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=-2.2 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 327E0C432C2 for ; Tue, 24 Sep 2019 06:50:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0973C21655 for ; Tue, 24 Sep 2019 06:50:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728221AbfIXGua (ORCPT ); Tue, 24 Sep 2019 02:50:30 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:63014 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727669AbfIXGua (ORCPT ); Tue, 24 Sep 2019 02:50:30 -0400 Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x8O6ltTK114369 for ; Tue, 24 Sep 2019 02:50:30 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2v7ddx9j4p-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 24 Sep 2019 02:50:29 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 24 Sep 2019 07:50:22 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x8O6oLmx56557688 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 24 Sep 2019 06:50:21 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A9216AE04D; Tue, 24 Sep 2019 06:50:21 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 35940AE053; Tue, 24 Sep 2019 06:50:21 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.152.224.146]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 24 Sep 2019 06:50:21 +0000 (GMT) Subject: Re: [RFC patch 00/15] entry: Provide generic implementation for host and guest entry/exit work To: Thomas Gleixner , LKML Cc: x86@kernel.org, Peter Zijlstra , Andy Lutomirski , Catalin Marinas , Will Deacon , Mark Rutland , Marc Zyngier , Paolo Bonzini , kvm@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390 References: <20190919150314.054351477@linutronix.de> From: Christian Borntraeger Openpgp: preference=signencrypt Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190919150314.054351477@linutronix.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19092406-0012-0000-0000-0000034FDE95 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19092406-0013-0000-0000-0000218A6D23 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-09-24_04:,, 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=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909240067 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 19.09.19 17:03, Thomas Gleixner wrote: > When working on a way to move out the posix cpu timer expiry out of the > timer interrupt context, I noticed that KVM is not handling pending task > work before entering a guest. A quick hack was to add that to the x86 KVM > handling loop. The discussion ended with a request to make this a generic > infrastructure possible with also moving the per arch implementations of > the enter from and return to user space handling generic. > > https://lore.kernel.org/r/89E42BCC-47A8-458B-B06A-D6A20D20512C@amacapital.net > > You asked for it, so don't complain that you have to review it :) > > The series implements the syscall enter/exit and the general exit to > userspace work handling along with the pre guest enter functionality. > > The series converts x86 and ARM64. x86 is fully tested including selftests > etc. ARM64 is only compile tested for now as my only ARM64 testbox is not > available right now. It seems that s390x would also need to look into TIF_NOTIFY_PENDING before entering a KVM guest. Given that the s390x entry path is still in assembler this might not be something to do quickly. Would it make sense to actually start with a minimal solution (e.g. one that provides notify_resume_pending like your original patch) as a fix. That would also be simple to backport. And then we can do the proper rework on top. Or do we consider anything that depends on TIF_NOTIFY_PENDING before entering a guest as not important enough for stable? After all the vcpu_run ioctl almost never returns to userspace and nothing was obviously broken. Another question: Are there callbacks due to TIF_NOTIFY_PENDING that should NOT happen as long as we stay in the vpcu loop?