX+fdf J34pLNJDmDVEdeb+brtpwC9JEZOLVE0nb+SR83CsAINJYKG3V1b3Kfs0hydseYKsBYqJTN2j CmUXDYq9J7uOyQQ7TNVoQejmpp5ifR4EzwIFfmYDekxRVZDJygD0wL/EzUr8Je3/j548NLyL 4Uhv6CIPf3TY3/aLVKXdxz/ntbLgMcfZsDoHgDk3lY3r1iwbWwEM2+eYRdSZaR4VD+JRD7p8 0FBadNwWnBce1fmQp3EklodGi5y7TNZ/CKdJ+jRPAAnw7SINhSd7PhJMruDAJaUlbYaIm23A +82g+IGe4z9tRGQ9TAflezVMhT5J3ccu6cpIjjvwDlbxucSmtVi5VtPAMTLmfjYp7VY2Tgr+ T92v7+V96jAfE3Zy2nq52e8RDdUo/F6faxcumdl+aLhhKLXgrozpoe2nL0Nyc2uqFjkjwXXI OBQiaqGeWtxeKJP+O8MIpjyGuHUGzvjNx5S/592TQO3phpT5IFWfMgbu4OreZ9yekDhf7Cvn /fkYsiLDz9W6Clihd/xlpm79+jlhm4E3xBPiQOPCZowmHjx57mXVAypOP2Eu+i2nyQrkapaY IdisDQfWPdNeHNOiPnPS3+GhVlPcqSJAIWnuO7Ofw1ZVOyg/jwARAQABtDRDaHJpc3RpYW4g Qm9ybnRyYWVnZXIgKElCTSkgPGJvcm50cmFlZ2VyQGRlLmlibS5jb20+iQI4BBMBAgAiBQJO nDz4AhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRARe7yAtaYcfOYVD/9sqc6ZdYKD bmDIvc2/1LL0g7OgiA8pHJlYN2WHvIhUoZUIqy8Sw2EFny/nlpPVWfG290JizNS2LZ0mCeGZ 80yt0EpQNR8tLVzLSSr0GgoY0lwsKhAnx3p3AOrA8WXsPL6prLAu3yJI5D0ym4MJ6KlYVIjU ppi4NLWz7ncA2nDwiIqk8PBGxsjdc/W767zOOv7117rwhaGHgrJ2tLxoGWj0uoH3ZVhITP1z gqHXYaehPEELDV36WrSKidTarfThCWW0T3y4bH/mjvqi4ji9emp1/pOWs5/fmd4HpKW+44tD Yt4rSJRSa8lsXnZaEPaeY3nkbWPcy3vX6qafIey5d8dc8Uyaan39WslnJFNEx8cCqJrC77kI vcnl65HaW3y48DezrMDH34t3FsNrSVv5fRQ0mbEed8hbn4jguFAjPt4az1xawSp0YvhzwATJ YmZWRMa3LPx/fAxoolq9cNa0UB3D3jmikWktm+Jnp6aPeQ2Db3C0cDyxcOQY/GASYHY3KNra z8iwS7vULyq1lVhOXg1EeSm+lXQ1Ciz3ub3AhzE4c0ASqRrIHloVHBmh4favY4DEFN19Xw1p 76vBu6QjlsJGjvROW3GRKpLGogQTLslbjCdIYyp3AJq2KkoKxqdeQYm0LZXjtAwtRDbDo71C FxS7i/qfvWJv8ie7bE9A6Wsjn7kCDQROnDz4ARAAmPI1e8xB0k23TsEg8O1sBCTXkV8HSEq7 JlWz7SWyM8oFkJqYAB7E1GTXV5UZcr9iurCMKGSTrSu3ermLja4+k0w71pLxws859V+3z1jr nhB3dGzVZEUhCr3EuN0t8eHSLSMyrlPL5qJ11JelnuhToT6535cLOzeTlECc51bp5Xf6/XSx SMQaIU1nDM31R13o98oRPQnvSqOeljc25aflKnVkSfqWSrZmb4b0bcWUFFUKVPfQ5Z6JEcJg Hp7qPXHW7+tJTgmI1iM/BIkDwQ8qe3Wz8R6rfupde+T70NiId1M9w5rdo0JJsjKAPePKOSDo RX1kseJsTZH88wyJ30WuqEqH9zBxif0WtPQUTjz/YgFbmZ8OkB1i+lrBCVHPdcmvathknAxS bXL7j37VmYNyVoXez11zPYm+7LA2rvzP9WxR8bPhJvHLhKGk2kZESiNFzP/E4r4Wo24GT4eh YrDo7GBHN82V4O9JxWZtjpxBBl8bH9PvGWBmOXky7/bP6h96jFu9ZYzVgIkBP3UYW+Pb1a+b w4A83/5ImPwtBrN324bNUxPPqUWNW0ftiR5b81ms/rOcDC/k/VoN1B+IHkXrcBf742VOLID4 YP+CB9GXrwuF5KyQ5zEPCAjlOqZoq1fX/xGSsumfM7d6/OR8lvUPmqHfAzW3s9n4lZOW5Jfx bbkAEQEAAYkCHwQYAQIACQUCTpw8+AIbDAAKCRARe7yAtaYcfPzbD/9WNGVf60oXezNzSVCL hfS36l/zy4iy9H9rUZFmmmlBufWOATjiGAXnn0rr/Jh6Zy9NHuvpe3tyNYZLjB9pHT6mRZX7 Z1vDxeLgMjTv983TQ2hUSlhRSc6e6kGDJyG1WnGQaqymUllCmeC/p9q5m3IRxQrd0skfdN1V AMttRwvipmnMduy5SdNayY2YbhWLQ2wS3XHJ39a7D7SQz+gUQfXgE3pf3FlwbwZhRtVR3z5u aKjxqjybS3Ojimx4NkWjidwOaUVZTqEecBV+QCzi2oDr9+XtEs0m5YGI4v+Y/kHocNBP0myd pF3OoXvcWdTb5atk+OKcc8t4TviKy1WCNujC+yBSq3OM8gbmk6NwCwqhHQzXCibMlVF9hq5a FiJb8p4QKSVyLhM8EM3HtiFqFJSV7F+h+2W0kDyzBGyE0D8z3T+L3MOj3JJJkfCwbEbTpk4f n8zMboekuNruDw1OADRMPlhoWb+g6exBWx/YN4AY9LbE2KuaScONqph5/HvJDsUldcRN3a5V RGIN40QWFVlZvkKIEkzlzqpAyGaRLhXJPv/6tpoQaCQQoSAc5Z9kM/wEd9e2zMeojcWjUXgg oWj8A/wY4UXExGBu+UCzzP/6sQRpBiPFgmqPTytrDo/gsUGqjOudLiHQcMU+uunULYQxVghC syiRa+UVlsKmx1hsEg== Date: Mon, 5 Aug 2019 13:37:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190802074620.115029-8-anup.patel@wdc.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19080511-0008-0000-0000-0000030562E6 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19080511-0009-0000-0000-0000A17F67EC Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-05_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=776 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908050131 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02.08.19 09:47, Anup Patel wrote: > For KVM RISC-V, we use KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls to access > VCPU config and registers from user-space. > > We have three types of VCPU registers: > 1. CONFIG - these are VCPU config and capabilities > 2. CORE - these are VCPU general purpose registers > 3. CSR - these are VCPU control and status registers > > The CONFIG registers available to user-space are ISA and TIMEBASE. Out > of these, TIMEBASE is a read-only register which inform user-space about > VCPU timer base frequency. The ISA register is a read and write register > where user-space can only write the desired VCPU ISA capabilities before > running the VCPU. > > The CORE registers available to user-space are PC, RA, SP, GP, TP, A0-A7, > T0-T6, S0-S11 and MODE. Most of these are RISC-V general registers except > PC and MODE. The PC register represents program counter whereas the MODE > register represent VCPU privilege mode (i.e. S/U-mode). > > The CSRs available to user-space are SSTATUS, SIE, STVEC, SSCRATCH, SEPC, > SCAUSE, STVAL, SIP, and SATP. All of these are read/write registers. > > In future, more VCPU register types will be added (such as FP) for the > KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls. While have ONE_REG will certainly work, have you considered the sync_reg scheme (registers as part of kvm_run structure) This will speed up the exit to QEMU as you do not have to do multiple ioctls (each imposing a systemcall overhead) for one exit. Ideally you should not exit too often into qemu, but for those cases sync_regs is faster than ONE_REG.